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{
"id": 315000,
"topic": "gcn.circulars",
"uuid": "3cc8823e-5b2b-4f61-83cd-ec761a70803c",
"title": "EP250526a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40554"
},
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"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40554....1W",
"eventId": "EP250526a",
"subject": "EP250526a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1748349871308,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40554,
"submittedHow": "web"
},
"message_text": "Jiahua Wu (GZHU), D. Y. Li (NAO, CAS), B.-T. Wang (YNAO, CAS), W. F. Wen (SZTU) and Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team:\n\nThe X-ray transient EP250526a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Li et al., GCN 40550), and followed up by several optical telescopes (Lipunov et al, GCN 40551, Angulo et al., GCN 40552), while no optical counterpart has been detected yet. Refined analysis of the WXT data shows that the event started at T0=2025-05-26T19:24:55 (UTC) and lasted for about 175 s (T90). The peak flux (0.5-4 keV) is estimated to be 4 x 10^-9 erg/s/cm^2 (T0+39 s). The averaged 0.5-4 keV spectrum of T90 can be fitted with an absorbed power-law with a Galactic hydrogen column density of 7 x 10^20 cm^-2 and a photon index of 1.31 (-/+0.42). The derived average unabsorbed 0.5-4 keV flux is 1.75 (-0.37, +0.51) x 10^-9 erg/s/cm^2. \n\nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-05-26T19:31:10, about 375 seconds after T0, with an exposure time of 2270 seconds. The averaged 0.5-10 keV spectrum can be fitted with an absorbed power-law with a photon index of 2.59 (-0.43, +0.44). The derived unabsorbed 0.5-10 keV flux is 7.0 (-1.4, +2.0) x 10^-13 erg/s/cm^2. Another FXT observation was conducted at 2025-05-27T04:18:56, about 9 hours after T0. The X-ray spectrum can be fitted with an absorbed power-law with a photon index of 2.37 (-0.93, +0.91), and the derived unabsorbed 0.5-10 keV flux is 1.2 (-0.5, +1.2) x 10^-13 erg/s/cm^2. The absorption was fixed at the Galactic value during the spectral fitting. The uncertainties are at the 90% confidence level for the above parameters.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). \n\nThe contact TA of this source is Jiahua Wu, please contact him via the email jhwu@e.gzhu.edu.cn if needed.",
"published": "2025-06-29T06:22:09.081863Z",
"message_parser": "GCN Circular Parser v2",
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{
"id": 199523,
"topic": "gcn.circulars",
"uuid": "a3cc3a1c-2e20-4925-b43c-e469fa52752c",
"title": "EP250526a: SVOM/VT optical upper limit",
"submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"authors": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"data": {
"urls": {
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"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250526a",
"subject": "EP250526a: SVOM/VT optical upper limit",
"createdOn": 1748437143822,
"submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"circularId": 40562,
"submittedHow": "web"
},
"message_text": "L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, D. Y. Li (NAO, CAS), B.-T. Wang (YNAO, CAS), W. F. Wen (SZTU), J. H. Wu (GZHU), Y. Liu (NAO, CAS) report on behalf of the SVOM and EP mission team\n\nSVOM/VT conducted ToO follow-up observations of the EP250526a (Li et al., GCN 40550, Wu et al., GCN 40554). The observation started on 2025-05-27T04:04:19 UT (i.e. 7.66 hour after trigger time) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. \n\nNo uncatalogued source was detected, compared to the Legacy survey, within errorbox of EP-FXT (Li et al., GCN 40550), down to 3 sigma upper limit of VT_R~23.0 mag (AB) in 16*70 sec stacked images at the mid time of 7.81 hour.\n\nThe upper limit is consistent with the reports(Lipunov et al., GCN 40551, Angulo et al., GCN 40552).\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n\n",
"published": "2025-05-28T12:59:11.771763Z",
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"created": "2025-05-28T12:59:11.771778Z",
"modified": "2025-05-28T12:59:11.793393Z",
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{
"id": 202946,
"topic": "gcn.circulars",
"uuid": "80d85d61-f5dc-4cbd-aa7c-dd14613a4256",
"title": "EP250526a: SVOM/VT optical upper limit",
"submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"authors": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
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"bibcode": "2025GCN.40562....1X",
"eventId": "EP250526a",
"subject": "EP250526a: SVOM/VT optical upper limit",
"createdOn": 1748437143822,
"submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"circularId": 40562,
"submittedHow": "web"
},
"message_text": "L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, D. Y. Li (NAO, CAS), B.-T. Wang (YNAO, CAS), W. F. Wen (SZTU), J. H. Wu (GZHU), Y. Liu (NAO, CAS) report on behalf of the SVOM and EP mission team\n\nSVOM/VT conducted ToO follow-up observations of the EP250526a (Li et al., GCN 40550, Wu et al., GCN 40554). The observation started on 2025-05-27T04:04:19 UT (i.e. 7.66 hour after trigger time) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. \n\nNo uncatalogued source was detected, compared to the Legacy survey, within errorbox of EP-FXT (Li et al., GCN 40550), down to 3 sigma upper limit of VT_R~23.0 mag (AB) in 16*70 sec stacked images at the mid time of 7.81 hour.\n\nThe upper limit is consistent with the reports(Lipunov et al., GCN 40551, Angulo et al., GCN 40552).\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n\n",
"published": "2025-06-09T08:08:56.252495Z",
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{
"id": 314931,
"topic": "gcn.circulars",
"uuid": "efc3cbf4-5eb1-42bf-9f90-bf87aee56240",
"title": "EP250526a: SVOM/VT optical upper limit",
"submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"authors": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"data": {
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},
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"bibcode": "2025GCN.40562....1X",
"eventId": "EP250526a",
"subject": "EP250526a: SVOM/VT optical upper limit",
"createdOn": 1748437143822,
"submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"circularId": 40562,
"submittedHow": "web"
},
"message_text": "L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, J. Wang, D. Y. Li (NAO, CAS), B.-T. Wang (YNAO, CAS), W. F. Wen (SZTU), J. H. Wu (GZHU), Y. Liu (NAO, CAS) report on behalf of the SVOM and EP mission team\n\nSVOM/VT conducted ToO follow-up observations of the EP250526a (Li et al., GCN 40550, Wu et al., GCN 40554). The observation started on 2025-05-27T04:04:19 UT (i.e. 7.66 hour after trigger time) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. \n\nNo uncatalogued source was detected, compared to the Legacy survey, within errorbox of EP-FXT (Li et al., GCN 40550), down to 3 sigma upper limit of VT_R~23.0 mag (AB) in 16*70 sec stacked images at the mid time of 7.81 hour.\n\nThe upper limit is consistent with the reports(Lipunov et al., GCN 40551, Angulo et al., GCN 40552).\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n\n",
"published": "2025-06-29T06:22:08.500858Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:08.500871Z",
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{
"id": 203288,
"topic": "gcn.circulars",
"uuid": "91fee868-b7ba-4865-bce9-57b9afb6f2c4",
"title": "EP250610a: COLIBRÍ optical upper limit",
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"authors": "Benjamin Schneider at MIT <bschn@mit.edu>",
"data": {
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"eventId": "EP250610a",
"subject": "EP250610a: COLIBRÍ optical upper limit",
"createdOn": 1749540427268,
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"circularId": 40661,
"submittedHow": "web"
},
"message_text": "Benjamin Schneider (LAM), Ramandeep Gill (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field of the EP250610a (Zhang et al., GCN Circ. 40660) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-06-10T05:04:33 to 05:23:35 UTC (from 38.7 to 57.8 minutes after the trigger, 3 minutes after the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn the stacked image, we do not detect any new source at the FXT position (Zhang et al., GCN Circ. 40660) down to the following 3-sigma limit:\n\ni > 22.9\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.",
"published": "2025-06-10T07:27:45.413178Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T07:27:45.413193Z",
"modified": "2025-06-10T07:27:45.421085Z",
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},
{
"id": 203287,
"topic": "gcn.circulars",
"uuid": "a715939f-4b8c-4944-acc7-1a1d85def790",
"title": "EP250610a: COLIBRÍ optical upper limit",
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"authors": "Benjamin Schneider at MIT <bschn@mit.edu>",
"data": {
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"subject": "EP250610a: COLIBRÍ optical upper limit",
"createdOn": 1749540427268,
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"circularId": 40661,
"submittedHow": "web"
},
"message_text": "Benjamin Schneider (LAM), Ramandeep Gill (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field of the EP250610a (Zhang et al., GCN Circ. 40660) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-06-10T05:04:33 to 05:23:35 UTC (from 38.7 to 57.8 minutes after the trigger, 3 minutes after the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn the stacked image, we do not detect any new source at the FXT position (Zhang et al., GCN Circ. 40660) down to the following 3-sigma limit:\n\ni > 22.9\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.",
"published": "2025-06-10T07:27:15.330595Z",
"message_parser": "GCN Circular Parser v2",
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"created": "2025-06-10T07:27:15.330608Z",
"modified": "2025-06-10T07:27:15.335533Z",
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},
{
"id": 315024,
"topic": "gcn.circulars",
"uuid": "f407e2ba-908a-4e81-ad82-1f17a3c02b9c",
"title": "EP250610a: COLIBRÍ optical upper limit",
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"authors": "Benjamin Schneider at MIT <bschn@mit.edu>",
"data": {
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"createdOn": 1749540427268,
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"circularId": 40661,
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},
"message_text": "Benjamin Schneider (LAM), Ramandeep Gill (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field of the EP250610a (Zhang et al., GCN Circ. 40660) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-06-10T05:04:33 to 05:23:35 UTC (from 38.7 to 57.8 minutes after the trigger, 3 minutes after the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn the stacked image, we do not detect any new source at the FXT position (Zhang et al., GCN Circ. 40660) down to the following 3-sigma limit:\n\ni > 22.9\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.",
"published": "2025-06-29T06:22:09.297987Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.297999Z",
"modified": "2025-06-29T06:22:09.301647Z",
"nonlocalizedevents": [],
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},
{
"id": 315025,
"topic": "gcn.circulars",
"uuid": "3959d9b9-5bee-43f7-abfa-1a0e5e4369af",
"title": "EP250610a: COLIBRÍ optical upper limit",
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"authors": "Benjamin Schneider at MIT <bschn@mit.edu>",
"data": {
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"createdOn": 1749540427268,
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"circularId": 40661,
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},
"message_text": "Benjamin Schneider (LAM), Ramandeep Gill (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field of the EP250610a (Zhang et al., GCN Circ. 40660) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-06-10T05:04:33 to 05:23:35 UTC (from 38.7 to 57.8 minutes after the trigger, 3 minutes after the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn the stacked image, we do not detect any new source at the FXT position (Zhang et al., GCN Circ. 40660) down to the following 3-sigma limit:\n\ni > 22.9\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.",
"published": "2025-06-29T06:22:09.306434Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.306446Z",
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},
{
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"topic": "gcn.circulars",
"uuid": "a78f1d59-bf90-47b1-87c4-7fc640efd5cf",
"title": "EP250610a: COLIBRÍ optical upper limit",
"submitter": "Benjamin Schneider at MIT <bschn@mit.edu>",
"authors": "Benjamin Schneider at MIT <bschn@mit.edu>",
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"submittedHow": "web"
},
"message_text": "Benjamin Schneider (LAM), Ramandeep Gill (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field of the EP250610a (Zhang et al., GCN Circ. 40660) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-06-10T05:04:33 to 05:23:35 UTC (from 38.7 to 57.8 minutes after the trigger, 3 minutes after the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn the stacked image, we do not detect any new source at the FXT position (Zhang et al., GCN Circ. 40660) down to the following 3-sigma limit:\n\ni > 22.9\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.",
"published": "2025-06-30T08:08:41.711563Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:41.711576Z",
"modified": "2025-06-30T08:08:41.714152Z",
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},
{
"id": 330230,
"topic": "gcn.circulars",
"uuid": "6ea3d8b1-247b-420a-ac08-c42c83440b0c",
"title": "EP250610a: continuous follow-up observations with EP-FXT",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40696"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40696....1C",
"eventId": "EP250610a",
"subject": "EP250610a: continuous follow-up observations with EP-FXT",
"createdOn": 1749718334655,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40696,
"submittedHow": "web"
},
"message_text": "H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) , T. Y. Lian, C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:\n\nFollowing the detection of the fast X-ray transient EP250610a (Zhang et al., GCN 40660, Lian et al. GCN 40669) and its multi-wavelength follow-up observations (Schneider et al., GCN 40661, Evans et al., GCN 40662, Brivio et al., GCN 40665, Yao et al., GCN 40666, Lipunov et al., GCN 40673, Eyles-Ferris et al., GCN 40686, Brivio et al., GCN 40688, Siegel et al., GCN 40690), we performed two target-of-opportunity (ToO) observations with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission. The X-ray counterpart detected in the autonomous follow-up observation (Lian et al. GCN 40669) as well as the Swift follow-up observation (Evans et al., GCN 40662) was detected in both epochs.\n\nThe first ToO observation began at 2025-06-10 15:36:01 (UTC), about 11 hours after the EP-WXT detection. The exposure time is 2975 seconds. Preliminary analysis shows that the 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 9.5e19 cm^-2 and a photon index of 1.97(-0.77, +0.86). The unabsorbed 0.5-10 keV flux is 1.13 (-0.53, +1.24) e-13 erg/s/cm^2 (90% C.L.), about one order of magnitude lower than that measured in the autonomous follow-up observation (Lian et al. GCN 40669).\n\nThe second ToO observation began at 2025-06-11 15:35:15 (UTC), about 35 hours after the EP-WXT detection. The exposure time is 5950 seconds. Preliminary analysis shows that the 0.5-10 keV spectrum of this epoch can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 9.5e19 cm^-2 and a photon index of 1.39(-0.94, +0.83), yielding an unabsorbed 0.5-10 keV flux of 6.91(-4.42, +14.50)e-14 erg/s/cm^2 (90% C.L.). The uncertainties are given at 90 percent confidence level for all the above parameters.\n\nEP-FXT will continue monitoring the source in the forthcoming days. Multi-band follow-up observations are encouraged. The contact TAs of EP250610a are Tianying Lian and Huaqing Cheng, please contact them via the email tylian@nao.cas.cn and hqcheng@nao.cas.cn if needed.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-30T08:08:51.171222Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:51.171235Z",
"modified": "2025-06-30T08:08:51.173796Z",
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},
{
"id": 208244,
"topic": "gcn.circulars",
"uuid": "dcb6f1d3-2aeb-455f-85de-ec55de636697",
"title": "EP250610a: continuous follow-up observations with EP-FXT",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40696"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: continuous follow-up observations with EP-FXT",
"createdOn": 1749718334655,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40696,
"submittedHow": "web"
},
"message_text": "H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) , T. Y. Lian, C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:\n\nFollowing the detection of the fast X-ray transient EP250610a (Zhang et al., GCN 40660, Lian et al. GCN 40669) and its multi-wavelength follow-up observations (Schneider et al., GCN 40661, Evans et al., GCN 40662, Brivio et al., GCN 40665, Yao et al., GCN 40666, Lipunov et al., GCN 40673, Eyles-Ferris et al., GCN 40686, Brivio et al., GCN 40688, Siegel et al., GCN 40690), we performed two target-of-opportunity (ToO) observations with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission. The X-ray counterpart detected in the autonomous follow-up observation (Lian et al. GCN 40669) as well as the Swift follow-up observation (Evans et al., GCN 40662) was detected in both epochs.\n\nThe first ToO observation began at 2025-06-10 15:36:01 (UTC), about 11 hours after the EP-WXT detection. The exposure time is 2975 seconds. Preliminary analysis shows that the 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 9.5e19 cm^-2 and a photon index of 1.97(-0.77, +0.86). The unabsorbed 0.5-10 keV flux is 1.13 (-0.53, +1.24) e-13 erg/s/cm^2 (90% C.L.), about one order of magnitude lower than that measured in the autonomous follow-up observation (Lian et al. GCN 40669).\n\nThe second ToO observation began at 2025-06-11 15:35:15 (UTC), about 35 hours after the EP-WXT detection. The exposure time is 5950 seconds. Preliminary analysis shows that the 0.5-10 keV spectrum of this epoch can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 9.5e19 cm^-2 and a photon index of 1.39(-0.94, +0.83), yielding an unabsorbed 0.5-10 keV flux of 6.91(-4.42, +14.50)e-14 erg/s/cm^2 (90% C.L.). The uncertainties are given at 90 percent confidence level for all the above parameters.\n\nEP-FXT will continue monitoring the source in the forthcoming days. Multi-band follow-up observations are encouraged. The contact TAs of EP250610a are Tianying Lian and Huaqing Cheng, please contact them via the email tylian@nao.cas.cn and hqcheng@nao.cas.cn if needed.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-12T08:52:23.094784Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-12T08:52:23.094798Z",
"modified": "2025-06-12T08:52:23.112006Z",
"nonlocalizedevents": [],
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},
{
"id": 315065,
"topic": "gcn.circulars",
"uuid": "9fc19d63-833b-4906-be98-483a60bf8544",
"title": "EP250610a: continuous follow-up observations with EP-FXT",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40696"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: continuous follow-up observations with EP-FXT",
"createdOn": 1749718334655,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40696,
"submittedHow": "web"
},
"message_text": "H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) , T. Y. Lian, C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:\n\nFollowing the detection of the fast X-ray transient EP250610a (Zhang et al., GCN 40660, Lian et al. GCN 40669) and its multi-wavelength follow-up observations (Schneider et al., GCN 40661, Evans et al., GCN 40662, Brivio et al., GCN 40665, Yao et al., GCN 40666, Lipunov et al., GCN 40673, Eyles-Ferris et al., GCN 40686, Brivio et al., GCN 40688, Siegel et al., GCN 40690), we performed two target-of-opportunity (ToO) observations with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission. The X-ray counterpart detected in the autonomous follow-up observation (Lian et al. GCN 40669) as well as the Swift follow-up observation (Evans et al., GCN 40662) was detected in both epochs.\n\nThe first ToO observation began at 2025-06-10 15:36:01 (UTC), about 11 hours after the EP-WXT detection. The exposure time is 2975 seconds. Preliminary analysis shows that the 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 9.5e19 cm^-2 and a photon index of 1.97(-0.77, +0.86). The unabsorbed 0.5-10 keV flux is 1.13 (-0.53, +1.24) e-13 erg/s/cm^2 (90% C.L.), about one order of magnitude lower than that measured in the autonomous follow-up observation (Lian et al. GCN 40669).\n\nThe second ToO observation began at 2025-06-11 15:35:15 (UTC), about 35 hours after the EP-WXT detection. The exposure time is 5950 seconds. Preliminary analysis shows that the 0.5-10 keV spectrum of this epoch can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 9.5e19 cm^-2 and a photon index of 1.39(-0.94, +0.83), yielding an unabsorbed 0.5-10 keV flux of 6.91(-4.42, +14.50)e-14 erg/s/cm^2 (90% C.L.). The uncertainties are given at 90 percent confidence level for all the above parameters.\n\nEP-FXT will continue monitoring the source in the forthcoming days. Multi-band follow-up observations are encouraged. The contact TAs of EP250610a are Tianying Lian and Huaqing Cheng, please contact them via the email tylian@nao.cas.cn and hqcheng@nao.cas.cn if needed.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-29T06:22:09.687872Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.687884Z",
"modified": "2025-06-29T06:22:09.690971Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315023,
"topic": "gcn.circulars",
"uuid": "ac6d4a45-dde1-4f0f-844a-2508419786ec",
"title": "EP250610a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40660"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Einstein Probe detection of an X-ray transient",
"createdOn": 1749537633275,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40660,
"submittedHow": "web"
},
"message_text": "Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250610a. The transient triggered EP-WXT (ID: 01709178308) at 2025-06-10T04:25:50 (UTC). The WXT position of the source is R.A. = 248.310 deg, DEC = 38.527 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 248.3573 deg, DEC = 38.5387 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nFurther information will be updated when the telemetry data is received.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n",
"published": "2025-06-29T06:22:09.288587Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.288599Z",
"modified": "2025-06-29T06:22:09.291497Z",
"nonlocalizedevents": [],
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},
{
"id": 203281,
"topic": "gcn.circulars",
"uuid": "72ebc566-b614-481b-88fb-4e4bc4dba1f6",
"title": "EP250610a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40660"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Einstein Probe detection of an X-ray transient",
"createdOn": 1749537633275,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40660,
"submittedHow": "web"
},
"message_text": "Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250610a. The transient triggered EP-WXT (ID: 01709178308) at 2025-06-10T04:25:50 (UTC). The WXT position of the source is R.A. = 248.310 deg, DEC = 38.527 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 248.3573 deg, DEC = 38.5387 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nFurther information will be updated when the telemetry data is received.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n",
"published": "2025-06-10T06:40:42.467344Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T06:40:42.467357Z",
"modified": "2025-06-10T06:40:42.485801Z",
"nonlocalizedevents": [],
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},
{
"id": 330199,
"topic": "gcn.circulars",
"uuid": "44456801-a34b-4734-b3e6-17b07893fbe1",
"title": "EP250610a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40660"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40660....1Z",
"eventId": "EP250610a",
"subject": "EP250610a: Einstein Probe detection of an X-ray transient",
"createdOn": 1749537633275,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40660,
"submittedHow": "web"
},
"message_text": "Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250610a. The transient triggered EP-WXT (ID: 01709178308) at 2025-06-10T04:25:50 (UTC). The WXT position of the source is R.A. = 248.310 deg, DEC = 38.527 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 248.3573 deg, DEC = 38.5387 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nFurther information will be updated when the telemetry data is received.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n",
"published": "2025-06-30T08:08:45.943221Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:45.943233Z",
"modified": "2025-06-30T08:08:45.945681Z",
"nonlocalizedevents": [],
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},
{
"id": 203493,
"topic": "gcn.circulars",
"uuid": "defaa609-02ee-4dda-8425-31296821b7d4",
"title": "EP250610a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40673"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Global MASTER-Net observations report",
"createdOn": 1749584180804,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40673,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250610a ( EP Team et al., GCN 40660) errorbox 972 sec after notice time and 9094 sec after trigger time at 2025-06-10 06:57:24 UT, with upper limit up to 17.6 mag. The observations began at zenith distance = 82 deg. The sun altitude is -57.2 deg. \n\nMASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250610a errorbox 44872 sec after notice time and 52993 sec after trigger time at 2025-06-10 19:09:03 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 15 deg. The sun altitude is -18.3 deg. \n\nThe galactic latitude b = 42 deg., longitude l = 61 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2898181\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 9229 | 2025-06-10 06:57:24 | MASTER-OAFA | (16h 33m 32.66s , +38d 48m 08.6s) | C | 270 | 17.6 | Coadd \n 53024 | 2025-06-10 19:09:03 | MASTER-Kislovodsk | (16h 31m 32.68s , +38d 50m 44.6s) | C | 60 | 17.0 | \n 53210 | 2025-06-10 19:12:09 | MASTER-Kislovodsk | (16h 31m 34.53s , +38d 48m 49.2s) | C | 60 | 17.4 | \n 53547 | 2025-06-10 19:17:46 | MASTER-Kislovodsk | (16h 31m 41.01s , +38d 50m 51.7s) | C | 60 | 17.1 | \n 53720 | 2025-06-10 19:20:40 | MASTER-Kislovodsk | (16h 31m 35.46s , +38d 50m 56.6s) | C | 60 | 16.0 | \n 53893 | 2025-06-10 19:23:32 | MASTER-Kislovodsk | (16h 31m 32.13s , +38d 48m 59.5s) | C | 60 | 17.0 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-06-10T19:36:29.698194Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T19:36:29.698215Z",
"modified": "2025-06-10T19:36:29.729308Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330185,
"topic": "gcn.circulars",
"uuid": "76b87ff3-5a6e-4ce3-9fd5-d20c9deaa1e8",
"title": "EP250610a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40673"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40673....1L",
"eventId": "EP250610a",
"subject": "EP250610a: Global MASTER-Net observations report",
"createdOn": 1749584180804,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40673,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250610a ( EP Team et al., GCN 40660) errorbox 972 sec after notice time and 9094 sec after trigger time at 2025-06-10 06:57:24 UT, with upper limit up to 17.6 mag. The observations began at zenith distance = 82 deg. The sun altitude is -57.2 deg. \n\nMASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250610a errorbox 44872 sec after notice time and 52993 sec after trigger time at 2025-06-10 19:09:03 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 15 deg. The sun altitude is -18.3 deg. \n\nThe galactic latitude b = 42 deg., longitude l = 61 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2898181\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 9229 | 2025-06-10 06:57:24 | MASTER-OAFA | (16h 33m 32.66s , +38d 48m 08.6s) | C | 270 | 17.6 | Coadd \n 53024 | 2025-06-10 19:09:03 | MASTER-Kislovodsk | (16h 31m 32.68s , +38d 50m 44.6s) | C | 60 | 17.0 | \n 53210 | 2025-06-10 19:12:09 | MASTER-Kislovodsk | (16h 31m 34.53s , +38d 48m 49.2s) | C | 60 | 17.4 | \n 53547 | 2025-06-10 19:17:46 | MASTER-Kislovodsk | (16h 31m 41.01s , +38d 50m 51.7s) | C | 60 | 17.1 | \n 53720 | 2025-06-10 19:20:40 | MASTER-Kislovodsk | (16h 31m 35.46s , +38d 50m 56.6s) | C | 60 | 16.0 | \n 53893 | 2025-06-10 19:23:32 | MASTER-Kislovodsk | (16h 31m 32.13s , +38d 48m 59.5s) | C | 60 | 17.0 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-06-30T08:08:45.849989Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:45.850002Z",
"modified": "2025-06-30T08:08:45.852553Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315040,
"topic": "gcn.circulars",
"uuid": "cfd82aa0-3a53-4ef0-93f1-af3bab7b7951",
"title": "EP250610a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40673"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Global MASTER-Net observations report",
"createdOn": 1749584180804,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40673,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250610a ( EP Team et al., GCN 40660) errorbox 972 sec after notice time and 9094 sec after trigger time at 2025-06-10 06:57:24 UT, with upper limit up to 17.6 mag. The observations began at zenith distance = 82 deg. The sun altitude is -57.2 deg. \n\nMASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250610a errorbox 44872 sec after notice time and 52993 sec after trigger time at 2025-06-10 19:09:03 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 15 deg. The sun altitude is -18.3 deg. \n\nThe galactic latitude b = 42 deg., longitude l = 61 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2898181\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 9229 | 2025-06-10 06:57:24 | MASTER-OAFA | (16h 33m 32.66s , +38d 48m 08.6s) | C | 270 | 17.6 | Coadd \n 53024 | 2025-06-10 19:09:03 | MASTER-Kislovodsk | (16h 31m 32.68s , +38d 50m 44.6s) | C | 60 | 17.0 | \n 53210 | 2025-06-10 19:12:09 | MASTER-Kislovodsk | (16h 31m 34.53s , +38d 48m 49.2s) | C | 60 | 17.4 | \n 53547 | 2025-06-10 19:17:46 | MASTER-Kislovodsk | (16h 31m 41.01s , +38d 50m 51.7s) | C | 60 | 17.1 | \n 53720 | 2025-06-10 19:20:40 | MASTER-Kislovodsk | (16h 31m 35.46s , +38d 50m 56.6s) | C | 60 | 16.0 | \n 53893 | 2025-06-10 19:23:32 | MASTER-Kislovodsk | (16h 31m 32.13s , +38d 48m 59.5s) | C | 60 | 17.0 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-06-29T06:22:09.478177Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.478189Z",
"modified": "2025-06-29T06:22:09.480945Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330305,
"topic": "gcn.circulars",
"uuid": "8cc7ea07-d9be-4a37-9c6b-3cbe08dae97d",
"title": "EP250610a: Liverpool Telescope optical upper limits",
"submitter": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"authors": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40686"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40686....1E",
"eventId": "EP250610a",
"subject": "EP250610a: Liverpool Telescope optical upper limits",
"createdOn": 1749636811370,
"submitter": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"circularId": 40686,
"submittedHow": "web"
},
"message_text": "R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report:\n\nWe observed the field of the X-ray transient EP250610a (Zhang et al., GCN 40660; Lian et al., GCN 40669) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2025-05-11 00:16:50 UT, approximately 19.9 hours after the X-ray detection.\n\nWe performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. In agreement with Schneider et al. (GCN 40661), Brivio et al. (GCN 40665), Yao et al. (GCN 40666) and Lipunov et al. (GCN 40673), we identify no new sources within the positional uncertainty of the X-ray source identified by Evans et al. (GCN 40662) and Lian et al. (GCN 40669).\n\nAt the position of the X-ray source, we derive 3-sigma upper limits of r’ > 22.1 and g’ > 22.1 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction.",
"published": "2025-06-30T08:09:37.087424Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:09:37.087437Z",
"modified": "2025-06-30T08:09:37.092221Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315053,
"topic": "gcn.circulars",
"uuid": "bae0f90a-d1ea-4fe7-ba14-ec4f995efecc",
"title": "EP250610a: Liverpool Telescope optical upper limits",
"submitter": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"authors": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40686"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Liverpool Telescope optical upper limits",
"createdOn": 1749636811370,
"submitter": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"circularId": 40686,
"submittedHow": "web"
},
"message_text": "R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report:\n\nWe observed the field of the X-ray transient EP250610a (Zhang et al., GCN 40660; Lian et al., GCN 40669) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2025-05-11 00:16:50 UT, approximately 19.9 hours after the X-ray detection.\n\nWe performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. In agreement with Schneider et al. (GCN 40661), Brivio et al. (GCN 40665), Yao et al. (GCN 40666) and Lipunov et al. (GCN 40673), we identify no new sources within the positional uncertainty of the X-ray source identified by Evans et al. (GCN 40662) and Lian et al. (GCN 40669).\n\nAt the position of the X-ray source, we derive 3-sigma upper limits of r’ > 22.1 and g’ > 22.1 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction.",
"published": "2025-06-29T06:22:09.589714Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.589726Z",
"modified": "2025-06-29T06:22:09.592586Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203718,
"topic": "gcn.circulars",
"uuid": "c788e3de-1cbf-4e4d-b0f3-369c167727a1",
"title": "EP250610a: Liverpool Telescope optical upper limits",
"submitter": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"authors": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40686"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Liverpool Telescope optical upper limits",
"createdOn": 1749636811370,
"submitter": "Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>",
"circularId": 40686,
"submittedHow": "web"
},
"message_text": "R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report:\n\nWe observed the field of the X-ray transient EP250610a (Zhang et al., GCN 40660; Lian et al., GCN 40669) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2025-05-11 00:16:50 UT, approximately 19.9 hours after the X-ray detection.\n\nWe performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. In agreement with Schneider et al. (GCN 40661), Brivio et al. (GCN 40665), Yao et al. (GCN 40666) and Lipunov et al. (GCN 40673), we identify no new sources within the positional uncertainty of the X-ray source identified by Evans et al. (GCN 40662) and Lian et al. (GCN 40669).\n\nAt the position of the X-ray source, we derive 3-sigma upper limits of r’ > 22.1 and g’ > 22.1 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction.",
"published": "2025-06-11T10:13:39.701436Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-11T10:13:39.701456Z",
"modified": "2025-06-11T10:13:39.719819Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203374,
"topic": "gcn.circulars",
"uuid": "2db66e24-ab1b-480c-b3a8-a20afeba1def",
"title": "EP250610a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40669"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1749565004023,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40669,
"submittedHow": "web"
},
"message_text": "T.Y. Lian, H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:\n\nThe fast X-ray transient EP250610a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 40660), and followed up by several optical and X-ray telescopes (Schneider et al., GCN 40661, Brivio et al., GCN 40665, Evans et al., GCN 40662). Refined analysis of the WXT data shows that the event started at T0=2025-06-10T04:23:24 (UTC) and lasted for about 140s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 2.2 x 10^-9 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 0.7 (-/+0.8). The derived average unabsorbed 0.5-4 keV flux is 5.2 (-2.3, +4.2) x 10^-10 erg/s/cm^2. \n\nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-10T04:26:32, about 3 minutes after T0, with an exposure time of 3946 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 248.3567, DEC = 38.5362 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Swift/XRT (Source 1 in Evans et al., GCN 40662). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 2.34 (-0.12, +0.12). The derived unabsorbed 0.5-10 keV flux is 1.87 (-0.17, +0.19) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n\nThe contact TAs of this source are Tianying Lian and Huaqing Cheng, please contact them via the email tylian@nao.cas.cn and hqcheng@nao.cas.cn if needed.",
"published": "2025-06-10T14:16:53.157850Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T14:16:53.157871Z",
"modified": "2025-06-10T14:16:53.204248Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315033,
"topic": "gcn.circulars",
"uuid": "fab6cefe-29bd-43a1-a301-e46636b94fdc",
"title": "EP250610a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40669"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1749565004023,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40669,
"submittedHow": "web"
},
"message_text": "T.Y. Lian, H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:\n\nThe fast X-ray transient EP250610a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 40660), and followed up by several optical and X-ray telescopes (Schneider et al., GCN 40661, Brivio et al., GCN 40665, Evans et al., GCN 40662). Refined analysis of the WXT data shows that the event started at T0=2025-06-10T04:23:24 (UTC) and lasted for about 140s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 2.2 x 10^-9 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 0.7 (-/+0.8). The derived average unabsorbed 0.5-4 keV flux is 5.2 (-2.3, +4.2) x 10^-10 erg/s/cm^2. \n\nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-10T04:26:32, about 3 minutes after T0, with an exposure time of 3946 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 248.3567, DEC = 38.5362 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Swift/XRT (Source 1 in Evans et al., GCN 40662). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 2.34 (-0.12, +0.12). The derived unabsorbed 0.5-10 keV flux is 1.87 (-0.17, +0.19) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n\nThe contact TAs of this source are Tianying Lian and Huaqing Cheng, please contact them via the email tylian@nao.cas.cn and hqcheng@nao.cas.cn if needed.",
"published": "2025-06-29T06:22:09.376911Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.376923Z",
"modified": "2025-06-29T06:22:09.382937Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330284,
"topic": "gcn.circulars",
"uuid": "f0d5bf99-fccd-40b4-9ad2-d39775707814",
"title": "EP250610a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40669"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40669....1L",
"eventId": "EP250610a",
"subject": "EP250610a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1749565004023,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40669,
"submittedHow": "web"
},
"message_text": "T.Y. Lian, H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:\n\nThe fast X-ray transient EP250610a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 40660), and followed up by several optical and X-ray telescopes (Schneider et al., GCN 40661, Brivio et al., GCN 40665, Evans et al., GCN 40662). Refined analysis of the WXT data shows that the event started at T0=2025-06-10T04:23:24 (UTC) and lasted for about 140s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 2.2 x 10^-9 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 0.7 (-/+0.8). The derived average unabsorbed 0.5-4 keV flux is 5.2 (-2.3, +4.2) x 10^-10 erg/s/cm^2. \n\nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-10T04:26:32, about 3 minutes after T0, with an exposure time of 3946 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 248.3567, DEC = 38.5362 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Swift/XRT (Source 1 in Evans et al., GCN 40662). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 2.34 (-0.12, +0.12). The derived unabsorbed 0.5-10 keV flux is 1.87 (-0.17, +0.19) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n\nThe contact TAs of this source are Tianying Lian and Huaqing Cheng, please contact them via the email tylian@nao.cas.cn and hqcheng@nao.cas.cn if needed.",
"published": "2025-06-30T08:09:07.563778Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:09:07.563791Z",
"modified": "2025-06-30T08:09:07.566311Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315029,
"topic": "gcn.circulars",
"uuid": "a3f4139f-0f0c-4915-bb4e-96c4e616be7b",
"title": "EP250610a: REM optical/NIR observations",
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"authors": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40665"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: REM optical/NIR observations",
"createdOn": 1749558035710,
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"circularId": 40665,
"submittedHow": "web"
},
"message_text": "R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:\n\nWe observed the field of EP 250610a detected by EP/WXT (Zhang et al., GCN 40660) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, and H bands, started on 2025 June 10 at 05:02:09 UT (i.e. 36 min after the burst), and lasted for about 1 hour.\n\nFrom preliminary inspection, we do not detect any possible counterpart at the position of the candidate detected by Swift/XRT (source 1, Evans et al., GCN 40662) down to the following 3sigma limits:\n\nr > 18.7 (AB; calibrated against the Pan-STARRS catalogue),\nat a mid-time of 66 min after the trigger;\n\nH > 16.6 (Vega; calibrated against the 2MASS catalogue),\nat a mid-time of 39 min after the trigger.",
"published": "2025-06-29T06:22:09.340859Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.340871Z",
"modified": "2025-06-29T06:22:09.343760Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203342,
"topic": "gcn.circulars",
"uuid": "e40e1603-13d9-44f6-9c28-4dc58fa47000",
"title": "EP250610a: REM optical/NIR observations",
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"authors": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40665"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: REM optical/NIR observations",
"createdOn": 1749558035710,
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"circularId": 40665,
"submittedHow": "web"
},
"message_text": "R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:\n\nWe observed the field of EP 250610a detected by EP/WXT (Zhang et al., GCN 40660) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, and H bands, started on 2025 June 10 at 05:02:09 UT (i.e. 36 min after the burst), and lasted for about 1 hour.\n\nFrom preliminary inspection, we do not detect any possible counterpart at the position of the candidate detected by Swift/XRT (source 1, Evans et al., GCN 40662) down to the following 3sigma limits:\n\nr > 18.7 (AB; calibrated against the Pan-STARRS catalogue),\nat a mid-time of 66 min after the trigger;\n\nH > 16.6 (Vega; calibrated against the 2MASS catalogue),\nat a mid-time of 39 min after the trigger.",
"published": "2025-06-10T12:20:44.938163Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T12:20:44.938182Z",
"modified": "2025-06-10T12:20:44.998001Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330200,
"topic": "gcn.circulars",
"uuid": "3cd3fa27-b538-43ea-bc38-ee1d1bb615b9",
"title": "EP250610a: REM optical/NIR observations",
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"authors": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40665"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40665....1B",
"eventId": "EP250610a",
"subject": "EP250610a: REM optical/NIR observations",
"createdOn": 1749558035710,
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"circularId": 40665,
"submittedHow": "web"
},
"message_text": "R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:\n\nWe observed the field of EP 250610a detected by EP/WXT (Zhang et al., GCN 40660) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, and H bands, started on 2025 June 10 at 05:02:09 UT (i.e. 36 min after the burst), and lasted for about 1 hour.\n\nFrom preliminary inspection, we do not detect any possible counterpart at the position of the candidate detected by Swift/XRT (source 1, Evans et al., GCN 40662) down to the following 3sigma limits:\n\nr > 18.7 (AB; calibrated against the Pan-STARRS catalogue),\nat a mid-time of 66 min after the trigger;\n\nH > 16.6 (Vega; calibrated against the 2MASS catalogue),\nat a mid-time of 39 min after the trigger.",
"published": "2025-06-30T08:08:45.949498Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:45.949511Z",
"modified": "2025-06-30T08:08:45.952232Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203348,
"topic": "gcn.circulars",
"uuid": "c1110533-e290-4638-8d9e-0cf612ca67cd",
"title": "EP250610a: SVOM/VT optical upper limit",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40666"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: SVOM/VT optical upper limit",
"createdOn": 1749560124429,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 40666,
"submittedHow": "web"
},
"message_text": "Z. H. Yao, L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA),Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS), Lin Lan (NAOC), Run-Chao Chen (NJU), Chen-Wei Wang, Wen-Jun Tan (IHEP) report on behalf of the SVOM and EP mission team:\n\nSVOM performed a Target of Opportunity observation of EP250610a detected by EP/WXT (Zhang et al., GCN 40660). SVOM/VT began observing the field at 2025-06-10 06:16:38 UTC, 1.85 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.\n\nNo credible candidate was detected in our single or stacked images within the errorbox of EP/FXT (Zhang et al., GCN 40660) or Swift/XRT (Evans et al., GCN 40662 ), the three sigma limits are:\n \n[date-obs|mid-time] | exposure time (s) | band | upper limit (AB) \n----------- --------|-------------------|------|-----------------\n2025-06-10T07:29:10 | 76×70 | VT_B | 23.93\n2025-06-10T07:29:10 | 76×70 | VT_R | 23.45\n\nThe upper limit is consistent with reports (Schneider et al., GCN 40661, Brivio et al., GCN 40665).\n \nDeeper or redder follow-ups are encouraged to investigate the nature of the transient。\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n",
"published": "2025-06-10T12:55:31.616562Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T12:55:31.616582Z",
"modified": "2025-06-10T12:55:31.637915Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330244,
"topic": "gcn.circulars",
"uuid": "eafd98af-9df6-4a59-9bd9-3657dddafd0b",
"title": "EP250610a: SVOM/VT optical upper limit",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40666"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40666....1Y",
"eventId": "EP250610a",
"subject": "EP250610a: SVOM/VT optical upper limit",
"createdOn": 1749560124429,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 40666,
"submittedHow": "web"
},
"message_text": "Z. H. Yao, L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA),Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS), Lin Lan (NAOC), Run-Chao Chen (NJU), Chen-Wei Wang, Wen-Jun Tan (IHEP) report on behalf of the SVOM and EP mission team:\n\nSVOM performed a Target of Opportunity observation of EP250610a detected by EP/WXT (Zhang et al., GCN 40660). SVOM/VT began observing the field at 2025-06-10 06:16:38 UTC, 1.85 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.\n\nNo credible candidate was detected in our single or stacked images within the errorbox of EP/FXT (Zhang et al., GCN 40660) or Swift/XRT (Evans et al., GCN 40662 ), the three sigma limits are:\n \n[date-obs|mid-time] | exposure time (s) | band | upper limit (AB) \n----------- --------|-------------------|------|-----------------\n2025-06-10T07:29:10 | 76×70 | VT_B | 23.93\n2025-06-10T07:29:10 | 76×70 | VT_R | 23.45\n\nThe upper limit is consistent with reports (Schneider et al., GCN 40661, Brivio et al., GCN 40665).\n \nDeeper or redder follow-ups are encouraged to investigate the nature of the transient。\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n",
"published": "2025-06-30T08:08:52.267564Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:52.267577Z",
"modified": "2025-06-30T08:08:52.270174Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315030,
"topic": "gcn.circulars",
"uuid": "b686bf53-6421-4915-b273-fedda0ba32b4",
"title": "EP250610a: SVOM/VT optical upper limit",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40666"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: SVOM/VT optical upper limit",
"createdOn": 1749560124429,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 40666,
"submittedHow": "web"
},
"message_text": "Z. H. Yao, L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA),Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS), Lin Lan (NAOC), Run-Chao Chen (NJU), Chen-Wei Wang, Wen-Jun Tan (IHEP) report on behalf of the SVOM and EP mission team:\n\nSVOM performed a Target of Opportunity observation of EP250610a detected by EP/WXT (Zhang et al., GCN 40660). SVOM/VT began observing the field at 2025-06-10 06:16:38 UTC, 1.85 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.\n\nNo credible candidate was detected in our single or stacked images within the errorbox of EP/FXT (Zhang et al., GCN 40660) or Swift/XRT (Evans et al., GCN 40662 ), the three sigma limits are:\n \n[date-obs|mid-time] | exposure time (s) | band | upper limit (AB) \n----------- --------|-------------------|------|-----------------\n2025-06-10T07:29:10 | 76×70 | VT_B | 23.93\n2025-06-10T07:29:10 | 76×70 | VT_R | 23.45\n\nThe upper limit is consistent with reports (Schneider et al., GCN 40661, Brivio et al., GCN 40665).\n \nDeeper or redder follow-ups are encouraged to investigate the nature of the transient。\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n",
"published": "2025-06-29T06:22:09.348280Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.348292Z",
"modified": "2025-06-29T06:22:09.353370Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330227,
"topic": "gcn.circulars",
"uuid": "95680c83-b645-44f5-bb60-57ca65fd9567",
"title": "EP250610A: Swift/UVOT Upper limits",
"submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"authors": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40690"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40690....1S",
"eventId": "EP250610a",
"subject": "EP250610A: Swift/UVOT Upper limits",
"createdOn": 1749652787611,
"submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"circularId": 40690,
"submittedHow": "web"
},
"message_text": "M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of EP250610A 3 ks after the EP trigger (Zhang et al., GCN Circ. 40660). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40662) is seen in the initial UVOT exposures.\n\nPreliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: \n\nFilter T_start(s) T_stop(s) Exp(s) Mag\nu 3087 9399 2103 >21.44\nu 35617 41300 1846 >21.33\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.01 in the direction of the burst\n(Schlegel et al. 1998).\n",
"published": "2025-06-30T08:08:51.150633Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:51.150645Z",
"modified": "2025-06-30T08:08:51.153249Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203773,
"topic": "gcn.circulars",
"uuid": "ab97a031-0a52-449f-a89d-6ba90e8e84d8",
"title": "EP250610A: Swift/UVOT Upper limits",
"submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"authors": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40690"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610A: Swift/UVOT Upper limits",
"createdOn": 1749652787611,
"submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"circularId": 40690,
"submittedHow": "web"
},
"message_text": "M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of EP250610A 3 ks after the EP trigger (Zhang et al., GCN Circ. 40660). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40662) is seen in the initial UVOT exposures.\n\nPreliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: \n\nFilter T_start(s) T_stop(s) Exp(s) Mag\nu 3087 9399 2103 >21.44\nu 35617 41300 1846 >21.33\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.01 in the direction of the burst\n(Schlegel et al. 1998).\n",
"published": "2025-06-11T14:39:49.831672Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-11T14:39:49.831701Z",
"modified": "2025-06-11T14:39:49.954988Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315059,
"topic": "gcn.circulars",
"uuid": "3eacff6f-7ba6-44ab-9249-4c124bb3e89c",
"title": "EP250610A: Swift/UVOT Upper limits",
"submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"authors": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40690"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610A: Swift/UVOT Upper limits",
"createdOn": 1749652787611,
"submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
"circularId": 40690,
"submittedHow": "web"
},
"message_text": "M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of EP250610A 3 ks after the EP trigger (Zhang et al., GCN Circ. 40660). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40662) is seen in the initial UVOT exposures.\n\nPreliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: \n\nFilter T_start(s) T_stop(s) Exp(s) Mag\nu 3087 9399 2103 >21.44\nu 35617 41300 1846 >21.33\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.01 in the direction of the burst\n(Schlegel et al. 1998).\n",
"published": "2025-06-29T06:22:09.639082Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.639094Z",
"modified": "2025-06-29T06:22:09.642002Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315026,
"topic": "gcn.circulars",
"uuid": "cde1fbd7-18d8-4fd4-b470-2cc87078366e",
"title": "EP250610a: Swift-XRT counterpart detection",
"submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"authors": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40662"
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"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Swift-XRT counterpart detection",
"createdOn": 1749545722912,
"submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"circularId": 40662,
"submittedHow": "email"
},
"message_text": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P.\nBeardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.\nBurrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),\nP. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro\n(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato\n(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected\nsource EP250610a, collecting 2.1 ks of Photon Counting (PC) mode data between T0+2.8\nks and T0+9.4 ks after the trigger. A candidate counterpart has been found. The\ndetails of this source are:\n\n Source 1 (SWIFT J163325.5+383159):\n ==================================\n RA (J2000.0): 248.3564 =\t16h 33m 25.54s\n Dec (J2000.0): +38.5332 =\t+38d 31' 59.5\"\n Error:\t 4.6 (arcsec, radius, 90% confidence).\n Detect flag: GOOD\n Distance:\t 2.2 arcmin from the Einstein Probe/WXT position.\n Mean rate:\t 0.0111 +/- 0.0027 ct s^-1\n Mean flux:\t (4.4 +/- 1.1)e-13 erg cm^-2 s^-1\n Peak rate:\t 0.0111 +/- 0.0027 ct s^-1\n Peak flux:\t (4.4 +/- 1.1)e-13 erg cm^-2 s^-1\n ECF:\t 3.96e-11 erg cm^-2 ct^-1, assuming NH=1.07e+20 cm^-2,\n\t\t gamma=1.73; determined from a spectral fit.\n LSXPS UL:\t 2.4e-03 ct/sec, (0.3-10 keV)\n\t so the source is 3.1-sigma above this 3-sigma upper limit.\n There is no evidence for fading.\n\n\nWe have detected a total of 2 sources. These have been automatically classified as\nfollows:\n * 0 likely counterparts\n * 1 candidate counterpart\n * 1 uncatalogued X-ray source\n * 0 known X-ray sources\n\nUncatalogued X-ray sources\n--------------------------\n\n Source 2 (SWIFT J163309.1+383226):\n ==================================\n RA (J2000.0): 248.2883 =\t16h 33m 09.19s\n Dec (J2000.0): +38.5406 =\t+38d 32' 26.2\"\n Error:\t 7.1 (arcsec, radius, 90% confidence).\n Detect flag: REASONABLE\n Distance:\t 78 arcsec from the Einstein Probe/WXT position.\n Mean rate:\t (2.4 [+1.6, -1.1])e-3 ct s^-1\n Mean flux:\t (1.02 [+0.70, -0.49])e-13 erg cm^-2 s^-1\n Peak rate:\t (2.4 [+1.6, -1.1])e-3 ct s^-1\n Peak flux:\t (1.02 [+0.70, -0.49])e-13 erg cm^-2 s^-1\n LSXPS UL:\t 3.1e-03 ct/sec, (0.3-10 keV)\n\t so the source is not above this 3-sigma upper limit.\n There is no evidence for fading.\n There is 1 2MASS object within the source's 3-sigma error radius.\n\nAll fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with\ncatalogues and upper limits from other missions, we assumed a power-law spectrum\nwith NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.\n\nThe results of the XRT-team automatic analysis of the XRT observations, including a\nposition-specific upper limit calculator, are available at\nhttps://www.swift.ac.uk/EP.\n\nThis circular is an officicial product of the Swift-XRT team.\n\n\n",
"published": "2025-06-29T06:22:09.314509Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.314521Z",
"modified": "2025-06-29T06:22:09.317533Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203306,
"topic": "gcn.circulars",
"uuid": "ed58df23-b2f2-474d-abee-7be1e3a3daee",
"title": "EP250610a: Swift-XRT counterpart detection",
"submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"authors": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40662"
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"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: Swift-XRT counterpart detection",
"createdOn": 1749545722912,
"submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"circularId": 40662,
"submittedHow": "email"
},
"message_text": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P.\nBeardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.\nBurrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),\nP. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro\n(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato\n(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected\nsource EP250610a, collecting 2.1 ks of Photon Counting (PC) mode data between T0+2.8\nks and T0+9.4 ks after the trigger. A candidate counterpart has been found. The\ndetails of this source are:\n\n Source 1 (SWIFT J163325.5+383159):\n ==================================\n RA (J2000.0): 248.3564 =\t16h 33m 25.54s\n Dec (J2000.0): +38.5332 =\t+38d 31' 59.5\"\n Error:\t 4.6 (arcsec, radius, 90% confidence).\n Detect flag: GOOD\n Distance:\t 2.2 arcmin from the Einstein Probe/WXT position.\n Mean rate:\t 0.0111 +/- 0.0027 ct s^-1\n Mean flux:\t (4.4 +/- 1.1)e-13 erg cm^-2 s^-1\n Peak rate:\t 0.0111 +/- 0.0027 ct s^-1\n Peak flux:\t (4.4 +/- 1.1)e-13 erg cm^-2 s^-1\n ECF:\t 3.96e-11 erg cm^-2 ct^-1, assuming NH=1.07e+20 cm^-2,\n\t\t gamma=1.73; determined from a spectral fit.\n LSXPS UL:\t 2.4e-03 ct/sec, (0.3-10 keV)\n\t so the source is 3.1-sigma above this 3-sigma upper limit.\n There is no evidence for fading.\n\n\nWe have detected a total of 2 sources. These have been automatically classified as\nfollows:\n * 0 likely counterparts\n * 1 candidate counterpart\n * 1 uncatalogued X-ray source\n * 0 known X-ray sources\n\nUncatalogued X-ray sources\n--------------------------\n\n Source 2 (SWIFT J163309.1+383226):\n ==================================\n RA (J2000.0): 248.2883 =\t16h 33m 09.19s\n Dec (J2000.0): +38.5406 =\t+38d 32' 26.2\"\n Error:\t 7.1 (arcsec, radius, 90% confidence).\n Detect flag: REASONABLE\n Distance:\t 78 arcsec from the Einstein Probe/WXT position.\n Mean rate:\t (2.4 [+1.6, -1.1])e-3 ct s^-1\n Mean flux:\t (1.02 [+0.70, -0.49])e-13 erg cm^-2 s^-1\n Peak rate:\t (2.4 [+1.6, -1.1])e-3 ct s^-1\n Peak flux:\t (1.02 [+0.70, -0.49])e-13 erg cm^-2 s^-1\n LSXPS UL:\t 3.1e-03 ct/sec, (0.3-10 keV)\n\t so the source is not above this 3-sigma upper limit.\n There is no evidence for fading.\n There is 1 2MASS object within the source's 3-sigma error radius.\n\nAll fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with\ncatalogues and upper limits from other missions, we assumed a power-law spectrum\nwith NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.\n\nThe results of the XRT-team automatic analysis of the XRT observations, including a\nposition-specific upper limit calculator, are available at\nhttps://www.swift.ac.uk/EP.\n\nThis circular is an officicial product of the Swift-XRT team.\n\n\n",
"published": "2025-06-10T08:55:31.550545Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-10T08:55:31.550560Z",
"modified": "2025-06-10T08:55:31.563877Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330243,
"topic": "gcn.circulars",
"uuid": "10103af0-829d-429d-8a1b-3936aa4cb34c",
"title": "EP250610a: Swift-XRT counterpart detection",
"submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"authors": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40662"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40662....1E",
"eventId": "EP250610a",
"subject": "EP250610a: Swift-XRT counterpart detection",
"createdOn": 1749545722912,
"submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
"circularId": 40662,
"submittedHow": "email"
},
"message_text": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P.\nBeardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.\nBurrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),\nP. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro\n(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato\n(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected\nsource EP250610a, collecting 2.1 ks of Photon Counting (PC) mode data between T0+2.8\nks and T0+9.4 ks after the trigger. A candidate counterpart has been found. The\ndetails of this source are:\n\n Source 1 (SWIFT J163325.5+383159):\n ==================================\n RA (J2000.0): 248.3564 =\t16h 33m 25.54s\n Dec (J2000.0): +38.5332 =\t+38d 31' 59.5\"\n Error:\t 4.6 (arcsec, radius, 90% confidence).\n Detect flag: GOOD\n Distance:\t 2.2 arcmin from the Einstein Probe/WXT position.\n Mean rate:\t 0.0111 +/- 0.0027 ct s^-1\n Mean flux:\t (4.4 +/- 1.1)e-13 erg cm^-2 s^-1\n Peak rate:\t 0.0111 +/- 0.0027 ct s^-1\n Peak flux:\t (4.4 +/- 1.1)e-13 erg cm^-2 s^-1\n ECF:\t 3.96e-11 erg cm^-2 ct^-1, assuming NH=1.07e+20 cm^-2,\n\t\t gamma=1.73; determined from a spectral fit.\n LSXPS UL:\t 2.4e-03 ct/sec, (0.3-10 keV)\n\t so the source is 3.1-sigma above this 3-sigma upper limit.\n There is no evidence for fading.\n\n\nWe have detected a total of 2 sources. These have been automatically classified as\nfollows:\n * 0 likely counterparts\n * 1 candidate counterpart\n * 1 uncatalogued X-ray source\n * 0 known X-ray sources\n\nUncatalogued X-ray sources\n--------------------------\n\n Source 2 (SWIFT J163309.1+383226):\n ==================================\n RA (J2000.0): 248.2883 =\t16h 33m 09.19s\n Dec (J2000.0): +38.5406 =\t+38d 32' 26.2\"\n Error:\t 7.1 (arcsec, radius, 90% confidence).\n Detect flag: REASONABLE\n Distance:\t 78 arcsec from the Einstein Probe/WXT position.\n Mean rate:\t (2.4 [+1.6, -1.1])e-3 ct s^-1\n Mean flux:\t (1.02 [+0.70, -0.49])e-13 erg cm^-2 s^-1\n Peak rate:\t (2.4 [+1.6, -1.1])e-3 ct s^-1\n Peak flux:\t (1.02 [+0.70, -0.49])e-13 erg cm^-2 s^-1\n LSXPS UL:\t 3.1e-03 ct/sec, (0.3-10 keV)\n\t so the source is not above this 3-sigma upper limit.\n There is no evidence for fading.\n There is 1 2MASS object within the source's 3-sigma error radius.\n\nAll fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with\ncatalogues and upper limits from other missions, we assumed a power-law spectrum\nwith NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.\n\nThe results of the XRT-team automatic analysis of the XRT observations, including a\nposition-specific upper limit calculator, are available at\nhttps://www.swift.ac.uk/EP.\n\nThis circular is an officicial product of the Swift-XRT team.\n\n\n",
"published": "2025-06-30T08:08:52.259760Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:52.259773Z",
"modified": "2025-06-30T08:08:52.262546Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330226,
"topic": "gcn.circulars",
"uuid": "ce338b1b-de99-413e-9d13-5a39bbb870e3",
"title": "EP250610a: TNG NIR upper limit",
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"authors": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40688"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40688....1B",
"eventId": "EP250610a",
"subject": "EP250610a: TNG NIR upper limit",
"createdOn": 1749642987095,
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"circularId": 40688,
"submittedHow": "web"
},
"message_text": "R. Brivio, P. D'Avanzo, M. Ferro, S. Campana (INAF-OAB), L. Izzo (INAF - OACn), D. B. Malesani (DAWN/NBI & Radboud Univ.), R. Salvaterra (INAF-IASF Milan), A. Melandri (INAF-OAR), V. Lorenzi (INAF-TNG) report on behalf of the CIBO collaboration:\n\n\nWe observed the field of EP250610a detected by EP/WXT (Zhang et al., GCN 40660) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the J filter on 2025-06-11 at a mid-time of about 18.1 hours after the burst. \n\nNo clear afterglow candidate is detected within the XRT position (source 1, Evans et al., GCN 40662) down to a 3-sigma limiting magnitude of J ~ 22 (Vega; calibrated against the 2MASS catalogue).",
"published": "2025-06-30T08:08:51.143790Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:51.143803Z",
"modified": "2025-06-30T08:08:51.146507Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315055,
"topic": "gcn.circulars",
"uuid": "f7ee62e4-c19f-45e4-8652-318fdb7149cf",
"title": "EP250610a: TNG NIR upper limit",
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"authors": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40688"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: TNG NIR upper limit",
"createdOn": 1749642987095,
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"circularId": 40688,
"submittedHow": "web"
},
"message_text": "R. Brivio, P. D'Avanzo, M. Ferro, S. Campana (INAF-OAB), L. Izzo (INAF - OACn), D. B. Malesani (DAWN/NBI & Radboud Univ.), R. Salvaterra (INAF-IASF Milan), A. Melandri (INAF-OAR), V. Lorenzi (INAF-TNG) report on behalf of the CIBO collaboration:\n\n\nWe observed the field of EP250610a detected by EP/WXT (Zhang et al., GCN 40660) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the J filter on 2025-06-11 at a mid-time of about 18.1 hours after the burst. \n\nNo clear afterglow candidate is detected within the XRT position (source 1, Evans et al., GCN 40662) down to a 3-sigma limiting magnitude of J ~ 22 (Vega; calibrated against the 2MASS catalogue).",
"published": "2025-06-29T06:22:09.606516Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.606529Z",
"modified": "2025-06-29T06:22:09.609479Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 203735,
"topic": "gcn.circulars",
"uuid": "5a40f095-11e6-48d8-b699-4041ddab2c05",
"title": "EP250610a: TNG NIR upper limit",
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"authors": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40688"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": "EP250610a: TNG NIR upper limit",
"createdOn": 1749642987095,
"submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
"circularId": 40688,
"submittedHow": "web"
},
"message_text": "R. Brivio, P. D'Avanzo, M. Ferro, S. Campana (INAF-OAB), L. Izzo (INAF - OACn), D. B. Malesani (DAWN/NBI & Radboud Univ.), R. Salvaterra (INAF-IASF Milan), A. Melandri (INAF-OAR), V. Lorenzi (INAF-TNG) report on behalf of the CIBO collaboration:\n\n\nWe observed the field of EP250610a detected by EP/WXT (Zhang et al., GCN 40660) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the J filter on 2025-06-11 at a mid-time of about 18.1 hours after the burst. \n\nNo clear afterglow candidate is detected within the XRT position (source 1, Evans et al., GCN 40662) down to a 3-sigma limiting magnitude of J ~ 22 (Vega; calibrated against the 2MASS catalogue).",
"published": "2025-06-11T11:56:36.124971Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-11T11:56:36.124993Z",
"modified": "2025-06-11T11:56:36.142160Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 209787,
"topic": "gcn.circulars",
"uuid": "21ad30be-f388-4a2b-9cdf-a856631976b3",
"title": " EP250610a: Upper limit from Fermi-GBM Observations",
"submitter": "mariaedvige.ravasio@ru.nl",
"authors": "mariaedvige.ravasio@ru.nl",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40703"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": " EP250610a: Upper limit from Fermi-GBM Observations",
"createdOn": 1749738759938,
"submitter": "mariaedvige.ravasio@ru.nl",
"circularId": 40703,
"submittedHow": "web"
},
"message_text": "M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team:\n\nFermi-GBM had full spatial coverage of the transient EP250610a detected by EP-WXT (Zhang et al., GCN 40660, Lian et al. GCN 40669). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-06-10T04:23:24 UTC.\n\nThe GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient, both temporally and spatially, is identified, as confirmed also by visual inspection of the data.\n\nAssuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 2.8e-08 erg/cm2/s in the energy band 10-1000 keV.\n[1] Goldstein et al. 2019 arXiv:1903.12597",
"published": "2025-06-12T14:32:47.799155Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-12T14:32:47.799167Z",
"modified": "2025-06-12T14:32:47.819181Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315074,
"topic": "gcn.circulars",
"uuid": "dcb1413e-8a27-4d93-b95b-a683c47afd10",
"title": " EP250610a: Upper limit from Fermi-GBM Observations",
"submitter": "mariaedvige.ravasio@ru.nl",
"authors": "mariaedvige.ravasio@ru.nl",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40703"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250610a",
"subject": " EP250610a: Upper limit from Fermi-GBM Observations",
"createdOn": 1749738759938,
"submitter": "mariaedvige.ravasio@ru.nl",
"circularId": 40703,
"submittedHow": "web"
},
"message_text": "M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team:\n\nFermi-GBM had full spatial coverage of the transient EP250610a detected by EP-WXT (Zhang et al., GCN 40660, Lian et al. GCN 40669). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-06-10T04:23:24 UTC.\n\nThe GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient, both temporally and spatially, is identified, as confirmed also by visual inspection of the data.\n\nAssuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 2.8e-08 erg/cm2/s in the energy band 10-1000 keV.\n[1] Goldstein et al. 2019 arXiv:1903.12597",
"published": "2025-06-29T06:22:09.759471Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.759483Z",
"modified": "2025-06-29T06:22:09.762569Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330204,
"topic": "gcn.circulars",
"uuid": "28401134-c4c4-4021-9ebf-a4eb26129d2d",
"title": " EP250610a: Upper limit from Fermi-GBM Observations",
"submitter": "mariaedvige.ravasio@ru.nl",
"authors": "mariaedvige.ravasio@ru.nl",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40703"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40703....1R",
"eventId": "EP250610a",
"subject": " EP250610a: Upper limit from Fermi-GBM Observations",
"createdOn": 1749738759938,
"submitter": "mariaedvige.ravasio@ru.nl",
"circularId": 40703,
"submittedHow": "web"
},
"message_text": "M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team:\n\nFermi-GBM had full spatial coverage of the transient EP250610a detected by EP-WXT (Zhang et al., GCN 40660, Lian et al. GCN 40669). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-06-10T04:23:24 UTC.\n\nThe GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient, both temporally and spatially, is identified, as confirmed also by visual inspection of the data.\n\nAssuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 2.8e-08 erg/cm2/s in the energy band 10-1000 keV.\n[1] Goldstein et al. 2019 arXiv:1903.12597",
"published": "2025-06-30T08:08:45.975903Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:45.975916Z",
"modified": "2025-06-30T08:08:45.978771Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330205,
"topic": "gcn.circulars",
"uuid": "7fc23074-054e-4d2f-b8da-f5adbd4c2f04",
"title": "EP 250612a: AST3-3 Yaoan Optical Observation",
"submitter": "ylhua@pmo.ac.cn",
"authors": "ylhua@pmo.ac.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40709"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40709....1H",
"eventId": "EP250612a",
"subject": "EP 250612a: AST3-3 Yaoan Optical Observation",
"createdOn": 1749746968951,
"submitter": "ylhua@pmo.ac.cn",
"circularId": 40709,
"submittedHow": "web"
},
"message_text": "Yan-Long Hua, Tian-Rui Sun, Lei Hu, Jin-Jun Geng, Xue-Feng Wu (PMO, CAS), report on behalf the AST3 Team:\n \nFollowing the detection of EP 250612a detected by Einstein Probe (Hua et al., GCN 40700), and its potential gamma-ray counterpart by Fermi (Fermi GBM team, GCN 40702), we use Antarctic Survey Telescope 3-3 at Yaoan Astronomy Observation (China, Yunnan) to follow up for the afterglow.\n\nWe observed the target position with 30 x 180s exposure in g-band starting from 2025-06-12T13:12:59.95 about 0.75 hours after the burst.\n\nNo new optical source was detected within the error box (Hua et al., GCN 40700) down to 20.27 mag in the coadd image (total 30x180s, g-band).",
"published": "2025-06-30T08:08:45.982512Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:45.982524Z",
"modified": "2025-06-30T08:08:45.984957Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315081,
"topic": "gcn.circulars",
"uuid": "1e9edeca-155d-4d4d-8946-cbbb66be30d1",
"title": "EP 250612a: AST3-3 Yaoan Optical Observation",
"submitter": "ylhua@pmo.ac.cn",
"authors": "ylhua@pmo.ac.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40709"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP 250612a: AST3-3 Yaoan Optical Observation",
"createdOn": 1749746968951,
"submitter": "ylhua@pmo.ac.cn",
"circularId": 40709,
"submittedHow": "web"
},
"message_text": "Yan-Long Hua, Tian-Rui Sun, Lei Hu, Jin-Jun Geng, Xue-Feng Wu (PMO, CAS), report on behalf the AST3 Team:\n \nFollowing the detection of EP 250612a detected by Einstein Probe (Hua et al., GCN 40700), and its potential gamma-ray counterpart by Fermi (Fermi GBM team, GCN 40702), we use Antarctic Survey Telescope 3-3 at Yaoan Astronomy Observation (China, Yunnan) to follow up for the afterglow.\n\nWe observed the target position with 30 x 180s exposure in g-band starting from 2025-06-12T13:12:59.95 about 0.75 hours after the burst.\n\nNo new optical source was detected within the error box (Hua et al., GCN 40700) down to 20.27 mag in the coadd image (total 30x180s, g-band).",
"published": "2025-06-29T06:22:09.817919Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.817934Z",
"modified": "2025-06-29T06:22:09.821123Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 210425,
"topic": "gcn.circulars",
"uuid": "60c250ec-a28c-4f5e-bd49-e3bee8206f3c",
"title": "EP 250612a: AST3-3 Yaoan Optical Observation",
"submitter": "ylhua@pmo.ac.cn",
"authors": "ylhua@pmo.ac.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40709"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP 250612a: AST3-3 Yaoan Optical Observation",
"createdOn": 1749746968951,
"submitter": "ylhua@pmo.ac.cn",
"circularId": 40709,
"submittedHow": "web"
},
"message_text": "Yan-Long Hua, Tian-Rui Sun, Lei Hu, Jin-Jun Geng, Xue-Feng Wu (PMO, CAS), report on behalf the AST3 Team:\n \nFollowing the detection of EP 250612a detected by Einstein Probe (Hua et al., GCN 40700), and its potential gamma-ray counterpart by Fermi (Fermi GBM team, GCN 40702), we use Antarctic Survey Telescope 3-3 at Yaoan Astronomy Observation (China, Yunnan) to follow up for the afterglow.\n\nWe observed the target position with 30 x 180s exposure in g-band starting from 2025-06-12T13:12:59.95 about 0.75 hours after the burst.\n\nNo new optical source was detected within the error box (Hua et al., GCN 40700) down to 20.27 mag in the coadd image (total 30x180s, g-band).",
"published": "2025-06-12T16:49:37.853347Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-12T16:49:37.853362Z",
"modified": "2025-06-12T16:49:37.863517Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 209379,
"topic": "gcn.circulars",
"uuid": "e5fb3cb8-b727-4391-a93e-487889363e7f",
"title": "EP250612a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40700"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: Einstein Probe detection of an X-ray transient",
"createdOn": 1749733393864,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40700,
"submittedHow": "web"
},
"message_text": "Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250612a. The transient triggered EP-WXT (ID: 01709178580) at 2025-06-12T12:28:05 (UTC). The WXT position of the source is R.A. = 229.654 deg, DEC = -26.757 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 229.6503 deg, DEC = -26.7661 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nFurther information will be updated when the telemetry data is received. \n\nThe contact TA of EP250612a is Y. L. Hua, please contact him via email ylhua@pmo.ac.cn if needed. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n",
"published": "2025-06-12T13:03:23.046873Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-12T13:03:23.046888Z",
"modified": "2025-06-12T13:03:23.058501Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315069,
"topic": "gcn.circulars",
"uuid": "0ef17342-e088-4e04-9702-8bfc255670f8",
"title": "EP250612a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40700"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: Einstein Probe detection of an X-ray transient",
"createdOn": 1749733393864,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40700,
"submittedHow": "web"
},
"message_text": "Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250612a. The transient triggered EP-WXT (ID: 01709178580) at 2025-06-12T12:28:05 (UTC). The WXT position of the source is R.A. = 229.654 deg, DEC = -26.757 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 229.6503 deg, DEC = -26.7661 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nFurther information will be updated when the telemetry data is received. \n\nThe contact TA of EP250612a is Y. L. Hua, please contact him via email ylhua@pmo.ac.cn if needed. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n",
"published": "2025-06-29T06:22:09.718986Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.718999Z",
"modified": "2025-06-29T06:22:09.721976Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330287,
"topic": "gcn.circulars",
"uuid": "412bd9e1-54e0-486e-91b3-1039d42c411c",
"title": "EP250612a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40700"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40700....1H",
"eventId": "EP250612a",
"subject": "EP250612a: Einstein Probe detection of an X-ray transient",
"createdOn": 1749733393864,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40700,
"submittedHow": "web"
},
"message_text": "Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250612a. The transient triggered EP-WXT (ID: 01709178580) at 2025-06-12T12:28:05 (UTC). The WXT position of the source is R.A. = 229.654 deg, DEC = -26.757 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 229.6503 deg, DEC = -26.7661 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nFurther information will be updated when the telemetry data is received. \n\nThe contact TA of EP250612a is Y. L. Hua, please contact him via email ylhua@pmo.ac.cn if needed. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).\n",
"published": "2025-06-30T08:09:07.588070Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:09:07.588082Z",
"modified": "2025-06-30T08:09:07.590392Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330208,
"topic": "gcn.circulars",
"uuid": "6539c26b-1a3f-426a-874e-bc8c509e6d0b",
"title": "EP250612a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40714"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40714....1L",
"eventId": "EP250612a",
"subject": "EP250612a: Global MASTER-Net observations report",
"createdOn": 1749767781617,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40714,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250612a ( EP Team et al., GCN 40700) errorbox 33238 sec after notice time and 35413 sec after trigger time at 2025-06-12 22:18:18 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 24 deg. The sun altitude is -80.1 deg. \n\nThe galactic latitude b = 25 deg., longitude l = 340 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2901165\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 17m 45.90s , -26d 51m 07.4s) | C | 60 | 18.5 | \n 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 15m 46.32s , -26d 35m 46.7s) | C | 60 | 18.8 | \n 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 17m 42.75s , -26d 50m 04.0s) | C | 60 | 18.6 | \n 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 15m 43.63s , -26d 34m 41.7s) | C | 60 | 18.9 | \n 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 17m 49.62s , -26d 49m 56.6s) | C | 60 | 18.6 | \n 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 15m 50.50s , -26d 34m 33.7s) | C | 60 | 18.8 | \n 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 17m 48.24s , -26d 50m 30.1s) | C | 60 | 18.6 | \n 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 15m 49.05s , -26d 35m 06.7s) | C | 60 | 18.8 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-06-30T08:08:46.003435Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:46.003449Z",
"modified": "2025-06-30T08:08:46.007616Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 211992,
"topic": "gcn.circulars",
"uuid": "3c05e495-8f45-47a4-87d9-76fd4b2a0a24",
"title": "EP250612a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40714"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: Global MASTER-Net observations report",
"createdOn": 1749767781617,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40714,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250612a ( EP Team et al., GCN 40700) errorbox 33238 sec after notice time and 35413 sec after trigger time at 2025-06-12 22:18:18 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 24 deg. The sun altitude is -80.1 deg. \n\nThe galactic latitude b = 25 deg., longitude l = 340 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2901165\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 17m 45.90s , -26d 51m 07.4s) | C | 60 | 18.5 | \n 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 15m 46.32s , -26d 35m 46.7s) | C | 60 | 18.8 | \n 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 17m 42.75s , -26d 50m 04.0s) | C | 60 | 18.6 | \n 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 15m 43.63s , -26d 34m 41.7s) | C | 60 | 18.9 | \n 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 17m 49.62s , -26d 49m 56.6s) | C | 60 | 18.6 | \n 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 15m 50.50s , -26d 34m 33.7s) | C | 60 | 18.8 | \n 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 17m 48.24s , -26d 50m 30.1s) | C | 60 | 18.6 | \n 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 15m 49.05s , -26d 35m 06.7s) | C | 60 | 18.8 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-06-12T22:36:30.608001Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-12T22:36:30.608015Z",
"modified": "2025-06-12T22:36:30.632705Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315087,
"topic": "gcn.circulars",
"uuid": "79a00954-0dfb-43bb-82ce-05c59489a3f9",
"title": "EP250612a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
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"gcn_circular": "https://gcn.nasa.gov/circulars/40714"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: Global MASTER-Net observations report",
"createdOn": 1749767781617,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40714,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250612a ( EP Team et al., GCN 40700) errorbox 33238 sec after notice time and 35413 sec after trigger time at 2025-06-12 22:18:18 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 24 deg. The sun altitude is -80.1 deg. \n\nThe galactic latitude b = 25 deg., longitude l = 340 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2901165\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 17m 45.90s , -26d 51m 07.4s) | C | 60 | 18.5 | \n 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 15m 46.32s , -26d 35m 46.7s) | C | 60 | 18.8 | \n 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 17m 42.75s , -26d 50m 04.0s) | C | 60 | 18.6 | \n 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 15m 43.63s , -26d 34m 41.7s) | C | 60 | 18.9 | \n 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 17m 49.62s , -26d 49m 56.6s) | C | 60 | 18.6 | \n 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 15m 50.50s , -26d 34m 33.7s) | C | 60 | 18.8 | \n 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 17m 48.24s , -26d 50m 30.1s) | C | 60 | 18.6 | \n 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 15m 49.05s , -26d 35m 06.7s) | C | 60 | 18.8 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-06-29T06:22:09.867296Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.867312Z",
"modified": "2025-06-29T06:22:09.870342Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330174,
"topic": "gcn.circulars",
"uuid": "d7875cf3-0234-4168-9729-5738e37f0f2e",
"title": "EP250612a/GRB 250612B: JinShan optical upper limit",
"submitter": "liuxing@nao.cas.cn",
"authors": "liuxing@nao.cas.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40710"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40710....1L",
"eventId": "EP250612a",
"subject": "EP250612a/GRB 250612B: JinShan optical upper limit",
"createdOn": 1749749075131,
"submitter": "liuxing@nao.cas.cn",
"circularId": 40710,
"submittedHow": "web"
},
"message_text": "X. Liu, Z.P. Zhu, J. An, S.Q. Jiang, D. Xu (NAOC), S.Y. Fu(HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:\n\nWe observed the field of EP250612a detected by EP/WXT (Hua et al., GCN 40700), which is very likely GRB 250612B by Fermi/GBM (Preis & Greiner, GCN 40701; Fermi GBM tea, GCN 40702), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:45:13 UT on 2025-06-12, i.e., 3.29 hr after the EP trigger, and 18 x 200 s frames were obtained in the Sloan i-band.\n\nNo new optical source is detected within the EP/FXT error circle (Hua et al., GCN 40700), down to a 3-sigma upper limit of i ~ 20.2 mag (AB), calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.\n\nWe acknowledge the excellent support from T.Q. Chen for enabling these observations.",
"published": "2025-06-30T08:08:43.763052Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:43.763069Z",
"modified": "2025-06-30T08:08:43.766236Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315082,
"topic": "gcn.circulars",
"uuid": "6d155cd5-48b4-402a-8338-b2899db3a35c",
"title": "EP250612a/GRB 250612B: JinShan optical upper limit",
"submitter": "liuxing@nao.cas.cn",
"authors": "liuxing@nao.cas.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40710"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a/GRB 250612B: JinShan optical upper limit",
"createdOn": 1749749075131,
"submitter": "liuxing@nao.cas.cn",
"circularId": 40710,
"submittedHow": "web"
},
"message_text": "X. Liu, Z.P. Zhu, J. An, S.Q. Jiang, D. Xu (NAOC), S.Y. Fu(HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:\n\nWe observed the field of EP250612a detected by EP/WXT (Hua et al., GCN 40700), which is very likely GRB 250612B by Fermi/GBM (Preis & Greiner, GCN 40701; Fermi GBM tea, GCN 40702), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:45:13 UT on 2025-06-12, i.e., 3.29 hr after the EP trigger, and 18 x 200 s frames were obtained in the Sloan i-band.\n\nNo new optical source is detected within the EP/FXT error circle (Hua et al., GCN 40700), down to a 3-sigma upper limit of i ~ 20.2 mag (AB), calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.\n\nWe acknowledge the excellent support from T.Q. Chen for enabling these observations.",
"published": "2025-06-29T06:22:09.829187Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.829200Z",
"modified": "2025-06-29T06:22:09.834216Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 210584,
"topic": "gcn.circulars",
"uuid": "b99e61b3-7cce-4fb1-86ec-8a2a55a7570d",
"title": "EP250612a/GRB 250612B: JinShan optical upper limit",
"submitter": "liuxing@nao.cas.cn",
"authors": "liuxing@nao.cas.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40710"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a/GRB 250612B: JinShan optical upper limit",
"createdOn": 1749749075131,
"submitter": "liuxing@nao.cas.cn",
"circularId": 40710,
"submittedHow": "web"
},
"message_text": "X. Liu, Z.P. Zhu, J. An, S.Q. Jiang, D. Xu (NAOC), S.Y. Fu(HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:\n\nWe observed the field of EP250612a detected by EP/WXT (Hua et al., GCN 40700), which is very likely GRB 250612B by Fermi/GBM (Preis & Greiner, GCN 40701; Fermi GBM tea, GCN 40702), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:45:13 UT on 2025-06-12, i.e., 3.29 hr after the EP trigger, and 18 x 200 s frames were obtained in the Sloan i-band.\n\nNo new optical source is detected within the EP/FXT error circle (Hua et al., GCN 40700), down to a 3-sigma upper limit of i ~ 20.2 mag (AB), calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.\n\nWe acknowledge the excellent support from T.Q. Chen for enabling these observations.",
"published": "2025-06-12T17:24:44.759162Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-12T17:24:44.759175Z",
"modified": "2025-06-12T17:24:44.776043Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315101,
"topic": "gcn.circulars",
"uuid": "1caa8c77-6b1a-4b80-a0c9-7ba9e488f3aa",
"title": "EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate",
"submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"authors": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40727"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate",
"createdOn": 1749889774614,
"submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"circularId": 40727,
"submittedHow": "web"
},
"message_text": "A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), D. Xu (NAOC), L. Cotter (UCD), B. P. Gompertz (U. Birmingham), A. A. Djupvik (NOT), L. Fuglsang (NOT), report on behalf of a larger collaboration.\n\nWe observed the field of EP250612a / GRB 250612B detected by EP (Hua et al., GCN 40700) and Fermi (Fermi GBM team, GCN 40702), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 12x100 s exposures in the SDSS r-band, starting at 23:19 UT on 2025-05-13 (1.952 days after the EP trigger).\n\nAt J2000 coordinates RA:15:18:36.667, DEC: -26:46:03.624 (error 0.5”), consistent with those by Li et al. (GCN 40716), the optical counterpart is detected in our stacked image with a preliminary magnitude:\n\nr = 23.59 +/- 0.22 (AB).\n\nThe photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction.",
"published": "2025-06-29T06:22:09.973861Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.973873Z",
"modified": "2025-06-29T06:22:09.976518Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 221162,
"topic": "gcn.circulars",
"uuid": "76110a19-d81f-4ce3-871e-e2d84c4dca9c",
"title": "EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate",
"submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"authors": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40727"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate",
"createdOn": 1749889774614,
"submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"circularId": 40727,
"submittedHow": "web"
},
"message_text": "A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), D. Xu (NAOC), L. Cotter (UCD), B. P. Gompertz (U. Birmingham), A. A. Djupvik (NOT), L. Fuglsang (NOT), report on behalf of a larger collaboration.\n\nWe observed the field of EP250612a / GRB 250612B detected by EP (Hua et al., GCN 40700) and Fermi (Fermi GBM team, GCN 40702), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 12x100 s exposures in the SDSS r-band, starting at 23:19 UT on 2025-05-13 (1.952 days after the EP trigger).\n\nAt J2000 coordinates RA:15:18:36.667, DEC: -26:46:03.624 (error 0.5”), consistent with those by Li et al. (GCN 40716), the optical counterpart is detected in our stacked image with a preliminary magnitude:\n\nr = 23.59 +/- 0.22 (AB).\n\nThe photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction.",
"published": "2025-06-14T08:29:43.287275Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-14T08:29:43.287296Z",
"modified": "2025-06-14T08:29:43.298250Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330211,
"topic": "gcn.circulars",
"uuid": "7b1a5422-e2c0-4f3f-a51d-e29e29078bf3",
"title": "EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate",
"submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"authors": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40727"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40727....1D",
"eventId": "EP250612a",
"subject": "EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate",
"createdOn": 1749889774614,
"submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
"circularId": 40727,
"submittedHow": "web"
},
"message_text": "A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), D. Xu (NAOC), L. Cotter (UCD), B. P. Gompertz (U. Birmingham), A. A. Djupvik (NOT), L. Fuglsang (NOT), report on behalf of a larger collaboration.\n\nWe observed the field of EP250612a / GRB 250612B detected by EP (Hua et al., GCN 40700) and Fermi (Fermi GBM team, GCN 40702), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 12x100 s exposures in the SDSS r-band, starting at 23:19 UT on 2025-05-13 (1.952 days after the EP trigger).\n\nAt J2000 coordinates RA:15:18:36.667, DEC: -26:46:03.624 (error 0.5”), consistent with those by Li et al. (GCN 40716), the optical counterpart is detected in our stacked image with a preliminary magnitude:\n\nr = 23.59 +/- 0.22 (AB).\n\nThe photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction.",
"published": "2025-06-30T08:08:46.029891Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:46.029903Z",
"modified": "2025-06-30T08:08:46.032527Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315094,
"topic": "gcn.circulars",
"uuid": "ebdbd350-bf57-47b9-88c5-26f72f1ec175",
"title": "EP250612a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40720"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1749823656314,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40720,
"submittedHow": "web"
},
"message_text": "Y.L.Hua (PMO, CAS), J. W. Hu, T. Zhao, Y. J. Song ,W. Yuan(NAO, CAS) report on behalf of the Einstein Probe team:\n \nThe fast X-ray transient EP250612a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hua et al., GCN 40700), and followed up by several optical and X-ray telescopes (Hua et al., GCN 40709, Li et al., GCN 40716). Refined analysis of the WXT data shows that the event started at T0=2025-06-12T12:27:38 (UTC) and lasted for about 35s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 3.9 x 10^-8 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 4.3 x 10^21 cm^-2(-2.1, +2.4) and a photon index of 1.01 (-0.1, +0.1). The derived average unabsorbed 0.5-4 keV flux is 3.67 (-0.74, +1.10) x 10^-9 erg/s/cm^2.\n \nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-12 12:30:08, about 3 minutes after T0, with an exposure time of 5858 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 229.6534, DEC = -26.7673 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Fermi(Fermi GBM team., GCN 40702). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 1.49 x 10^21 cm^-2 and a photon index of 2.2 (-0.045, +0.045). The derived unabsorbed 0.5-10 keV flux is 1.37 (-0.03, +0.04) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters.\n \n \nEP-FXT will continue monitoring the source in the forthcoming days. Multi-band follow-up observations are encouraged. The contact TA of EP250612a is Y.L.Hua, please contact him via the email ylhua@pmo.ac.cn if needed.\n \nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-29T06:22:09.921926Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.921939Z",
"modified": "2025-06-29T06:22:09.924951Z",
"nonlocalizedevents": [],
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},
{
"id": 330232,
"topic": "gcn.circulars",
"uuid": "6c6fd811-0f33-4edd-9fce-29bfd6c428ab",
"title": "EP250612a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40720"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40720....1H",
"eventId": "EP250612a",
"subject": "EP250612a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1749823656314,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40720,
"submittedHow": "web"
},
"message_text": "Y.L.Hua (PMO, CAS), J. W. Hu, T. Zhao, Y. J. Song ,W. Yuan(NAO, CAS) report on behalf of the Einstein Probe team:\n \nThe fast X-ray transient EP250612a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hua et al., GCN 40700), and followed up by several optical and X-ray telescopes (Hua et al., GCN 40709, Li et al., GCN 40716). Refined analysis of the WXT data shows that the event started at T0=2025-06-12T12:27:38 (UTC) and lasted for about 35s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 3.9 x 10^-8 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 4.3 x 10^21 cm^-2(-2.1, +2.4) and a photon index of 1.01 (-0.1, +0.1). The derived average unabsorbed 0.5-4 keV flux is 3.67 (-0.74, +1.10) x 10^-9 erg/s/cm^2.\n \nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-12 12:30:08, about 3 minutes after T0, with an exposure time of 5858 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 229.6534, DEC = -26.7673 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Fermi(Fermi GBM team., GCN 40702). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 1.49 x 10^21 cm^-2 and a photon index of 2.2 (-0.045, +0.045). The derived unabsorbed 0.5-10 keV flux is 1.37 (-0.03, +0.04) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters.\n \n \nEP-FXT will continue monitoring the source in the forthcoming days. Multi-band follow-up observations are encouraged. The contact TA of EP250612a is Y.L.Hua, please contact him via the email ylhua@pmo.ac.cn if needed.\n \nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-30T08:08:51.185114Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:51.185127Z",
"modified": "2025-06-30T08:08:51.187781Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 216194,
"topic": "gcn.circulars",
"uuid": "8b64679c-87af-4337-9f12-dc2e346657d8",
"title": "EP250612a: refined analysis of the EP-WXT and EP-FXT observations",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40720"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: refined analysis of the EP-WXT and EP-FXT observations",
"createdOn": 1749823656314,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40720,
"submittedHow": "web"
},
"message_text": "Y.L.Hua (PMO, CAS), J. W. Hu, T. Zhao, Y. J. Song ,W. Yuan(NAO, CAS) report on behalf of the Einstein Probe team:\n \nThe fast X-ray transient EP250612a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hua et al., GCN 40700), and followed up by several optical and X-ray telescopes (Hua et al., GCN 40709, Li et al., GCN 40716). Refined analysis of the WXT data shows that the event started at T0=2025-06-12T12:27:38 (UTC) and lasted for about 35s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 3.9 x 10^-8 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 4.3 x 10^21 cm^-2(-2.1, +2.4) and a photon index of 1.01 (-0.1, +0.1). The derived average unabsorbed 0.5-4 keV flux is 3.67 (-0.74, +1.10) x 10^-9 erg/s/cm^2.\n \nThe Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-12 12:30:08, about 3 minutes after T0, with an exposure time of 5858 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 229.6534, DEC = -26.7673 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Fermi(Fermi GBM team., GCN 40702). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 1.49 x 10^21 cm^-2 and a photon index of 2.2 (-0.045, +0.045). The derived unabsorbed 0.5-10 keV flux is 1.37 (-0.03, +0.04) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters.\n \n \nEP-FXT will continue monitoring the source in the forthcoming days. Multi-band follow-up observations are encouraged. The contact TA of EP250612a is Y.L.Hua, please contact him via the email ylhua@pmo.ac.cn if needed.\n \nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-13T14:07:46.401994Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-13T14:07:46.402007Z",
"modified": "2025-06-13T14:07:46.409037Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 213116,
"topic": "gcn.circulars",
"uuid": "3385b1e2-df2f-4677-80ca-f9467939a27d",
"title": "EP250612a: SVOM/VT optical candidate",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40716"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: SVOM/VT optical candidate",
"createdOn": 1749782704578,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 40716,
"submittedHow": "web"
},
"message_text": "H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) report on behalf of the SVOM and EP Teams: \n\nSVOM/VT observed the field of EP250612a (Hua et al., GCN 40700) in ToO mode \nin the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. \nThe observation started at 2025-06-12T21:08:02 UT, about 8.67 hours after the trigger time. \n\nOne uncatalogued source, compared to Legacy Survey, was detected within FXT error circle (Hua et al., GCN 40700), RA = 229.65265, DEC = -26.76771, corresponding to:\n R. A. (J2000) = 15:18:36.6 \n DEC. (J2000) = -26:46:03.8\nError = 0.5 arcseconds\n\nThe brightness of the candidate is derived as below :\n mid-time band mag(AB) exposure\n 9.45 hour VT_B 22.3+/-0.1 20*70 sec\n 9.46 hour VT_R 21.8+/-0.1 19*70 sec\n\nOur photometry was derived in AB magnitude and not corrected for Galactic extinction.\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.",
"published": "2025-06-13T02:45:12.161251Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-13T02:45:12.161262Z",
"modified": "2025-06-13T02:45:12.173049Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315089,
"topic": "gcn.circulars",
"uuid": "17372800-d438-4101-a723-5d2a2fff37a5",
"title": "EP250612a: SVOM/VT optical candidate",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
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},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250612a",
"subject": "EP250612a: SVOM/VT optical candidate",
"createdOn": 1749782704578,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 40716,
"submittedHow": "web"
},
"message_text": "H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) report on behalf of the SVOM and EP Teams: \n\nSVOM/VT observed the field of EP250612a (Hua et al., GCN 40700) in ToO mode \nin the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. \nThe observation started at 2025-06-12T21:08:02 UT, about 8.67 hours after the trigger time. \n\nOne uncatalogued source, compared to Legacy Survey, was detected within FXT error circle (Hua et al., GCN 40700), RA = 229.65265, DEC = -26.76771, corresponding to:\n R. A. (J2000) = 15:18:36.6 \n DEC. (J2000) = -26:46:03.8\nError = 0.5 arcseconds\n\nThe brightness of the candidate is derived as below :\n mid-time band mag(AB) exposure\n 9.45 hour VT_B 22.3+/-0.1 20*70 sec\n 9.46 hour VT_R 21.8+/-0.1 19*70 sec\n\nOur photometry was derived in AB magnitude and not corrected for Galactic extinction.\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.",
"published": "2025-06-29T06:22:09.881782Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:09.881794Z",
"modified": "2025-06-29T06:22:09.887172Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330291,
"topic": "gcn.circulars",
"uuid": "b7a4541e-66c2-4994-9c4b-a0ae78547bb9",
"title": "EP250612a: SVOM/VT optical candidate",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40716"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40716....1L",
"eventId": "EP250612a",
"subject": "EP250612a: SVOM/VT optical candidate",
"createdOn": 1749782704578,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 40716,
"submittedHow": "web"
},
"message_text": "H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) report on behalf of the SVOM and EP Teams: \n\nSVOM/VT observed the field of EP250612a (Hua et al., GCN 40700) in ToO mode \nin the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. \nThe observation started at 2025-06-12T21:08:02 UT, about 8.67 hours after the trigger time. \n\nOne uncatalogued source, compared to Legacy Survey, was detected within FXT error circle (Hua et al., GCN 40700), RA = 229.65265, DEC = -26.76771, corresponding to:\n R. A. (J2000) = 15:18:36.6 \n DEC. (J2000) = -26:46:03.8\nError = 0.5 arcseconds\n\nThe brightness of the candidate is derived as below :\n mid-time band mag(AB) exposure\n 9.45 hour VT_B 22.3+/-0.1 20*70 sec\n 9.46 hour VT_R 21.8+/-0.1 19*70 sec\n\nOur photometry was derived in AB magnitude and not corrected for Galactic extinction.\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.",
"published": "2025-06-30T08:09:07.613213Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:09:07.613225Z",
"modified": "2025-06-30T08:09:07.615838Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 234527,
"topic": "gcn.circulars",
"uuid": "f1618d68-0086-4d11-97a2-5a145810f3cd",
"title": "EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40743"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250615a",
"subject": "EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient",
"createdOn": 1750066270211,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40743,
"submittedHow": "web"
},
"message_text": "G. J. Yang, M. J. Liu (NAO, CAS), Y. Q. Zhao (USTC,PRIC), Y. P. Zhou (NJU), X. L. Chen (YNU), Q. Y. Wu, C. C. Jin (NAO,CAS) on behalf of the Einstein Probe team:\n\nWe report on the detection of a fast X-ray transient, designated EP250615a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2025-06-15T22:25:17 (UTC). The position of the source is R.A. = 290.379 deg, DEC = 4.678 deg (J2000) with an uncertainty of 2.181 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for more than 50 seconds. The lightcurve of the transient observed by the WXT exhibits a rapid brightening profile. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 2.2 (+1.5/-1.4) with a column density value of 2.1 (+1.7/-1.6) x 10^22 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 1.0 (+4.3/-0.6) x 10^-8 erg/s/cm^2. The peak flux is around 6.3 x 10^-7 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The trigger time and position of this X-ray transient are consistent with that of GRB 250615A (GCN 40736, GCN 40737, GCN 40739).\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-16T09:31:19.383527Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-16T09:31:19.383548Z",
"modified": "2025-06-16T09:31:19.526929Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 330235,
"topic": "gcn.circulars",
"uuid": "f745015a-26f5-4801-8cac-fe6c634ffa7f",
"title": "EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40743"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40743....1Y",
"eventId": "EP250615a",
"subject": "EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient",
"createdOn": 1750066270211,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40743,
"submittedHow": "web"
},
"message_text": "G. J. Yang, M. J. Liu (NAO, CAS), Y. Q. Zhao (USTC,PRIC), Y. P. Zhou (NJU), X. L. Chen (YNU), Q. Y. Wu, C. C. Jin (NAO,CAS) on behalf of the Einstein Probe team:\n\nWe report on the detection of a fast X-ray transient, designated EP250615a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2025-06-15T22:25:17 (UTC). The position of the source is R.A. = 290.379 deg, DEC = 4.678 deg (J2000) with an uncertainty of 2.181 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for more than 50 seconds. The lightcurve of the transient observed by the WXT exhibits a rapid brightening profile. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 2.2 (+1.5/-1.4) with a column density value of 2.1 (+1.7/-1.6) x 10^22 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 1.0 (+4.3/-0.6) x 10^-8 erg/s/cm^2. The peak flux is around 6.3 x 10^-7 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The trigger time and position of this X-ray transient are consistent with that of GRB 250615A (GCN 40736, GCN 40737, GCN 40739).\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-30T08:08:51.204101Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-30T08:08:51.204113Z",
"modified": "2025-06-30T08:08:51.206691Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 315117,
"topic": "gcn.circulars",
"uuid": "6f21c142-f866-4c58-91a6-695288a4ec75",
"title": "EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40743"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250615a",
"subject": "EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient",
"createdOn": 1750066270211,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40743,
"submittedHow": "web"
},
"message_text": "G. J. Yang, M. J. Liu (NAO, CAS), Y. Q. Zhao (USTC,PRIC), Y. P. Zhou (NJU), X. L. Chen (YNU), Q. Y. Wu, C. C. Jin (NAO,CAS) on behalf of the Einstein Probe team:\n\nWe report on the detection of a fast X-ray transient, designated EP250615a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2025-06-15T22:25:17 (UTC). The position of the source is R.A. = 290.379 deg, DEC = 4.678 deg (J2000) with an uncertainty of 2.181 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for more than 50 seconds. The lightcurve of the transient observed by the WXT exhibits a rapid brightening profile. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 2.2 (+1.5/-1.4) with a column density value of 2.1 (+1.7/-1.6) x 10^22 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 1.0 (+4.3/-0.6) x 10^-8 erg/s/cm^2. The peak flux is around 6.3 x 10^-7 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The trigger time and position of this X-ray transient are consistent with that of GRB 250615A (GCN 40736, GCN 40737, GCN 40739).\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-06-29T06:22:10.114070Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-06-29T06:22:10.114083Z",
"modified": "2025-06-29T06:22:10.117405Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 348805,
"topic": "gcn.circulars",
"uuid": "0a3e3342-95ac-4c09-b940-5e2b9ffa87d9",
"title": "EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40906"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E",
"createdOn": 1751516400962,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40906,
"submittedHow": "web"
},
"message_text": "H. Q. Cheng (NAO, CAS), G. Y. Zhao (SYSU), C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), Y. J. Zhang (THU), J. W. Hu, H. Sun and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250702a. The source was first detected in an observation starting at 2025-07-02T02:53:44 (UTC), and was continuously detected in subsequent observations spanning from 2025-07-02T05:57:06 to 2025-07-02T22:32:44. The WXT position of the source is R.A. = 284.700 deg, DEC = -7.869 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The source reached a peak flux in the observation starting at 2025-07-02T16:10:11 with an exposure of 827s, the epoch of which is generally consistent with the burst time of GRB 250702E (GCN 40890). Considering that EP250702a is spatially and temporally coincident with the GRB 250702B,C,D,E detected by Fermi /GBM (GCN 40883, 40885, 40886, 40890, 40891), we suggest that EP250702a is likely the X-ray source associated with GRB 250702B,C,D,E. The WXT position is also consistent with the source localization skymap provided by the Swift/BAT-GUANO (GCN 40903).\n\nStacking of the WXT data taken prior to the WXT detection indicated that the source has already emerged on July 1st, 2025. The WXT spectrum of the peak flux epoch can be fitted with an absorbed power-law model (with the column density fixed at the Galactic absorption value of 5e21 cm^-2), yielding a photon index of 0.2+/-0.1 and an unabsorbed 0.5-4 keV flux of (5.5+/-0.7)e-10 ergs/s/cm^2. \n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) onboard EP was performed but the telemetry data is still not available yet. The FXT onboard source detection algorithm gives an improved source position at R.A. = 284.6911 deg, DEC = -7.8715 deg (J2000) with an uncertainty of 20 arcsecond in radius (90% C.L. statistical and systematic). More information will be updated when the telemetry data is received.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics)",
"published": "2025-07-03T04:20:09.717578Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-03T04:20:09.717594Z",
"modified": "2025-07-03T04:20:09.721742Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421045,
"topic": "gcn.circulars",
"uuid": "1871628e-6a11-43f3-a60d-e8b6f5ecef37",
"title": "EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40906"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40906....1C",
"eventId": "EP250702a",
"subject": "EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E",
"createdOn": 1751516400962,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40906,
"submittedHow": "web"
},
"message_text": "H. Q. Cheng (NAO, CAS), G. Y. Zhao (SYSU), C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), Y. J. Zhang (THU), J. W. Hu, H. Sun and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250702a. The source was first detected in an observation starting at 2025-07-02T02:53:44 (UTC), and was continuously detected in subsequent observations spanning from 2025-07-02T05:57:06 to 2025-07-02T22:32:44. The WXT position of the source is R.A. = 284.700 deg, DEC = -7.869 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The source reached a peak flux in the observation starting at 2025-07-02T16:10:11 with an exposure of 827s, the epoch of which is generally consistent with the burst time of GRB 250702E (GCN 40890). Considering that EP250702a is spatially and temporally coincident with the GRB 250702B,C,D,E detected by Fermi /GBM (GCN 40883, 40885, 40886, 40890, 40891), we suggest that EP250702a is likely the X-ray source associated with GRB 250702B,C,D,E. The WXT position is also consistent with the source localization skymap provided by the Swift/BAT-GUANO (GCN 40903).\n\nStacking of the WXT data taken prior to the WXT detection indicated that the source has already emerged on July 1st, 2025. The WXT spectrum of the peak flux epoch can be fitted with an absorbed power-law model (with the column density fixed at the Galactic absorption value of 5e21 cm^-2), yielding a photon index of 0.2+/-0.1 and an unabsorbed 0.5-4 keV flux of (5.5+/-0.7)e-10 ergs/s/cm^2. \n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) onboard EP was performed but the telemetry data is still not available yet. The FXT onboard source detection algorithm gives an improved source position at R.A. = 284.6911 deg, DEC = -7.8715 deg (J2000) with an uncertainty of 20 arcsecond in radius (90% C.L. statistical and systematic). More information will be updated when the telemetry data is received.\n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics)",
"published": "2025-07-14T08:07:55.814187Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:07:55.814199Z",
"modified": "2025-07-14T08:07:55.817521Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 403884,
"topic": "gcn.circulars",
"uuid": "67572201-771f-429e-a06c-f31cd928ea1e",
"title": "EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes",
"submitter": "David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>",
"authors": "David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41067"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes",
"createdOn": 1752253316463,
"submitter": "David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>",
"circularId": 41067,
"submittedHow": "web"
},
"message_text": "D. Paneque (MPP Munich), M. Teshima (MPP Munich), Arnau Aguasca-Cabot (UB, ICCUB, and IEEC-UB), Alessio Berti (MPP Munich), Sweta Menon (UNIROMA2 & INAF), Edna Ruiz-Velasco (LAPP Annecy), Monica Seglar-Arroyo (IFAE Barcelona) and Andrea Simongini (UNIROMA2 & INAF), on behalf of the CTAO-LST and MAGIC Collaborations report:\n\nWe observed the field of EP250702a / GRBs 250702B,D,E (GCN 40883, 40886, 40890, 40891, 40906). A total of 2.94 hours of observations were conducted with the MAGIC telescopes, beginning at 2025-07-04 01:25:53 UTC. The final 1.79 hours of this period were carried out jointly with LST-1. \n\nA preliminary offline analysis of the LST-1 and MAGIC dataset shows no excess of gamma rays above 200 GeV in the field of EP250702a (GCN 40906). These results have been obtained using the LST analysis software, lst-chain (LST Collaboration, 2023 ApJ 956 80, v0.10.7), and the MAGIC analysis software MARS (Zanin et al. 2013, v 3.2.1). Observations were affected by reduced atmospheric transparency. A more in-depth analysis of this data set is ongoing.\n\nSubsequent observations are planned after the moonbreak, subject to the nature of upcoming detections.\n\nLST-1 is a prototype of the Large-Sized Telescope (LST) for the Cherenkov Telescope Array Observatory, and is located on the Canary island of La Palma, Spain. The telescope design is optimized for observation of gamma rays in the range from 20 GeV to 3 TeV.\n\nMAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV.\n",
"published": "2025-07-11T17:02:06.063924Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-11T17:02:06.063944Z",
"modified": "2025-07-11T17:02:06.082048Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 1127311,
"topic": "gcn.circulars",
"uuid": "82ed53ea-97aa-4dbd-b786-72dd41f2fc77",
"title": "EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes",
"submitter": "David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>",
"authors": "David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41067"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.41067....1P",
"eventId": "EP250702a",
"subject": "EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes",
"createdOn": 1752253316463,
"submitter": "David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>",
"circularId": 41067,
"submittedHow": "web"
},
"message_text": "D. Paneque (MPP Munich), M. Teshima (MPP Munich), Arnau Aguasca-Cabot (UB, ICCUB, and IEEC-UB), Alessio Berti (MPP Munich), Sweta Menon (UNIROMA2 & INAF), Edna Ruiz-Velasco (LAPP Annecy), Monica Seglar-Arroyo (IFAE Barcelona) and Andrea Simongini (UNIROMA2 & INAF), on behalf of the CTAO-LST and MAGIC Collaborations report:\n\nWe observed the field of EP250702a / GRBs 250702B,D,E (GCN 40883, 40886, 40890, 40891, 40906). A total of 2.94 hours of observations were conducted with the MAGIC telescopes, beginning at 2025-07-04 01:25:53 UTC. The final 1.79 hours of this period were carried out jointly with LST-1. \n\nA preliminary offline analysis of the LST-1 and MAGIC dataset shows no excess of gamma rays above 200 GeV in the field of EP250702a (GCN 40906). These results have been obtained using the LST analysis software, lst-chain (LST Collaboration, 2023 ApJ 956 80, v0.10.7), and the MAGIC analysis software MARS (Zanin et al. 2013, v 3.2.1). Observations were affected by reduced atmospheric transparency. A more in-depth analysis of this data set is ongoing.\n\nSubsequent observations are planned after the moonbreak, subject to the nature of upcoming detections.\n\nLST-1 is a prototype of the Large-Sized Telescope (LST) for the Cherenkov Telescope Array Observatory, and is located on the Canary island of La Palma, Spain. The telescope design is optimized for observation of gamma rays in the range from 20 GeV to 3 TeV.\n\nMAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV.\n",
"published": "2025-07-21T09:51:09.091048Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-21T09:51:09.091069Z",
"modified": "2025-07-21T09:51:09.096339Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 350646,
"topic": "gcn.circulars",
"uuid": "374babc8-b413-44ab-9bb5-a8ad2ff875dd",
"title": "EP250702a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40912"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a: Global MASTER-Net observations report",
"createdOn": 1751540970929,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40912,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250702a ( EP Team et al., GCN 40906) errorbox 1 days 2370 sec after trigger time at 2025-07-03 03:33:14 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 29 deg. The sun altitude is -73.4 deg. \n\nThe galactic latitude b = -6 deg., longitude l = 27 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2923840\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 88860 | 2025-07-03 03:33:14 | MASTER-OAFA | (18h 57m 22.01s , -08d 01m 07.7s) | C | 180 | 17.4 | \n 89047 | 2025-07-03 03:36:20 | MASTER-OAFA | (18h 57m 21.64s , -08d 01m 10.1s) | C | 180 | 17.3 | \n 89233 | 2025-07-03 03:39:27 | MASTER-OAFA | (18h 57m 21.26s , -08d 01m 13.3s) | C | 180 | 17.4 | \n 89419 | 2025-07-03 03:42:32 | MASTER-OAFA | (18h 57m 20.88s , -08d 01m 16.3s) | C | 180 | 17.3 | \n 104587 | 2025-07-03 07:56:21 | MASTER-OAFA | (18h 58m 32.22s , -07d 41m 30.2s) | C | 60 | 17.4 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-07-03T11:09:40.145271Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-03T11:09:40.145291Z",
"modified": "2025-07-03T11:09:40.158086Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421067,
"topic": "gcn.circulars",
"uuid": "8f4ed6eb-7c00-4d77-b178-7b628a4d9444",
"title": "EP250702a: Global MASTER-Net observations report",
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40912"
},
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40912....1L",
"eventId": "EP250702a",
"subject": "EP250702a: Global MASTER-Net observations report",
"createdOn": 1751540970929,
"submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"circularId": 40912,
"submittedHow": "email"
},
"message_text": "V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, \nG.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),\nO.Gress, N.Budnev (ISU),\nC.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA.Sosnovskij (CrAO),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),\nD.Buckley (SAAO),\nR.Rebolo (The Instituto de Astrofisica de Canarias),\nL.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,\nA.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) \n\nMASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250702a ( EP Team et al., GCN 40906) errorbox 1 days 2370 sec after trigger time at 2025-07-03 03:33:14 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 29 deg. The sun altitude is -73.4 deg. \n\nThe galactic latitude b = -6 deg., longitude l = 27 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=2923840\n\nWe obtain a following upper limits. \n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 88860 | 2025-07-03 03:33:14 | MASTER-OAFA | (18h 57m 22.01s , -08d 01m 07.7s) | C | 180 | 17.4 | \n 89047 | 2025-07-03 03:36:20 | MASTER-OAFA | (18h 57m 21.64s , -08d 01m 10.1s) | C | 180 | 17.3 | \n 89233 | 2025-07-03 03:39:27 | MASTER-OAFA | (18h 57m 21.26s , -08d 01m 13.3s) | C | 180 | 17.4 | \n 89419 | 2025-07-03 03:42:32 | MASTER-OAFA | (18h 57m 20.88s , -08d 01m 16.3s) | C | 180 | 17.3 | \n 104587 | 2025-07-03 07:56:21 | MASTER-OAFA | (18h 58m 32.22s , -07d 41m 30.2s) | C | 60 | 17.4 | \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.\n",
"published": "2025-07-14T08:07:57.072256Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:07:57.072269Z",
"modified": "2025-07-14T08:07:57.075536Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 366693,
"topic": "gcn.circulars",
"uuid": "5c08354d-961c-4511-a3b0-75c6aced811f",
"title": "EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST",
"submitter": "akashjanaki98@gmail.com",
"authors": "akashjanaki98@gmail.com",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40983"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST",
"createdOn": 1751754372854,
"submitter": "akashjanaki98@gmail.com",
"circularId": 40983,
"submittedHow": "web"
},
"message_text": "Akash Anumarlapudi (UNC Chapel Hill), David Kaplan (UWM), Igor Andreoni (UNC Chapel Hill), Dougal Dobie (U. Sydney/OzGrav), Tara Murphy (U. Sydney) on behalf of the VAST collaboration.\n\nFermi Gamma-ray Burst Monitor (GBM) reported the discovery of four possible long-durational GRBs, GRB 250702B,C,D,E, that might likely be coming from the same source (GCN #40891). Further X-ray observations by the Einstein Probe (EP; GCN #40906), MAXI (GCN #40910), Konus-WIND (GCN #40914), and SVOM (GCN #40923) resulted in the discovery of an X-ray counterpart. Data from the Wide-field X-ray Telescope (WXT) aboard EP revealed that the source was active in X-rays even a day before the Fermi GBM discovery. Follow-up observations from the Follow-up X-ray Telescope on EP (FXT, GCN #40906) constrained the position of the source to 20 arcseconds (90% confidence). No optical counterparts were reported down to i=22.0 (GCN #40918), but infrared observations have resulted in the discovery of a candidate counterpart (GCN #40924) with Ks~17.3 Vega, which is very red in color and rapidly fading (GCN #40961). Subsequent analysis of GBM data suggested that the burst GRB 250702C is likely not related to GRB 250702 B/D/E, but an unrelated short GRB (GCN #40931).\n\nHere we report the archival radio observations of this source taken at the Australian SKA Pathfinder (ASKAP) observations as part of the Variable And Slow Transients Survey (VAST; Murphy et al. 2021) at 887.5 MHz.\n\nThe position of the source was observed for 13 epochs, roughly with a two-week cadence between March 2024 and December 2024. Each observation lasted approximately 12 minutes, reaching a sensitivity (noise level) of 250 uJy. The source was not detected in any of the single-epoch images. We stacked the individual exposures, which also resulted in a non-detection. The 1-sigma noise level at the location of the source is 75 uJy, and hence we place a limit on the persistent radio flux density (5-sigma) of the source to be < 375 uJy.",
"published": "2025-07-05T22:26:19.884089Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-05T22:26:19.884105Z",
"modified": "2025-07-05T22:26:19.890164Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421291,
"topic": "gcn.circulars",
"uuid": "d7f735b8-fb23-4635-95b1-83d01762ec47",
"title": "EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST",
"submitter": "akashjanaki98@gmail.com",
"authors": "akashjanaki98@gmail.com",
"data": {
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"gcn_circular": "https://gcn.nasa.gov/circulars/40983"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40983....1A",
"eventId": "EP250702a",
"subject": "EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST",
"createdOn": 1751754372854,
"submitter": "akashjanaki98@gmail.com",
"circularId": 40983,
"submittedHow": "web"
},
"message_text": "Akash Anumarlapudi (UNC Chapel Hill), David Kaplan (UWM), Igor Andreoni (UNC Chapel Hill), Dougal Dobie (U. Sydney/OzGrav), Tara Murphy (U. Sydney) on behalf of the VAST collaboration.\n\nFermi Gamma-ray Burst Monitor (GBM) reported the discovery of four possible long-durational GRBs, GRB 250702B,C,D,E, that might likely be coming from the same source (GCN #40891). Further X-ray observations by the Einstein Probe (EP; GCN #40906), MAXI (GCN #40910), Konus-WIND (GCN #40914), and SVOM (GCN #40923) resulted in the discovery of an X-ray counterpart. Data from the Wide-field X-ray Telescope (WXT) aboard EP revealed that the source was active in X-rays even a day before the Fermi GBM discovery. Follow-up observations from the Follow-up X-ray Telescope on EP (FXT, GCN #40906) constrained the position of the source to 20 arcseconds (90% confidence). No optical counterparts were reported down to i=22.0 (GCN #40918), but infrared observations have resulted in the discovery of a candidate counterpart (GCN #40924) with Ks~17.3 Vega, which is very red in color and rapidly fading (GCN #40961). Subsequent analysis of GBM data suggested that the burst GRB 250702C is likely not related to GRB 250702 B/D/E, but an unrelated short GRB (GCN #40931).\n\nHere we report the archival radio observations of this source taken at the Australian SKA Pathfinder (ASKAP) observations as part of the Variable And Slow Transients Survey (VAST; Murphy et al. 2021) at 887.5 MHz.\n\nThe position of the source was observed for 13 epochs, roughly with a two-week cadence between March 2024 and December 2024. Each observation lasted approximately 12 minutes, reaching a sensitivity (noise level) of 250 uJy. The source was not detected in any of the single-epoch images. We stacked the individual exposures, which also resulted in a non-detection. The 1-sigma noise level at the location of the source is 75 uJy, and hence we place a limit on the persistent radio flux density (5-sigma) of the source to be < 375 uJy.",
"published": "2025-07-14T08:08:46.641757Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:46.641770Z",
"modified": "2025-07-14T08:08:46.644982Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421047,
"topic": "gcn.circulars",
"uuid": "1375a4ab-09cb-4c11-a51d-be5247f3d89c",
"title": "EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40917"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40917....1C",
"eventId": "EP250702a",
"subject": "EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation",
"createdOn": 1751555129881,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40917,
"submittedHow": "web"
},
"message_text": " \nH. Q. Cheng (NAO, CAS), Y. J. Zhang (THU), G. Y. Zhao (SYSU), C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), Y. L. Wang (NAO, CAS; ICE, CSIC-IEEC), F. Coti Zelati, A. Marino, N. Rea (ICE, CSIC-IEEC), J. W. Hu, H. Sun, Z. X. Ling, W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team: \n \nFollowing the detection of GRB 250702B, C, D, E by Fermi/GBM (GCN 40883, 40885, 40886, 40890, 40891) and its likely X-ray counterpart EP250702a detected by Einstein Probe (EP, GCN 40906, ATel #17261), MAXI (GCN 40910) and Konus-Wind (GCN 40914), we performed a follow-up observation on EP250702a with the Follow-up X-ray Telescope (FXT) onboard EP. The observation began at 2025-07-03T02:44:11, with an exposure of about 3875 s. \n \nOur on-ground analysis showed that an X-ray source is detected at R.A.= 284.6895 deg, Dec= -7.8738 deg, with an uncertainty of 10 arcsecond (90% C.L. systematic and statistical), which is within the error circle of the EP-WXT position of EP250702a. Considering the possibility of the source being a Galactic object and given the improved source localization, we also designate the source EP J185845.5-075225. The FXT spectrum can be fitted with an absorped power law model, yielding a column density of (7.9+/-0.6)e21 cm^-2, a photon index of 1.57+/-0.07, and an unabsorbed 0.5-10 keV flux of (5.52+/-0.21)e-11 erg/s/cm^2. We also performed preliminary timing analysis using the FXT data collected so far, and no significant periodic or quasi-periodic signals were detected.\n \nEP-FXT will continue to monitor this source in the next days. The contact transient advocates of this source are Huaqing Cheng (hqcheng@nao.cas.cn) and Yi-Jia Zhang (zhangyij21@mails.tsinghua.edu.cn) Please contact them for coordination of multi-wavelength follow-up observations. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. ",
"published": "2025-07-14T08:07:55.830732Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:07:55.830744Z",
"modified": "2025-07-14T08:07:55.834069Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 351702,
"topic": "gcn.circulars",
"uuid": "c447e0d5-7a49-40c8-acd4-ab5ccf9b838e",
"title": "EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40917"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation",
"createdOn": 1751555129881,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40917,
"submittedHow": "web"
},
"message_text": " \nH. Q. Cheng (NAO, CAS), Y. J. Zhang (THU), G. Y. Zhao (SYSU), C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), Y. L. Wang (NAO, CAS; ICE, CSIC-IEEC), F. Coti Zelati, A. Marino, N. Rea (ICE, CSIC-IEEC), J. W. Hu, H. Sun, Z. X. Ling, W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team: \n \nFollowing the detection of GRB 250702B, C, D, E by Fermi/GBM (GCN 40883, 40885, 40886, 40890, 40891) and its likely X-ray counterpart EP250702a detected by Einstein Probe (EP, GCN 40906, ATel #17261), MAXI (GCN 40910) and Konus-Wind (GCN 40914), we performed a follow-up observation on EP250702a with the Follow-up X-ray Telescope (FXT) onboard EP. The observation began at 2025-07-03T02:44:11, with an exposure of about 3875 s. \n \nOur on-ground analysis showed that an X-ray source is detected at R.A.= 284.6895 deg, Dec= -7.8738 deg, with an uncertainty of 10 arcsecond (90% C.L. systematic and statistical), which is within the error circle of the EP-WXT position of EP250702a. Considering the possibility of the source being a Galactic object and given the improved source localization, we also designate the source EP J185845.5-075225. The FXT spectrum can be fitted with an absorped power law model, yielding a column density of (7.9+/-0.6)e21 cm^-2, a photon index of 1.57+/-0.07, and an unabsorbed 0.5-10 keV flux of (5.52+/-0.21)e-11 erg/s/cm^2. We also performed preliminary timing analysis using the FXT data collected so far, and no significant periodic or quasi-periodic signals were detected.\n \nEP-FXT will continue to monitor this source in the next days. The contact transient advocates of this source are Huaqing Cheng (hqcheng@nao.cas.cn) and Yi-Jia Zhang (zhangyij21@mails.tsinghua.edu.cn) Please contact them for coordination of multi-wavelength follow-up observations. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. ",
"published": "2025-07-03T15:05:37.662635Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-03T15:05:37.662665Z",
"modified": "2025-07-03T15:05:37.666413Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 349698,
"topic": "gcn.circulars",
"uuid": "0109139c-98f7-4592-965f-33ba8f5a8b99",
"title": "EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits",
"submitter": "Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>",
"authors": "Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40908"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits",
"createdOn": 1751528307179,
"submitter": "Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>",
"circularId": 40908,
"submittedHow": "web"
},
"message_text": "A. Kumar, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. O'Neill, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:\n\nWe report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250702B, C, D and E (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890 and 40891). Targeted observations were performed between 2025-07-02 23:16:56 UT and 2025-07-03 02:52:31 UT (between 20.39 and 23.98 hours after trigger). Each observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).\n\nImages were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. Human vetting was carried out in real time on any candidates that passed the above checks.\n\nWe identify no candidate optical counterparts within the EP/FXT (Cheng et al. 40906) 90% localisation region with typical 3-sigma limits ranging between L > 19.85 to L > 20.35 (AB). The deepest of these was taken at a mid-time of 2025-07-03 02:06:10 UT (23.21 hours after trigger).\n\nMagnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.\n\n(https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).\n",
"published": "2025-07-03T07:38:35.308873Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-03T07:38:35.308888Z",
"modified": "2025-07-03T07:38:35.314631Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421166,
"topic": "gcn.circulars",
"uuid": "35c8b2ec-3524-4e25-ba37-546cb8445be3",
"title": "EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits",
"submitter": "Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>",
"authors": "Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40908"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40908....1K",
"eventId": "EP250702a",
"subject": "EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits",
"createdOn": 1751528307179,
"submitter": "Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>",
"circularId": 40908,
"submittedHow": "web"
},
"message_text": "A. Kumar, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. O'Neill, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:\n\nWe report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250702B, C, D and E (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890 and 40891). Targeted observations were performed between 2025-07-02 23:16:56 UT and 2025-07-03 02:52:31 UT (between 20.39 and 23.98 hours after trigger). Each observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).\n\nImages were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. Human vetting was carried out in real time on any candidates that passed the above checks.\n\nWe identify no candidate optical counterparts within the EP/FXT (Cheng et al. 40906) 90% localisation region with typical 3-sigma limits ranging between L > 19.85 to L > 20.35 (AB). The deepest of these was taken at a mid-time of 2025-07-03 02:06:10 UT (23.21 hours after trigger).\n\nMagnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.\n\n(https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).\n",
"published": "2025-07-14T08:08:38.353124Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:38.353136Z",
"modified": "2025-07-14T08:08:38.356372Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 378951,
"topic": "gcn.circulars",
"uuid": "9d975f77-4a20-4012-b0fb-92819bec42db",
"title": "EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit",
"submitter": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"authors": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41016"
},
"format": "text/markdown",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit",
"createdOn": 1751915892723,
"submitter": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"circularId": 41016,
"submittedHow": "web"
},
"message_text": "D. Akl (AUS), K. Noysena, A. Manasanun (NARIT), M. Freeberg, R. Hellot (KNC), C. Andrade (UMN), W. Corradi (LNA), M. Pillas (Uliege), S. Antier (OCA/IJCLAB), N. Kochiashvili (AbAO), M. Lamoureux (UCLouvain), on behalf of GRANDMA:\n\nWe observed the field of EP250702a (GCN 40906; associated with GRBs 250702/B/D/E) with GRANDMA and Kilonova Catcher and did not detect any optical counterpart.\n\nAll our measurements can be downloaded from: [https://skyportal-icare.ijclab.in2p3.fr/public/sources/EP250702a/](https://skyportal-icare.ijclab.in2p3.fr/public/sources/EP250702a/version/6fb8f8a859cfe4cfa365649da544d81d)\n\nAll the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousin filters were calibrated using the Gaia DR3 Synphot catalog.\n\nWe use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).\n\nOur observations are consistent with previously reported measurements (refer to SkyPortal for a subset of GCN measurements we collected).\n\nGRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/)",
"published": "2025-07-07T19:18:21.086805Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-07T19:18:21.086827Z",
"modified": "2025-07-07T19:18:21.091438Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421222,
"topic": "gcn.circulars",
"uuid": "18b0d4a3-3b3a-4aa5-bffd-032488b58e99",
"title": "EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit",
"submitter": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"authors": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41016"
},
"format": "text/markdown",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.41016....1A",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit",
"createdOn": 1751915892723,
"submitter": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"circularId": 41016,
"submittedHow": "web"
},
"message_text": "D. Akl (AUS), K. Noysena, A. Manasanun (NARIT), M. Freeberg, R. Hellot (KNC), C. Andrade (UMN), W. Corradi (LNA), M. Pillas (Uliege), S. Antier (OCA/IJCLAB), N. Kochiashvili (AbAO), M. Lamoureux (UCLouvain), on behalf of GRANDMA:\n\nWe observed the field of EP250702a (GCN 40906; associated with GRBs 250702/B/D/E) with GRANDMA and Kilonova Catcher and did not detect any optical counterpart.\n\nAll our measurements can be downloaded from: [https://skyportal-icare.ijclab.in2p3.fr/public/sources/EP250702a/](https://skyportal-icare.ijclab.in2p3.fr/public/sources/EP250702a/version/6fb8f8a859cfe4cfa365649da544d81d)\n\nAll the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousin filters were calibrated using the Gaia DR3 Synphot catalog.\n\nWe use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).\n\nOur observations are consistent with previously reported measurements (refer to SkyPortal for a subset of GCN measurements we collected).\n\nGRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/)",
"published": "2025-07-14T08:08:40.902956Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:40.902969Z",
"modified": "2025-07-14T08:08:40.905990Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 1121555,
"topic": "gcn.circulars",
"uuid": "0d9aea0e-2e7a-464d-ab28-48eaf0ca629b",
"title": "EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations ",
"submitter": "Andrew Levan at Radboud University <a.levan@astro.ru.nl>",
"authors": "Andrew Levan at Radboud University <a.levan@astro.ru.nl>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41096"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.41096....1G",
"eventId": "EP250702a",
"subject": "EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations ",
"createdOn": 1752583690254,
"submitter": "Andrew Levan at Radboud University <a.levan@astro.ru.nl>",
"circularId": 41096,
"submittedHow": "web"
},
"message_text": "EP250702a / GRB 250702BD,D,E: Hubble Space Telescope Observations \n\nA. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Saccardi (CEA/Irfu), P. O’Brien (Univ. of Leicester), R. A. J. Eyles-Ferris (Univ. of Leicester), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), S. D. Vergani (LUX-Paris Obs.), N. R. Tanvir (U. Leicester), B. P. Gompertz (U. Birmingham) report for the Stargate collaboration: \n\nWe observed the location of EP250702a / GRB 250702B,D,E (Cheng et al., GCNs 40906, 40917; Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914) with the Hubble Space Telescope on 15 July 2025. A total of 2196 s of observations were obtained using WFC3 and the F160W (broad-band H) filter. \n\n\nAt the location of the infrared counterpart (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961) we clearly resolve a galaxy, whose nucleus is offset 0.7” from the transient location. The galaxy has an edge-on morphology, and either a disturbed disc or prominent dust lane. The transient lies on the stellar field of this galaxy, and the low probability of chance alignment (0.05%: Levan et al., GCN 40961) strongly implies that EP250702a / GRB 250702BDE is indeed an extragalactic transient. A weak excess of emission over the smooth disc is present at the transient location, but it appears likely the flux is now dominated by galaxy light. \n\nIf extragalactic in origin the very long duration of the outburst is extremely unusual. Only relativistic TDEs have been seen to have such long-lived emission in gamma-rays. However, the non-nuclear nature of the transient is not in keeping with the expected location of a supermassive black hole, although is consistent with the expectations for white-dwarf - intermediate mass black hole disruptions.\n\nWe thank Bill Januszewski, Joel Green, Claus Leitherer and Jennifer Lotz for their rapid work in approving and scheduling these observations. \n",
"published": "2025-07-21T09:50:06.186697Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-21T09:50:06.186710Z",
"modified": "2025-07-21T09:50:06.191681Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 429159,
"topic": "gcn.circulars",
"uuid": "5476ad6b-7c36-4d20-a70b-522480d0aa95",
"title": "EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations ",
"submitter": "Andrew Levan at Radboud University <a.levan@astro.ru.nl>",
"authors": "Andrew Levan at Radboud University <a.levan@astro.ru.nl>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41096"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations ",
"createdOn": 1752583690254,
"submitter": "Andrew Levan at Radboud University <a.levan@astro.ru.nl>",
"circularId": 41096,
"submittedHow": "web"
},
"message_text": "EP250702a / GRB 250702BD,D,E: Hubble Space Telescope Observations \n\nA. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Saccardi (CEA/Irfu), P. O’Brien (Univ. of Leicester), R. A. J. Eyles-Ferris (Univ. of Leicester), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), S. D. Vergani (LUX-Paris Obs.), N. R. Tanvir (U. Leicester), B. P. Gompertz (U. Birmingham) report for the Stargate collaboration: \n\nWe observed the location of EP250702a / GRB 250702B,D,E (Cheng et al., GCNs 40906, 40917; Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914) with the Hubble Space Telescope on 15 July 2025. A total of 2196 s of observations were obtained using WFC3 and the F160W (broad-band H) filter. \n\n\nAt the location of the infrared counterpart (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961) we clearly resolve a galaxy, whose nucleus is offset 0.7” from the transient location. The galaxy has an edge-on morphology, and either a disturbed disc or prominent dust lane. The transient lies on the stellar field of this galaxy, and the low probability of chance alignment (0.05%: Levan et al., GCN 40961) strongly implies that EP250702a / GRB 250702BDE is indeed an extragalactic transient. A weak excess of emission over the smooth disc is present at the transient location, but it appears likely the flux is now dominated by galaxy light. \n\nIf extragalactic in origin the very long duration of the outburst is extremely unusual. Only relativistic TDEs have been seen to have such long-lived emission in gamma-rays. However, the non-nuclear nature of the transient is not in keeping with the expected location of a supermassive black hole, although is consistent with the expectations for white-dwarf - intermediate mass black hole disruptions.\n\nWe thank Bill Januszewski, Joel Green, Claus Leitherer and Jennifer Lotz for their rapid work in approving and scheduling these observations. \n",
"published": "2025-07-15T12:48:17.995141Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-15T12:48:17.995159Z",
"modified": "2025-07-15T12:48:18.007951Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 1193137,
"topic": "gcn.circulars",
"uuid": "1158104d-a116-4756-9cd2-4fa64ed7d85d",
"title": "EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41122"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit",
"version": 2,
"editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"editedOn": 1753114223188,
"createdOn": 1752938496346,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 41122,
"submittedHow": "web"
},
"message_text": "H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM mission team.\n\nSVOM/VT conducted two ToO follow-up observations of EP250702a (Cheng et al., GCNs 40906, 40917), which was likely associated with the long burst GRB250702B,D,E (Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914; Wang et al., GCN 40923). \n\nThe first observation was made on July 3, 2025 in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, between 10:54:08 and 15:10:00 (UTC), 32.0 to 36.3 hours after the EP/WXT trigger (Cheng et al., GCN 40906). The second one was made on July 5, 2025, between 08:56:18 and 15:41:13, 3.25 days to 3.53 days after the EP/WXT trigger (Cheng et al., GCN 40906).\n\nThe counterpart detected by VLT (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961), MOSFIRE (Sharma et al., GCN 41044), HST (Levan et al., GCN 41096), MeerKAT (Bright et al., GCN 40985), VLA (Sfaradi et al., GCN 41053) and ALMA (Alexander et al., GCN 41059) was not detected in our images for both observations. \n\nThe 3 sigma upper limit magnitudes were estimated:\n Mid-time | Exposure time | Band | upper limit (AB)\n 34.2 hours | 80*100 sec | VT_R | 23.6 mag\n 34.2 hours | 81*100 sec | VT_B | 23.8 mag\n 3.53 days | 81*100 sec | VT_R | 23.6 mag\n 3.53 days | 81*100 sec | VT_B | 23.8 mag\n\nThe Mid-time above is the relative time from the trigger time of EP/WXT (Cheng et al., GCN 40906).\n\nThe result is consistent with the optical upper limit from GOTO (Kumar et al., GCN 40908), MASTER (Lipunov et al., GCN 40912), Colibri (Becerra et al., GCN 40918), CAHA (Pérez-García et al., GCN 40929), WFST (Hua et al., GCN 40943), FTW (Busmann et al., GCN 40949), UVOT (Siegel et al., GCN 40952), SYSU (Li et al., GCN 40986) and GRANDMA(Akl et al., GCN 41016).\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.",
"published": "2025-07-21T18:04:24.682072Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-21T18:04:24.682097Z",
"modified": "2025-07-21T18:04:24.687379Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 763344,
"topic": "gcn.circulars",
"uuid": "07db2c06-96e6-4887-b6ed-3258b89855a8",
"title": "EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit",
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"authors": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41122"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit",
"createdOn": 1752938496346,
"submitter": "Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>",
"circularId": 41122,
"submittedHow": "web"
},
"message_text": "H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM mission team.\n\nSVOM/VT conducted two ToO follow-up observations of EP250702a (Cheng et al., GCNs 40906, 40917), which was likely associated with the long burst GRB250702B,D,E (Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914; Wang et al., GCN 40923). \n\nThe first observation was made on July 3, 2025 in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, between 10:54:08 and 15:10:00 (UTC), 32.0 to 36.3 hours after the EP/WXT trigger (Cheng et al., GCN 40906). The second one was made on July 5, 2025, between 08:56:18 and 15:41:13, 3.25 days to 3.53 days after the EP/WXT trigger (Cheng et al., GCN 40906).\n\nThe counterpart detected by VLT (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961), MOSFIRE (Sharma et al., GCN 41044), HST (Levan et al., GCN 41096), MeerKAT (Bright et al., GCN 40985), VLA (Sfaradi et al., GCN 41053) and ALMA (Alexander et al., GCN 41059) was not detected in our images for both observations. \n\nThe 3 sigma upper limit magnitudes were estimated:\n Mid-time | Exposure time | Band | upper limit (AB)\n 34.2 hours | 80*100 sec | VT_R | 23.6\n 34.2 hours | 81*100 sec | VT_B | 23.8\n 3.53 days | 81*100 sec | VT_R | 23.6\n 3.53 days | 81*100 sec | VT_B | 23.8\n\nThe Mid-time above is the relative time from the trigger time of EP/WXT (Cheng et al., GCN 40906).\n\nThe result is consistent with the optical upper limit from GOTO (Kumar et al., GCN 40908), MASTER (Lipunov et al., GCN 40912), Colibri (Becerra et al., GCN 40918), CAHA (Pérez-García et al., GCN 40929), WFST (Hua et al., GCN 40943), FTW (Busmann et al., GCN 40949), UVOT (Siegel et al., GCN 40952), SYSU (Li et al., GCN 40986) and GRANDMA(Akl et al., GCN 41016).\n\nThe Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.",
"published": "2025-07-19T15:21:45.262331Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-19T15:21:45.262345Z",
"modified": "2025-07-19T15:21:45.270595Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 1668244,
"topic": "gcn.circulars",
"uuid": "8eb03a35-0f1d-4b2d-8af8-6585848fca4a",
"title": "EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz",
"submitter": "Arvind Balasubramanian <arvind6895@gmail.com>",
"authors": "Arvind Balasubramanian <arvind6895@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41145"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz",
"createdOn": 1753337597057,
"submitter": "Arvind Balasubramanian <arvind6895@gmail.com>",
"circularId": 41145,
"submittedHow": "web"
},
"message_text": "A. Balasubramanian (IIA), L. Resmi (IIST), D. Eappachen (IIA), S K Jagan (IIST), V. Bhalerao (IITB), B. Zhang (HKU), G.C. Anupama (IIA), H Sun (NAO, CAS), D. K. Sahu (IIA), and W. Yuan (NAO, CAS) report:\n\nWe observed the field of the X-ray transient EP250702a/GRB250702 B,D,E (GCNs 40906, 40883, 40886, 40890, 40891) with upgraded Giant Metrewave Radio Telescope under the joint uGMRT ToO proposals 48_059 (PI: D. Eappachen) and 48_167 (PI: L. Resmi) on 12th July 2025 in band 5 (1.26 GHz) for a total of 4 hours starting from 19:30 UTC. \n\nIn our preliminary analysis, we detect a point source with a flux density of ~90 uJy at the position of EP250702a. We used 3C48 for the flux calibration and J1911+201 for complex gain and phase calibration. The CAPTURE-CASA6 pipeline was used for data calibration and imaging. \n\nWe thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.\n",
"published": "2025-07-24T06:13:25.726581Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-24T06:13:25.726596Z",
"modified": "2025-07-24T06:13:25.732347Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 366928,
"topic": "gcn.circulars",
"uuid": "a0f45b7c-423d-44f1-a7e2-e2849e568bf0",
"title": "EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart",
"submitter": "Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>",
"authors": "Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40985"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart",
"createdOn": 1751757495877,
"submitter": "Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>",
"circularId": 40985,
"submittedHow": "web"
},
"message_text": "Authors: J. Bright (Oxford), F. Carotenuto (INAF, Rome), P. G. Jonker (Radboud), on behalf of a larger collaboration\n\nWe observed the field of EP250702a (GCN 40906; associated with GRBs 250702/B/D/E) with the MeerKAT radio telescope from 2025-07-04 17:37:32 UTC to 2025-07-04 18:39:55 UTC (with a total time on source of 44 minutes) using the S band receiver at a central frequency of 3.06 GHz. Analysing the SARAO Science Data Processor output continuum image we detect a source at the position of EP250702a with a flux density of around 100uJy/beam, with a typical image noise of around 8uJy/beam. Our detection is consistent with the upper limit reported by the Allen Telescope Array (GCN 40979).\n\nUnder the assumption of a source distance of 10 kpc we infer a radio luminosity of around 3.5e28 erg/s, consistent with X-ray binaries during the less luminous phases of their outburst cycles. The extragalactic/galactic nature of EP250702a is therefore not clarified by these observations.\n\nFurther observations will be conducted to check for variability. \n\nWe thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the \"MPIfR S-band receiver system\" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society.\n",
"published": "2025-07-05T23:18:24.899138Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-05T23:18:24.899154Z",
"modified": "2025-07-05T23:18:24.903426Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421078,
"topic": "gcn.circulars",
"uuid": "7db911c9-7c2d-4445-b104-526112c03edb",
"title": "EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart",
"submitter": "Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>",
"authors": "Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40985"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40985....1B",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart",
"createdOn": 1751757495877,
"submitter": "Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>",
"circularId": 40985,
"submittedHow": "web"
},
"message_text": "Authors: J. Bright (Oxford), F. Carotenuto (INAF, Rome), P. G. Jonker (Radboud), on behalf of a larger collaboration\n\nWe observed the field of EP250702a (GCN 40906; associated with GRBs 250702/B/D/E) with the MeerKAT radio telescope from 2025-07-04 17:37:32 UTC to 2025-07-04 18:39:55 UTC (with a total time on source of 44 minutes) using the S band receiver at a central frequency of 3.06 GHz. Analysing the SARAO Science Data Processor output continuum image we detect a source at the position of EP250702a with a flux density of around 100uJy/beam, with a typical image noise of around 8uJy/beam. Our detection is consistent with the upper limit reported by the Allen Telescope Array (GCN 40979).\n\nUnder the assumption of a source distance of 10 kpc we infer a radio luminosity of around 3.5e28 erg/s, consistent with X-ray binaries during the less luminous phases of their outburst cycles. The extragalactic/galactic nature of EP250702a is therefore not clarified by these observations.\n\nFurther observations will be conducted to check for variability. \n\nWe thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the \"MPIfR S-band receiver system\" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society.\n",
"published": "2025-07-14T08:07:57.174629Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:07:57.174641Z",
"modified": "2025-07-14T08:07:57.178030Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 1784178,
"topic": "gcn.circulars",
"uuid": "5e7367ad-8761-499d-a132-ad3a120c1a4e",
"title": "EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz",
"submitter": "stephane.corbel@cea.fr",
"authors": "stephane.corbel@cea.fr",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41147"
},
"format": "text/markdown",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz",
"createdOn": 1753378041849,
"submitter": "stephane.corbel@cea.fr",
"circularId": 41147,
"submittedHow": "web"
},
"message_text": "Author: N. Grollimund, S. Corbel (Univ. Paris Cité & CEA Saclay), A. Coleiro, F. Cangemi (Univ. Paris Cité), J. Rodriguez (CEA Saclay) on behalf of a larger team. \n\nWe observed the field of EP250702a (GCN 40906) with the MeerKAT radio telescope (proposal ID MKT-24172; PI: Corbel) using the S-band receivers, at a central frequency of 3.06 GHz. We conducted our observations from 2025-07-21 23:34:37 UTC, with a total on-source time of 11 min. We used J1939-6342 for flux and bandpass calibration, and J1822-0938 for complex gain calibration.\n\nWe detect a point source with a flux density of 147 +/- 19 uJy at the position of EP250702a, with an RMS noise level of ~15 uJy/beam. Our observation, in combination with the detection of a ~100 uJy point source reported in GCN 40985, implies that the flux of EP250702a increased by ~50% at 3 GHz between 2025-07-04 and 2025-07-21.\n\nAveraging the fitted positions from all of our S-band observations, we find a refined radio position for the source: R.A. = 18:58:45.549 +/- 0.01s, Dec. = -7:52:26.54 +/- 0.15’'. This position is consistent with the radio position reported by VLA in GCN 41053, as well as the NIR and X-ray counterparts (GCNs 40924, 40906).\n\nFurther observations are planned.\n\nWe thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the \"MPIfR S-band receiver system\" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society.\n",
"published": "2025-07-24T18:18:47.727194Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-24T18:18:47.727210Z",
"modified": "2025-07-24T18:18:47.814668Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 378543,
"topic": "gcn.circulars",
"uuid": "a6050a9f-95e6-4c37-a9b7-7b4fda7f8982",
"title": "EP250702a/ GRB 250702B: NuSTAR X-ray Observations",
"submitter": "Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>",
"authors": "Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41014"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a/ GRB 250702B: NuSTAR X-ray Observations",
"createdOn": 1751910406231,
"submitter": "Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>",
"circularId": 41014,
"submittedHow": "web"
},
"message_text": "Brendan O’Connor (CMU), Dheeraj Pasham (Eureka Scientific/George Washington), Igor Andreoni (UNC), Jeremy Hare (Catholic/GSFC) report on behalf of a larger collaboration:\n\nWe observed the X-ray transient EP250702a (GCN 40906), which is also associated with the multiple gamma-ray triggers designated as GRB 250702B/D/E (GCNs 40883, 40886, 40890, 40891, 40931, 40903, 40914, 40923), with the NuSTAR X-ray Telescope through a Target of Opportunity observation through GO program 11282 (PI: Pasham). The observation occurred between 2025-07-03 20:45:21 and 2025-07-04 09:15:00 UTC for an on-source exposure of ~21.5 ks, simultaneous with Swift/XRT observations (ObsID: 19906002). \n\nThe source is clearly detected at an average rate of ~0.4 cts/s. The 3-79 keV X-ray lightcurve shows short term variability throughout the full exposure in both FPMA and FPMB, but no flaring is observed. The source varies in count rate by a factor of 2-3 on timescales as short as a few ks. Compared to NuSTAR observations of GRB 221009A at a similar count rate (GCNs 32695, 32788), the source shows more significant variability, which we suggest disfavors an ultralong GRB origin, especially in conjunction with the July 1st onset reported by the Einstein Probe (GCN 40906). \n\nThe X-ray spectra are featureless and do not show any Fe lines or reflection features. This is consistent with the lack of features in the Swift/XRT spectra. The 3-79 keV spectrum (FPMA+FPMB) is well fit by an absorbed powerlaw with a photon index of Gamma~1.81+/-0.03, which is consistent with the initial Swift/XRT spectral index within errors (GCN 40919). The hydrogen column density was fixed to 1e22 cm^-2 as per the best-fit Swift/XRT spectra (see https://www.swift.ac.uk/LSXPS/transients/9377) The unabsorbed 3-79 keV flux (time-averaged) is (2.35+/-0.05)e-11 erg/cm^2/s during our observation. \n\nWe also performed a fit with an absorbed cutoff powerlaw and find a cutoff energy >60 keV. In this case, the best-fit photon index is Gamma~1.67+/-0.08. This has better agreement with the EP/FXT result, although the FXT observation was obtained at an earlier time (GCN 40917). The C-stat between both fits to the NuSTAR data was nearly identical and the cutoff powerlaw is not a statistically significant improvement. We suggest that the lack of Fe lines, and lack of cutoff in the powerlaw spectra (out to at least 60 keV), is atypical for an X-ray binary. \n\nWe performed a Lomb-Scargle analysis on the barycenter corrected X-ray data, and did not identify any periodic signals over the frequency range 1e-3 to 100 Hz, consistent with the EP/FXT report (GCN 40917). The periodogram becomes red noise dominated below 3e-3 Hz. \n\nFurther analysis is underway and additional NuSTAR and Swift observations are planned. \n\nWe thank the NuSTAR SOC, and in particular Karl Forster and Brian Grefenstette, for promptly implementing these observations.\n",
"published": "2025-07-07T17:46:53.773438Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-07T17:46:53.773454Z",
"modified": "2025-07-07T17:46:53.781911Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421116,
"topic": "gcn.circulars",
"uuid": "1383f8b6-05d0-48da-8f65-e1aa62afb3b8",
"title": "EP250702a/ GRB 250702B: NuSTAR X-ray Observations",
"submitter": "Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>",
"authors": "Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41014"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.41014....1O",
"eventId": "EP250702a",
"subject": "EP250702a/ GRB 250702B: NuSTAR X-ray Observations",
"createdOn": 1751910406231,
"submitter": "Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>",
"circularId": 41014,
"submittedHow": "web"
},
"message_text": "Brendan O’Connor (CMU), Dheeraj Pasham (Eureka Scientific/George Washington), Igor Andreoni (UNC), Jeremy Hare (Catholic/GSFC) report on behalf of a larger collaboration:\n\nWe observed the X-ray transient EP250702a (GCN 40906), which is also associated with the multiple gamma-ray triggers designated as GRB 250702B/D/E (GCNs 40883, 40886, 40890, 40891, 40931, 40903, 40914, 40923), with the NuSTAR X-ray Telescope through a Target of Opportunity observation through GO program 11282 (PI: Pasham). The observation occurred between 2025-07-03 20:45:21 and 2025-07-04 09:15:00 UTC for an on-source exposure of ~21.5 ks, simultaneous with Swift/XRT observations (ObsID: 19906002). \n\nThe source is clearly detected at an average rate of ~0.4 cts/s. The 3-79 keV X-ray lightcurve shows short term variability throughout the full exposure in both FPMA and FPMB, but no flaring is observed. The source varies in count rate by a factor of 2-3 on timescales as short as a few ks. Compared to NuSTAR observations of GRB 221009A at a similar count rate (GCNs 32695, 32788), the source shows more significant variability, which we suggest disfavors an ultralong GRB origin, especially in conjunction with the July 1st onset reported by the Einstein Probe (GCN 40906). \n\nThe X-ray spectra are featureless and do not show any Fe lines or reflection features. This is consistent with the lack of features in the Swift/XRT spectra. The 3-79 keV spectrum (FPMA+FPMB) is well fit by an absorbed powerlaw with a photon index of Gamma~1.81+/-0.03, which is consistent with the initial Swift/XRT spectral index within errors (GCN 40919). The hydrogen column density was fixed to 1e22 cm^-2 as per the best-fit Swift/XRT spectra (see https://www.swift.ac.uk/LSXPS/transients/9377) The unabsorbed 3-79 keV flux (time-averaged) is (2.35+/-0.05)e-11 erg/cm^2/s during our observation. \n\nWe also performed a fit with an absorbed cutoff powerlaw and find a cutoff energy >60 keV. In this case, the best-fit photon index is Gamma~1.67+/-0.08. This has better agreement with the EP/FXT result, although the FXT observation was obtained at an earlier time (GCN 40917). The C-stat between both fits to the NuSTAR data was nearly identical and the cutoff powerlaw is not a statistically significant improvement. We suggest that the lack of Fe lines, and lack of cutoff in the powerlaw spectra (out to at least 60 keV), is atypical for an X-ray binary. \n\nWe performed a Lomb-Scargle analysis on the barycenter corrected X-ray data, and did not identify any periodic signals over the frequency range 1e-3 to 100 Hz, consistent with the EP/FXT report (GCN 40917). The periodogram becomes red noise dominated below 3e-3 Hz. \n\nFurther analysis is underway and additional NuSTAR and Swift observations are planned. \n\nWe thank the NuSTAR SOC, and in particular Karl Forster and Brian Grefenstette, for promptly implementing these observations.\n",
"published": "2025-07-14T08:08:15.596627Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:15.596640Z",
"modified": "2025-07-14T08:08:15.599890Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 357011,
"topic": "gcn.circulars",
"uuid": "d3e5c32e-1769-46ce-841a-ff775f8f6bda",
"title": "EP250702a: WFST optical observations",
"submitter": "ylhua@pmo.ac.cn",
"authors": "ylhua@pmo.ac.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40943"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250702a",
"subject": "EP250702a: WFST optical observations",
"createdOn": 1751625746038,
"submitter": "ylhua@pmo.ac.cn",
"circularId": 40943,
"submittedHow": "web"
},
"message_text": "Yan-Long Hua, Jin-Jun Geng, Xue-Feng Wu, Hui Sun, Ye Li, Zhi-Ping Jin, Tian-Rui Sun, Yi-Fang Liang, Ding-Fang Hu, Yuan-Tai Yang, Ji-An Jiang report on behalf of the WFST team:\n\nFollowing the detection of EP250702a by Einstein Probe (Cheng et al., GCN 40906, 40917), Fermi/GBM (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890), Swift/BAT (via the GUANO system; DeLaunay et al., GCN 40903), and Konus/Wind (Frederiks et al., GCN 40914), all likely originating from the same astrophysical source (Neights et al., GCN 40891), the VLT (A. Martin-Carrillo et al., GCN 40924) identified a bright source that is absent in archival H- and K-band images from VISTA/VHS and UKIDSS.\n\nWe performed follow-up observations using the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at the Lenghu Astronomical Observation Base in Qinghai Province, China. Observations in the r-band began at 2025-07-03T17:26:10 UTC, approximately 28.29 hours after the trigger. The limiting magnitude of the stacked image reaches 22.19 (AB), and no unknown transient sources were detected in the region corresponding to the VLT observation.\n\nWe thank the WFST staff for supporting these observations.",
"published": "2025-07-04T10:42:35.072194Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-04T10:42:35.072210Z",
"modified": "2025-07-04T10:42:35.077931Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421211,
"topic": "gcn.circulars",
"uuid": "33cb31fa-b300-466a-b4fe-380eae610c55",
"title": "EP250702a: WFST optical observations",
"submitter": "ylhua@pmo.ac.cn",
"authors": "ylhua@pmo.ac.cn",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40943"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40943....1H",
"eventId": "EP250702a",
"subject": "EP250702a: WFST optical observations",
"createdOn": 1751625746038,
"submitter": "ylhua@pmo.ac.cn",
"circularId": 40943,
"submittedHow": "web"
},
"message_text": "Yan-Long Hua, Jin-Jun Geng, Xue-Feng Wu, Hui Sun, Ye Li, Zhi-Ping Jin, Tian-Rui Sun, Yi-Fang Liang, Ding-Fang Hu, Yuan-Tai Yang, Ji-An Jiang report on behalf of the WFST team:\n\nFollowing the detection of EP250702a by Einstein Probe (Cheng et al., GCN 40906, 40917), Fermi/GBM (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890), Swift/BAT (via the GUANO system; DeLaunay et al., GCN 40903), and Konus/Wind (Frederiks et al., GCN 40914), all likely originating from the same astrophysical source (Neights et al., GCN 40891), the VLT (A. Martin-Carrillo et al., GCN 40924) identified a bright source that is absent in archival H- and K-band images from VISTA/VHS and UKIDSS.\n\nWe performed follow-up observations using the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at the Lenghu Astronomical Observation Base in Qinghai Province, China. Observations in the r-band began at 2025-07-03T17:26:10 UTC, approximately 28.29 hours after the trigger. The limiting magnitude of the stacked image reaches 22.19 (AB), and no unknown transient sources were detected in the region corresponding to the VLT observation.\n\nWe thank the WFST staff for supporting these observations.",
"published": "2025-07-14T08:08:40.806803Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:40.806816Z",
"modified": "2025-07-14T08:08:40.809898Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421110,
"topic": "gcn.circulars",
"uuid": "0cf4e48a-8472-4d1b-9cfe-256191c29988",
"title": "EP 250704a: BOOTES-5 optical detection",
"submitter": "I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>",
"authors": "I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40957"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40957....1P",
"eventId": "EP250704a",
"subject": "EP 250704a: BOOTES-5 optical detection",
"createdOn": 1751652016811,
"submitter": "I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>",
"circularId": 40957,
"submittedHow": "web"
},
"message_text": "I. Perez-Garcia (IAA-CSIC, Granada), Y.-D. Hu (GXU), E. J. Fernandez-Garcia, M. D. Caballero-Garcia, S.-Y. Wu, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), I. M. Carrasco (SMA), M. Gritsevich (Univ. of Helsinki), C. Perez del Pulgar (Univ. of Malaga), S. Jeong (ADD, Daejeon), G. Garcia-Segura and D. Hiriart (IA-UNAM, Ensenada), D. R. Xiong (Yunnan Observatories of CAS, Kunming), and W. H. Lee (UNAM, Mexico DF), on behalf of a larger collaboration, report:\n\nFollowing the detection of EP 250704a by the Einstein Probe (Li et al., GCN 40941), the 0.6m BOOTES-5/JGU robotic telescope at San Pedro Martir Observatory (Mexico) automatically responded to this high-energy event starting on July 4, 08:33:01 UT (i.e., 16 min after detection). Series of images in clear filter were gathered and we detect an optical source consistent with the one reported by Becerra et al. and Bjørn et al. (GCN 40942, 40945). Using GaiaDR3 Gmag as a reference, we measure an initial magnitude of 20.1 +/- 0.2. Further analysis of the additional images is ongoing.\n\nWe would like to thank the staff at San Pedro Martir Observatory for their excellent support.",
"published": "2025-07-14T08:08:14.543042Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:14.543054Z",
"modified": "2025-07-14T08:08:14.546515Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 358989,
"topic": "gcn.circulars",
"uuid": "34be3bf3-d63d-4004-bb93-894821d64992",
"title": "EP 250704a: BOOTES-5 optical detection",
"submitter": "I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>",
"authors": "I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40957"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250704a",
"subject": "EP 250704a: BOOTES-5 optical detection",
"createdOn": 1751652016811,
"submitter": "I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>",
"circularId": 40957,
"submittedHow": "web"
},
"message_text": "I. Perez-Garcia (IAA-CSIC, Granada), Y.-D. Hu (GXU), E. J. Fernandez-Garcia, M. D. Caballero-Garcia, S.-Y. Wu, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), I. M. Carrasco (SMA), M. Gritsevich (Univ. of Helsinki), C. Perez del Pulgar (Univ. of Malaga), S. Jeong (ADD, Daejeon), G. Garcia-Segura and D. Hiriart (IA-UNAM, Ensenada), D. R. Xiong (Yunnan Observatories of CAS, Kunming), and W. H. Lee (UNAM, Mexico DF), on behalf of a larger collaboration, report:\n\nFollowing the detection of EP 250704a by the Einstein Probe (Li et al., GCN 40941), the 0.6m BOOTES-5/JGU robotic telescope at San Pedro Martir Observatory (Mexico) automatically responded to this high-energy event starting on July 4, 08:33:01 UT (i.e., 16 min after detection). Series of images in clear filter were gathered and we detect an optical source consistent with the one reported by Becerra et al. and Bjørn et al. (GCN 40942, 40945). Using GaiaDR3 Gmag as a reference, we measure an initial magnitude of 20.1 +/- 0.2. Further analysis of the additional images is ongoing.\n\nWe would like to thank the staff at San Pedro Martir Observatory for their excellent support.",
"published": "2025-07-04T18:00:26.197523Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-04T18:00:26.197542Z",
"modified": "2025-07-04T18:00:26.201097Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 356809,
"topic": "gcn.circulars",
"uuid": "df9759be-693b-4242-9f58-0be0aaa7bb2c",
"title": "EP250704a: COLIBRÍ optical counterpart candidate",
"submitter": "Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>",
"authors": "Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40942"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250704a",
"subject": "EP250704a: COLIBRÍ optical counterpart candidate",
"createdOn": 1751623099102,
"submitter": "Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>",
"circularId": 40942,
"submittedHow": "web"
},
"message_text": "Benjamin Schneider (LAM), Rosa L. Becerra (U Roma), Sarah Antier (OCA), William H. Lee (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Fredd Alvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field the EP250704a (Li et al., GCN 40941) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-07-04 08:27 to 08:46 UTC (from 10.8 to 30.0 minutes after the trigger and starting 25 seconds after the arrival of the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn our stacked image, we detect a new source not visible in the PanSTARRS catalogue at:\n\nRA(J2000) = 20:03:29.51 = 300.8729 degrees\nDec(J2000) = +12:01:23.46 = 12.0232 degrees\n\nwith an uncertainty of 0.5 arcsec and within the EP/FXT region (Li et al., GCN 40941). We measure a preliminary magnitude of:\n\ni = 20.46 +/- 0.06\n\nWe suggest this is the optical counterpart of EP250704a.\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.\n",
"published": "2025-07-04T09:58:26.261432Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-04T09:58:26.261448Z",
"modified": "2025-07-04T09:58:26.270310Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421212,
"topic": "gcn.circulars",
"uuid": "9a7795be-830a-445e-930f-b44034a6ea9e",
"title": "EP250704a: COLIBRÍ optical counterpart candidate",
"submitter": "Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>",
"authors": "Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40942"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40942....1S",
"eventId": "EP250704a",
"subject": "EP250704a: COLIBRÍ optical counterpart candidate",
"createdOn": 1751623099102,
"submitter": "Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>",
"circularId": 40942,
"submittedHow": "web"
},
"message_text": "Benjamin Schneider (LAM), Rosa L. Becerra (U Roma), Sarah Antier (OCA), William H. Lee (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Fredd Alvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM):\n\nWe imaged the field the EP250704a (Li et al., GCN 40941) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-07-04 08:27 to 08:46 UTC (from 10.8 to 30.0 minutes after the trigger and starting 25 seconds after the arrival of the notice) and obtained 16 minutes of exposure in the i filter.\n\nThe data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nIn our stacked image, we detect a new source not visible in the PanSTARRS catalogue at:\n\nRA(J2000) = 20:03:29.51 = 300.8729 degrees\nDec(J2000) = +12:01:23.46 = 12.0232 degrees\n\nwith an uncertainty of 0.5 arcsec and within the EP/FXT region (Li et al., GCN 40941). We measure a preliminary magnitude of:\n\ni = 20.46 +/- 0.06\n\nWe suggest this is the optical counterpart of EP250704a.\n\nFurther observations and analysis are ongoing.\n\nWe thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.\n\nCOLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.\n",
"published": "2025-07-14T08:08:40.815233Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:40.815246Z",
"modified": "2025-07-14T08:08:40.818437Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 421170,
"topic": "gcn.circulars",
"uuid": "9eada04d-21e7-4578-819b-00752e3db891",
"title": "EP250704a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40941"
},
"format": "text/markdown",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40941....1L",
"eventId": "EP250704a",
"subject": "EP250704a: Einstein Probe detection of an X-ray transient",
"createdOn": 1751622647923,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40941,
"submittedHow": "web"
},
"message_text": "A. Li (BNU), Y.H Cheng (SWIFAR,YNU), C. Zhou (HUST), G.Y. Zhao (SYSU), Y. J. Zhang (THU) and W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250704a. The transient triggered EP-WXT (ID: 01709181144) at 2025-07-04T08:16:52 (UTC). The WXT position of the source is R.A. = 300.872 deg, DEC = 12.030 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 300.8742, DEC = 12.0243 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nThis transient is temporally coincidence with GRB 250704B (GCN 40940). Further information will be updated when the telemetry data is received. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-07-14T08:08:38.387508Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:38.387521Z",
"modified": "2025-07-14T08:08:38.390710Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 356776,
"topic": "gcn.circulars",
"uuid": "851c273f-3102-4726-8d02-719f965d4fb2",
"title": "EP250704a: Einstein Probe detection of an X-ray transient",
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40941"
},
"format": "text/markdown",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250704a",
"subject": "EP250704a: Einstein Probe detection of an X-ray transient",
"createdOn": 1751622647923,
"submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"circularId": 40941,
"submittedHow": "web"
},
"message_text": "A. Li (BNU), Y.H Cheng (SWIFAR,YNU), C. Zhou (HUST), G.Y. Zhao (SYSU), Y. J. Zhang (THU) and W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250704a. The transient triggered EP-WXT (ID: 01709181144) at 2025-07-04T08:16:52 (UTC). The WXT position of the source is R.A. = 300.872 deg, DEC = 12.030 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).\n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 300.8742, DEC = 12.0243 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).\n\nThis transient is temporally coincidence with GRB 250704B (GCN 40940). Further information will be updated when the telemetry data is received. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
"published": "2025-07-04T09:50:56.852441Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-04T09:50:56.852458Z",
"modified": "2025-07-04T09:50:56.857713Z",
"nonlocalizedevents": [],
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},
{
"id": 421299,
"topic": "gcn.circulars",
"uuid": "aeb55183-053e-4034-9a9a-98e805bbb1ed",
"title": "EP250704a/GRB 250704B: 10 GHz VLA detection",
"submitter": "Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>",
"authors": "Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41046"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.41046....1R",
"eventId": "EP250704a",
"subject": "EP250704a/GRB 250704B: 10 GHz VLA detection",
"createdOn": 1752037027820,
"submitter": "Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>",
"circularId": 41046,
"submittedHow": "web"
},
"message_text": "Roberto Ricci, Rosa L. Becerra, Eleonora Troja (Rome U.) report on behalf of the ERC BHianca team:\n\nWe observed the field of GRB 250704B/EP250704a (Wang et al. GCN 40940; Li et al. GCN 40491) with the Jansky Very Large Array (VLA) at the center frequency of 10 GHz (with a bandwidth of 4 GHz) in C-array configuration on 2025 July 8th at mid observing time 07:53 UT (3.98 days after burst). \n\nA radio source was detected within the error circle of optical transient position (Schneider et al. GCN 40942) with a flux density of 92 +/- 7 microJy.\n\nThis is consistent with the radio detection reported by Schroeder et al. GCN 41038.\n\nFurther observations are planned. \n\nWe thank the VLA staff for executing the observations. \n",
"published": "2025-07-14T08:08:46.718598Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-14T08:08:46.718610Z",
"modified": "2025-07-14T08:08:46.722270Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 387639,
"topic": "gcn.circulars",
"uuid": "c8fbeb0f-7670-4ee7-bda0-3f33db22186e",
"title": "EP250704a/GRB 250704B: 10 GHz VLA detection",
"submitter": "Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>",
"authors": "Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/41046"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.4.0/gcn/circulars.schema.json",
"eventId": "EP250704a",
"subject": "EP250704a/GRB 250704B: 10 GHz VLA detection",
"createdOn": 1752037027820,
"submitter": "Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>",
"circularId": 41046,
"submittedHow": "web"
},
"message_text": "Roberto Ricci, Rosa L. Becerra, Eleonora Troja (Rome U.) report on behalf of the ERC BHianca team:\n\nWe observed the field of GRB 250704B/EP250704a (Wang et al. GCN 40940; Li et al. GCN 40491) with the Jansky Very Large Array (VLA) at the center frequency of 10 GHz (with a bandwidth of 4 GHz) in C-array configuration on 2025 July 8th at mid observing time 07:53 UT (3.98 days after burst). \n\nA radio source was detected within the error circle of optical transient position (Schneider et al. GCN 40942) with a flux density of 92 +/- 7 microJy.\n\nThis is consistent with the radio detection reported by Schroeder et al. GCN 41038.\n\nFurther observations are planned. \n\nWe thank the VLA staff for executing the observations. \n",
"published": "2025-07-09T04:57:17.030816Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-07-09T04:57:17.030834Z",
"modified": "2025-07-09T04:57:17.035708Z",
"nonlocalizedevents": [],
"targets": []
}
]
}