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"results": [
{
"id": 186425,
"topic": "gcn.circulars",
"uuid": "c329a163-b978-434f-91d5-65c0d1325f11",
"title": "EP20250416a: Swift/XRT counterpart detection",
"submitter": "Tullia Sbarrato at INAF-OAB <tullia.sbarrato@inaf.it>",
"authors": "Tullia Sbarrato at INAF-OAB <tullia.sbarrato@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40163"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.2.0/gcn/circulars.schema.json",
"bibcode": "2025GCN.40163....1S",
"subject": "EP20250416a: Swift/XRT counterpart detection",
"createdOn": 1744902418196,
"submitter": "Tullia Sbarrato at INAF-OAB <tullia.sbarrato@inaf.it>",
"circularId": 40163,
"submittedHow": "web"
},
"message_text": "T. Sbarrato (INAF-OAB), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), C. Salvaggio (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of EP/WXT-detected transient EP 250416a (Zhao et al., GCN 40154). We searched for X-ray sources in 2.0 ks of Photon Counting (PC) mode data, from T0+17.1 ks to T0+23.2 ks after the EP/WXT trigger. \nAn uncatalogued X-ray source is detected within the estimated 3-sigma EP/WXT error region. \nUsing 2000 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 256.41935, +25.7751 which is equivalent to:\n\nRA (J2000): 17h 05m 40.64s\nDec(J2000): +25d 46’ 30.4\"\n\nwith an uncertainty of 3.1 arcsec (radius, 90% confidence). This position is 1 arcmin from the EP/WXT position, and consistent with the optical candidate reported by Levan et al., (GCN 40160).\n\nThe source has a mean count rate of 9.9e-02 ct/sec and currently shows no signs of fading.\n\nThe results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/EP/EP_FIELD00034/\n\nThis circular is an official product of the Swift-XRT team.\n\n",
"published": "2025-05-10T16:09:50.983194Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-05-10T16:09:50.983212Z",
"modified": "2025-05-10T16:09:50.986316Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 186201,
"topic": "gcn.circulars",
"uuid": "111c19c8-c46d-4ad1-9667-85ea5c6c9369",
"title": "EP20250416a: Swift/XRT counterpart detection",
"submitter": "Tullia Sbarrato at INAF-OAB <tullia.sbarrato@inaf.it>",
"authors": "Tullia Sbarrato at INAF-OAB <tullia.sbarrato@inaf.it>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/40163"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.2.0/gcn/circulars.schema.json",
"subject": "EP20250416a: Swift/XRT counterpart detection",
"createdOn": 1744902418196,
"submitter": "Tullia Sbarrato at INAF-OAB <tullia.sbarrato@inaf.it>",
"circularId": 40163,
"submittedHow": "web"
},
"message_text": "T. Sbarrato (INAF-OAB), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), C. Salvaggio (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of EP/WXT-detected transient EP 250416a (Zhao et al., GCN 40154). We searched for X-ray sources in 2.0 ks of Photon Counting (PC) mode data, from T0+17.1 ks to T0+23.2 ks after the EP/WXT trigger. \nAn uncatalogued X-ray source is detected within the estimated 3-sigma EP/WXT error region. \nUsing 2000 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 256.41935, +25.7751 which is equivalent to:\n\nRA (J2000): 17h 05m 40.64s\nDec(J2000): +25d 46’ 30.4\"\n\nwith an uncertainty of 3.1 arcsec (radius, 90% confidence). This position is 1 arcmin from the EP/WXT position, and consistent with the optical candidate reported by Levan et al., (GCN 40160).\n\nThe source has a mean count rate of 9.9e-02 ct/sec and currently shows no signs of fading.\n\nThe results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/EP/EP_FIELD00034/\n\nThis circular is an official product of the Swift-XRT team.\n\n",
"published": "2025-05-10T16:09:48.726344Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-05-10T16:09:48.726362Z",
"modified": "2025-05-10T16:09:48.729519Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6315,
"topic": "gcn.circular",
"uuid": "559c0459-72b1-4759-a4bc-d53d1a6ef46d",
"title": "EP240331A: MASTER optical observations",
"submitter": "Hop gcn.circular",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"date": "24/04/01 22:05:20 GMT",
"from": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36009"
},
"title": "GCN CIRCULAR",
"number": "36009",
"subject": "EP240331A: MASTER optical observations"
},
"message_text": "\nV.Lipunov, P.Balanutsa (Lomonosov MSU), D.Buckley (SAAO), O.Gress, N.Budnev (ISU),E.Gorbovskoy, Ya.Kechin,\nK.Zhirkov, A.Kuznetsov, D.Vlasenko, Yu.Tselik,N.Tiurina, I.Gorbunov, V.Vladimirov,D.Zimnukhov, V.Senik,\nA.Yudin,A.Chasovnikov, D.Cheryasov(Lomonosov MSU,SAI,PhysicsDepartment),\nA.Sosnovskij (Crimean Astrophysical Observatory, RAS),\nC.Francile. F. Podesta, R.Podesta (Observatorio Astronomico Felix Aguilar OAFA),\nR. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)\n\nMASTER Global robotic net (http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)\nstarted EP240331A ( Pan et al. ATel #16564, Center:169.414 -20.042 +-20';trigger 2024-03-31 22:07:17UT; Notice=1 Apr 2024 16:14 UT)\nat 2024-04-01 20:43:31 after MeerLICHT GCN 36007 (Groot et al.)\n\nMASTER-SAAO robotic telescope located in South African Astronomical Observatory was pointed to the EP-WXT Alert 240331.92 (11h 17m 39.36s , -20d 02m 31.2s, R=0.2) errorbox 81374 sec after trigger time at 2024-04-01 20:43:31 UT,\nwith upper limit up to 19.0 mag. The observations began at zenith distance = 14 deg. The sun altitude is -51.1 deg.\n\nMASTER-Tavrida robotic telescope was pointed at 2024-04-01 20:47:05 UT, with upper limit up to 16.1 mag.\nThe observations began at zenith distance = 64 deg. The sun altitude is -39.4 deg.\n\nMASTER-Kislovodsk robotic telescope was pointed at 2024-04-01 21:22:51 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 67 deg. The sun altitude is -42.1 deg.\n\nThe galactic latitude b = 38 deg., longitude l = 276 deg.\n\nReal time updated cover map and OT discovered available here:\nhttps://master.sai.msu.ru/site/master2/observ.php?id$12001\n\nWe obtain the following upper limits.\n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n\n 81405 | 2024-04-01 20:43:31 | MASTER-SAAO | (11h 14m 32.28s , -19d 56m 04.1s) | C | 60 | 18.9 |\n 81405 | 2024-04-01 20:43:31 | MASTER-SAAO | (11h 16m 31.77s , -20d 09m 11.5s) | C | 60 | 18.9 |\n 81485 | 2024-04-01 20:44:51 | MASTER-SAAO | (11h 14m 29.81s , -19d 54m 44.8s) | C | 60 | 18.8 |\n 81485 | 2024-04-01 20:44:51 | MASTER-SAAO | (11h 16m 29.29s , -20d 07m 52.1s) | C | 60 | 18.9 |\n 81564 | 2024-04-01 20:46:11 | MASTER-SAAO | (11h 14m 30.49s , -19d 55m 52.3s) | C | 60 | 18.8 |\n 81564 | 2024-04-01 20:46:11 | MASTER-SAAO | (11h 16m 30.01s , -20d 08m 59.1s) | C | 60 | 18.9 |\n 81724 | 2024-04-01 20:48:50 | MASTER-SAAO | (11h 14m 29.27s , -19d 55m 18.4s) | C | 60 | 18.8 |\n 81724 | 2024-04-01 20:48:50 | MASTER-SAAO | (11h 16m 28.80s , -20d 08m 25.5s) | C | 60 | 18.9 |\n 81864 | 2024-04-01 20:50:10 | MASTER-SAAO | (11h 14m 29.42s , -19d 54m 16.8s) | C | 180 | 18.9 |\n 81864 | 2024-04-01 20:50:10 | MASTER-SAAO | (11h 16m 28.95s , -20d 07m 23.8s) | C | 180 | 18.8 |\n 82064 | 2024-04-01 20:53:30 | MASTER-SAAO | (11h 14m 37.88s , -19d 55m 13.6s) | C | 180 | 18.9 |\n\nObservations and reduction will be continued\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36009.",
"published": "2024-04-01T22:05:37.527807Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-01T22:05:37.527821Z",
"modified": "2024-04-01T22:05:37.534379Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6438,
"topic": "gcn.circular",
"uuid": "4c3cd975-b0e8-4e00-bf7e-1df658a5dbaa",
"title": "EP240408a: BOOTES-6/DPRT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"data": {
"date": "24/04/09 23:00:10 GMT",
"from": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36056"
},
"title": "GCN CIRCULAR",
"number": "36056",
"subject": "EP240408a: BOOTES-6/DPRT optical upper limit"
},
"message_text": "I. Perez-Garcia, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, S.-Y. Wu and A. J. Castro-Tirado (IAA-CSIC, Granada), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland), M. Gritsevich (Univ. of Helsinki) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report:\n\nFollowing the detection of the fast X-ray transient EP240408a by the Einstein Probe (Hu et al. GCNC 36053), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) observed the fast X-ray transient location starting on Apr 9, 18:54 UT (~ 25 h after trigger) in different optical bands. No new optical source is detected on the co-added images (clear-filter) within the EP/WXT error box down to 20.5 mag.\n\nWe thank the staff at Boyden Observatory for their excellent support.\n\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36056.",
"published": "2024-04-09T23:00:25.404276Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-09T23:00:25.404292Z",
"modified": "2024-04-09T23:00:25.413226Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6435,
"topic": "gcn.circular",
"uuid": "2b0b35f2-31c7-460a-9868-d00266f7ff7d",
"title": "EP240408a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/09 10:31:03 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36053"
},
"title": "GCN CIRCULAR",
"number": "36053",
"subject": "EP240408a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "J. W. Hu, D. H. Zhao, Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, T. Y. Lian, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA), on behalf of the Einstein Probe team \n \nWe report on the detection of a fast X-ray transient EP240408a at 2024-04-08T17:56:30 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The position of the source is R.A. = 158.840 deg, DEC = -35.749 deg (J2000) with an uncertainty of 3 arcmin (radius, 90% C.L. statistical and systematic). The light curve of the source shows a duration of approximately 10 seconds. The peak flux reaches ~1.4 x 10^-8 erg/s/cm^2 in the 0.5-4.0 keV band. The averaged spectrum can be fitted by an absorbed power-law with NH fixed at the Galactic value of 6.23 x 10^20 cm^-2 and a photon index of 1.1(-0.7/+0.8). The derived average unabsorbed 0.5-4.0 keV flux is 4.0(-1.3/+1.3) x 10^-9 erg/s/cm^2. \n\nNo previously known bright X-ray sources have been found within the 3 arcmin region around the source position. The derived source parameters may be subject to larger uncertainties than those quoted here since in-orbit calibration of the instrument is still in progress. \n\nFurther follow-up observations are strongly encouraged to identify the nature of this X-ray transient.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36053.",
"published": "2024-04-09T10:31:22.815123Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-09T10:31:22.815136Z",
"modified": "2024-04-09T10:31:22.825284Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6525,
"topic": "gcn.circular",
"uuid": "55f3a3b2-ee1c-4155-b2fa-c6aa78249826",
"title": "EP240408a: GSP optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/04/13 09:09:26 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36079"
},
"title": "GCN CIRCULAR",
"number": "36079",
"subject": "EP240408a: GSP optical upper limit"
},
"message_text": "W. X. Li, S. J. Xue, D. Xu (NAOC), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report:\nFollowing the detection of the fast X-ray transient EP240408a by the Einstein Probe (Hu et al. GCN 36053), we initiated observations of the fast X-ray transient location starting on April 9 at 10:46 UT (~17 hours after the trigger) in the r band. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at Siding Spring Observatory in Australia.\nWe report that no new optical source was detected in the co-added images within the EP/WXT error box down to ~21.5 mag.\nThese observations were taken as part of the Global Supernova Project.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36079.",
"published": "2024-04-13T09:09:45.207214Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-13T09:09:45.207236Z",
"modified": "2024-04-13T09:09:45.248692Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6449,
"topic": "gcn.circular",
"uuid": "c5e8d1a2-3374-4dd9-8f71-17ceb0ff71b9",
"title": "EP240408A: MASTER optical observations",
"submitter": "Hop gcn.circular",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"date": "24/04/10 11:59:24 GMT",
"from": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36060"
},
"title": "GCN CIRCULAR",
"number": "36060",
"subject": "EP240408A: MASTER optical observations"
},
"message_text": "G.Antipov, V.Lipunov, P.Balanutsa (Lomonosov MSU), D.Buckley (SAAO), K.Zhirkov, A.Kuznetsov,\nN.Tiurina, E.Gorbovskoy, Ya.Kechin, D.Vlasenko, Yu.Tselik,I.Gorbunov,\nV.Vladimirov,D.Zimnukhov, V.Senik, A.Yudin,A.Chasovnikov, D.Cheryasov(Lomonosov MSU,SAI,PhysicsDepartment),\nO.Gress,N.Budnev(ISU),\nA.Sosnovskij (Crimean Astrophysical Observatory, RAS),\nC.Francile. F. Podesta, R.Podesta (Observatorio Astronomico Felix AguilarOAFA),\nR. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)\n\nMASTER Global robotic net (http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)\nstarted EP 240408A (Hu et al. #GCN 36053, Triggertime= 2024-04-08 17:56:30UT,\nNotice 24-04-09T10:31:03, Center R.A.,Dec. = 158.851 -35.747)\noptical (unfiltered) observation by MASTER-SAAO robotic telescope, located in South Africa, at 2024-04-09 17:08:35UT .\n\nThere is no optical transient with mlim\u0019.5(unfiltered) at Swift XRT ( #GCN 36057\n158.851 deg, DEC = -35.747 (10:35:24.24 -35:44:49.20) )\nand at GROND positions (Rau et al. GCN 36059 10:35:22.44 -35:44:08.2)\n~23h after trigger time\n\nObservation started at 55deg altitude. Sun altitude was 11 deg.\nReduction will be continued.\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36060.",
"published": "2024-04-10T11:59:41.773292Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-10T11:59:41.773305Z",
"modified": "2024-04-10T11:59:41.779135Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6443,
"topic": "gcn.circular",
"uuid": "c581650a-629c-4c22-9aa2-2354a1c8ea3e",
"title": "EP240408a: Swift follow-up observation",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/10 08:13:41 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36057"
},
"title": "GCN CIRCULAR",
"number": "36057",
"subject": "EP240408a: Swift follow-up observation"
},
"message_text": "J. W. Hu, D. H. Zhao, Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, T. Y. Lian, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA), on behalf of the Einstein Probe team \n\nFollowing up on the new X-ray flare EP240408a detected by Einstein Probe (Hu et al., GCN 36053), we performed a target of opportunity observation with Swift. The Swift XRT observation began at 2024-04-10T02:57:40 (UTC) with an exposure time of 966 seconds in the Photon Counting mode, about 33 hours after the burst detected by EP-WXT. An X-ray source was detected at R.A. = 158.851 deg, DEC = -35.747 deg, with an uncertainty of 3.68 arcsec (radius, 90% C.L. statistical and systematic), 32 arcsec away from the position of EP240408a. The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 6.23 x 10^20 cm^-2 and a photon index of 1.9(-0.2, +0.2). The derived average unabsorbed 0.5-4.0 keV flux is 1.2(-0.1,+0.3) x 10^-11 erg/s/cm2 (90% C.L.). There is no catalogued X-ray source within the error circle, suggesting that this XRT source is most likely associated with EP240408a. No significant counterpart was detected in the UVOT image within the error circle of the XRT position. \n\nFurther follow-up observations are encouraged to identify the nature of this X-ray transient. \n\nWe thank the Neil Gehrels Swift Observatory team for making the ToO observation possible. \n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36057.",
"published": "2024-04-10T08:13:55.016181Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-10T08:13:55.016207Z",
"modified": "2024-04-10T08:13:55.024814Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6444,
"topic": "gcn.circular",
"uuid": "ecd44803-625b-48a3-8395-acb8897089f2",
"title": "EP240408a: Upper limits from GECAM-B Observation",
"submitter": "Hop gcn.circular",
"authors": "Chenwei Wang at IHEP <cwwang@ihep.ac.cn>",
"data": {
"date": "24/04/10 08:24:06 GMT",
"from": "Chenwei Wang at IHEP <cwwang@ihep.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36058"
},
"title": "GCN CIRCULAR",
"number": "36058",
"subject": "EP240408a: Upper limits from GECAM-B Observation"
},
"message_text": "Chen-Wei Wang, Shao-Lin Xiong, Jia-Cong Liu, Cheng-Kui Li and Chao Zheng, report on behalf of the GECAM team:\n\nGECAM-B was observing normally and covered the sky region of EP240408a at event time 2024-04-08T17:56:30 (UTC). The smallest incident angle of GECAM-B GRD detectors is about 27.3 deg for the WXT location (RA\u00158.840 deg, Dec=-35.749 deg).\n\nThere was no GECAM-B in-flight trigger around the event time of EP240408a. An automated, blind search for gamma-ray bursts of GECAM-B data found no burst candidates. The targeted search was run within +/-150 s around event time, and also identified no counterpart candidates.\n\nWith the three typical GRB spectral models, integration time of 10 s (which is the duration of the EP240408a) and the WXT localization, the 3-sigma upper-limits of fluence (15 - 300 keV, incident energy) are reported below:\n\nBand model 1 (alpha=-1.9, beta=-3.7, Epp keV): 2.4e-6erg cm^-2\nBand model 2 (alpha=-1.0, beta=-2.3, Ep#0 keV): 3.5e-6 erg cm^-2\nBand model 3 (alpha=0.0, beta=-1.5, Ep\u001000 keV): 4.3e-6 erg cm^-2\n\nAll measurements above are made with the GRD detector which has the smallest incident angle to this source.\n\nWe note that these results are preliminary and refined analysis will be reported later.\n\nGravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36058.",
"published": "2024-04-10T08:24:20.133639Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-10T08:24:20.133652Z",
"modified": "2024-04-10T08:24:20.139879Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6445,
"topic": "gcn.circular",
"uuid": "d20fdf7b-b1bd-403c-9352-e3279bdce92f",
"title": "EP240410a: GROND detection of a candidate counterpart",
"submitter": "Hop gcn.circular",
"authors": "Arne Rau at MPE <arau@mpe.mpg.de>",
"data": {
"date": "24/04/10 09:18:25 GMT",
"from": "Arne Rau at MPE <arau@mpe.mpg.de>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36059"
},
"title": "GCN CIRCULAR",
"number": "36059",
"subject": "EP240410a: GROND detection of a candidate counterpart"
},
"message_text": "Arne Rau (MPE):\n\nWe observed the position of EP240408a (Hu et al., #GCN 36053; #36057) with the Gamma-ray Burst Optical Near-ir Detector (GROND, Greiner et al. 2008) starting on April 10, 2024, 04:14:09 UTC. A faint source is detected in the Swift/XRT error circle located at RA = 10:35:22.44, Dec = -35:44:08.2 with an uncertainty of 0.2â in both coordinates.\n\nThe source is detected in the J and H bands at the following AB magnitudes:\n\nJ= 19.9 +/- 0.3\nH= 20.5 +/- 0.5\n\nThe photometric uncertainties are dominated by a very bright point source ~20 arcsec from the optical/NIR counterpart.\n\nWe note that the source is also visible in the z-band data of the Legacy Survey DR10 (https://www.legacysurvey.org/).\n\nWe thank the 2.2m staff member, Angela Hempel, for the rapid execution of the observation.\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36059.",
"published": "2024-04-10T09:18:45.910909Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-10T09:18:45.910923Z",
"modified": "2024-04-10T09:18:45.916925Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6617,
"topic": "gcn.circular",
"uuid": "f939af14-4563-4f91-a35b-2155f0e61647",
"title": "EP240413a: BOOTES-2/TELMA Optical Upper Limit",
"submitter": "Hop gcn.circular",
"authors": "Dingrong Xiong at Yunnan Observatories of CAS, China <xiongdingrong@ynao.ac.cn>",
"data": {
"date": "24/04/16 13:10:33 GMT",
"from": "Dingrong Xiong at Yunnan Observatories of CAS, China <xiongdingrong@ynao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36135"
},
"title": "GCN CIRCULAR",
"number": "36135",
"subject": "EP240413a: BOOTES-2/TELMA Optical Upper Limit"
},
"message_text": "D. R. Xiong, J. M. Bai, J. R. Mao, Y. F. Fan, K. Ye, C. J. Wang, Y. X. Xin, B. L. Lun, J. J. Zhang, X. H. Zhao, L. Xu, K. X. Lu, X. Ding, D. Q. Wang, S. S. He(Yunnan Observatories/CAS), A. J. Castro-Tirado, E. Fernandez-Garcia, Y. D. Hu (IAA-CSIC) and C. J. Perez del Pulgar (UMA) on behalf of the BOOTES team report:\n\nWe observed the fast X-ray transient EP240413a (R.A. = 228.815 deg, DEC = -18.503 deg; Lian et al., GCN 36086, Li et al., GCN 36092) with BOOTES-2/TELMA robotic telescope, and did not found any optical counterpart within an uncertainty of 30 arcsec in radius.\n\nThe upper limits of magnitudes (without being corrected for Galactic extinction) are given as follows.\n\nFXT T0 | Tmid-T0 (day) | UT (start) | Upper Limit (error) | Exposure Time | Filter\n\n--------------------------------------------------------------------------------------------------------------\n\n24-04-14T04:40:26| 0.86 | 04-15T01:21:09 | 17.623 (0.13) | 10*60s (co-added) | Clear\n\n---------------------------------------------------------------------------------------------------------------\n\nThe Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998 (Castro-Tirado et al. 1999; Hu et al. 2021). The BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain). We acknowledge the support of these staffs from the BOOTES telescope networks.\n\n=================================================================\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36135.",
"published": "2024-04-16T13:10:50.016946Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-16T13:10:50.016962Z",
"modified": "2024-04-16T13:10:50.024678Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6548,
"topic": "gcn.circular",
"uuid": "c4a27117-721f-4411-9413-47a2f4f7e257",
"title": "EP240413a: EP-WXT detection of a fast X-ray transient ",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/14 05:05:38 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36086"
},
"title": "GCN CIRCULAR",
"number": "36086",
"subject": "EP240413a: EP-WXT detection of a fast X-ray transient "
},
"message_text": "T. Y. Lian, X. Pan, Z. X. Ling, Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Yang, C. Y. Dai (NJU), Z. T. Fang (PMO), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n \nWe report on the detection of a fast X-ray transient EP240413a at 2024-04-13T14:39:37 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The position of the source is R.A. = 228.794 deg, DEC = -18.800 deg (J2000) with an uncertainty of 20 arcmin in radius (90% C.L. statistical and systematic). The larger positioning uncertainty than the nominal value is due to the so far incomplete calibration of the WXT module which detected the source. The transient event lasts for ~200 seconds and has a peak flux of ~7 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.6(-0.2/+0.1) (with the column density fixed at the Galactic value of 1.12 x 10^21 cm^-2), giving an unabsorbed flux of 1.1(-0.1/+0.1) x 10^-9 erg/s/cm2 in the 0.5-4 keV band. The 1-sigma uncertainties are given for the above parameters. We note that the derived source parameters may be subject to larger uncertainties than those quoted here since in-orbit calibration of the instrument is still in progress.\n \nNo previously known X-ray sources at a similar flux level are found within the 20 arcmin region around the source position.\n \nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36086.",
"published": "2024-04-14T05:05:54.730383Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-14T05:05:54.730406Z",
"modified": "2024-04-14T05:05:54.736437Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6568,
"topic": "gcn.circular",
"uuid": "a8e0eae8-01c7-4f70-ba44-a4c1a368abe2",
"title": "EP240413A: GOTO optical upper limits",
"submitter": "Hop gcn.circular",
"authors": "kendall.ackley@warwick.ac.uk",
"data": {
"date": "24/04/14 20:04:34 GMT",
"from": "kendall.ackley@warwick.ac.uk",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36098"
},
"title": "GCN CIRCULAR",
"number": "36098",
"subject": "EP240413A: GOTO optical upper limits"
},
"message_text": "K. Ackley; B. P. Gompertz; P. O'Brien; G. Ramsay; A. Levan; R. Starling; M. J. Dyer; J. Lyman; K. Ulaczyk; F. Jimenez-Ibarra; A. Kumar; D. O'Neill; D. Steeghs; D. K. Galloway; V. Dhillon; K. Noysena; R. Kotak; R. P. Breton; L. K. Nuttall; E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration:\n\nThe Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022) performed a targeted observation in response to the EP-WXT trigger EP240413A (Lian et al., GCN 36086) at 11:42:34 UT on 2024-04-14, starting approximately 21 hours after the EP-WXT trigger and 7 hours after EP-FXT follow-up observations (Li et al., GCN 36092). The observation consisted of a 6x60s exposure in the GOTO L-band (400-700 nm).\n\nImages were processed immediately after acquisition using the GOTO pipeline. No optical counterpart to the X-ray counterpart candidate detected by EP-FXT (Li et al., GCN 36092) is seen to a 3-sigma limit of L > 20.4 magnitudes (AB). The last visit to this field occurred at 14:27:11 on 2024-04-13, approximately 12 minutes before the EP-WXT trigger, providing a pre-detection 3-sigma limit of L > 21.1 magnitudes (AB).\n\nMagnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.\n\nGOTO (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\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36098.",
"published": "2024-04-14T20:04:50.653793Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-14T20:04:50.653813Z",
"modified": "2024-04-14T20:04:50.665705Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6562,
"topic": "gcn.circular",
"uuid": "be7c23a7-dae0-454f-8302-0e57dbdef5a3",
"title": "EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/14 16:17:35 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36092"
},
"title": "GCN CIRCULAR",
"number": "36092",
"subject": "EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours"
},
"message_text": "C. K. Li, S.M. Jia, Y. Chen, W. W. Cui, H. Feng, J. Guan, D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA), T. Y. Lian, X. Pan, Z. X. Ling, Y. Liu, H. Sun, D. Y. Li, H. Y. Liu, W. Yuan, C. Zhang (NAOC, CAS) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240413a (Lian et al., GCN 36086) by the Wide-field X-ray Telescope (WXT) of Einstein Probe (EP), we performed an observation with the Follow-up X-ray Telescope (FXT) on board EP. The observation started at 2024-04-14T04:40:26, about 14 hours after the WXT detection, with a net exposure time of 9.3 ks.\n\nAn X-ray source was clearly detected at R.A. = 228.815 deg, DEC = -18.503 deg, with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic). There is no cataloged X-ray source within the error circle. Considering this source being within the error circle of the WXT source (17.9 arcmin away), we tend to suggest it to be possibly associated with EP240413a. If this is true, EP240413a has faded by about 3 orders of magnitude in X-ray flux in about 14 hours. The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 1.1e21 cm-2 and a photon index of 2.2(+/-0.3) (90% C.L.). The derived unabsorbed flux in 0.5-10 keV is 5.3(+/-0.5)e-13 erg/s/cm2 (90% C.L.). Further monitoring of EP240413a with FXT is planned for the next few days.\n\nPlease note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36092.",
"published": "2024-04-14T16:17:50.428182Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-14T16:17:50.428198Z",
"modified": "2024-04-14T16:17:50.436062Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6576,
"topic": "gcn.circular",
"uuid": "9543fa3f-d5ec-42a8-b723-a512d005859e",
"title": "EP240413a: Upper limits from GECAM-B Observation",
"submitter": "Hop gcn.circular",
"authors": "Yue Wang <m18509381757@163.com>",
"data": {
"date": "24/04/15 04:55:17 GMT",
"from": "Yue Wang <m18509381757@163.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36106"
},
"title": "GCN CIRCULAR",
"number": "36106",
"subject": "EP240413a: Upper limits from GECAM-B Observation"
},
"message_text": "Yue Wang, Shao-Lin Xiong, Chen-wei Wang, Wen-long Zhang, Cheng-kui Li and Chao Zheng, report on behalf of the GECAM team:\n\nGECAM-B was observing normally and covered the sky region of EP240413a (Lian et al., GCN 36086) at event time 2024-04-13T14:39:37 (UTC). The smallest incident angle of GECAM-B GRD detectors is about 21.3 deg for the WXT location (RA\"8.794 deg, Dec=-18.8 deg).\n\nThere was no GECAM-B in-flight trigger around the event time of EP240413a. An automated, blind search for gamma-ray bursts of GECAM-B data found no burst candidates. The targeted search was run within -50 s ~ 250 s around event time, and also identified no counterpart candidates.\n\nWith the three typical GRB spectral models, integration time of 10 s and the WXT localization, the 3-sigma upper-limits of fluence (15 - 300 keV, incident energy) are reported below:\n\nBand model 1 (alpha=-1.9, beta=-3.7, Epp keV): 7.5e-6 erg cm^-2\nBand model 2 (alpha=-1.0, beta=-2.3, Ep#0 keV): 6.6e-6 erg cm^-2\nBand model 3 (alpha=0.0, beta=-1.5, Ep\u001000 keV): 3.5e-6 erg cm^-2\n\nAll measurements above are made with all GRD detectors.\n\nWe note that these results are preliminary and refined analysis will be reported later.\n\nGravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36106.",
"published": "2024-04-15T04:55:23.460312Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-15T04:55:23.460330Z",
"modified": "2024-04-15T04:55:23.467100Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6606,
"topic": "gcn.circular",
"uuid": "59168230-1a58-4184-9168-63969b00991a",
"title": "EP 240414a: BOOTES-4/MET Optical Upper Limits",
"submitter": "Hop gcn.circular",
"authors": "Dingrong Xiong at Yunnan Observatories of CAS, China <xiongdingrong@ynao.ac.cn>",
"data": {
"date": "24/04/16 06:23:58 GMT",
"from": "Dingrong Xiong at Yunnan Observatories of CAS, China <xiongdingrong@ynao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36130"
},
"title": "GCN CIRCULAR",
"number": "36130",
"subject": "EP 240414a: BOOTES-4/MET Optical Upper Limits"
},
"message_text": "D. R. Xiong, J. M. Bai, J. R. Mao, Y. F. Fan, K. Ye, C. J. Wang, Y. X. Xin, B. L. Lun, J. J. Zhang, X. H. Zhao, L. Xu, K. X. Lu, X. Ding, D. Q. Wang (Yunnan Observatories), A. J. Castro-Tirado, E. Fernandez-Garcia, Y. D. Hu (IAA-CSIC) and C. J. Perez del Pulgar (UMA) on behalf of the BOOTES team report:\n\nWe observed the X-ray transient with R.A. = 191.498 deg, DEC = -9.695 deg, and did not found any optical counterpart within an uncertainty of 3 arcmin in radius compared to the PanSTARRS DR1 image. The upper limits of magnitudes (without being corrected for Galactic extinction) are given as follows.\n\nTmid-T0 (day) | UT (start) | Upper Limit (error) | Exposure Time | Filter\n\n--------------------------------------------------------------------------------------------------------------\n\n0.23 | 24-04-14 15:24:00 | 17.446 (0.06) | 60*20s | Clear\n\n-------------------------------------------------------------------------------------------------------------\n\nThe Burst Optical Observer and Transient Exploring System (BOOTES, bootes.iaa.es) is a completed world-wide network of robotic telescopes led at IAA-CSIC (Spain) which aims at following-up transients and other astrophysical sources in the sky for which the first station was installed in 1998 (Castro-Tirado et al. 1999). The fourth station of the BOOTES Network, BOOTES-4/MET, is located at the Lijiang Observatory of the Yunnan Observatories of China (Xiong et al. 2020). See also Hu et al. (2021). We acknowledge the support of BOOTES-4 technical staffs.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36130.",
"published": "2024-04-16T06:24:14.051069Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-16T06:24:14.051084Z",
"modified": "2024-04-16T06:24:14.063913Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6603,
"topic": "gcn.circular",
"uuid": "9af5a795-d462-469f-ad75-13ac489b8513",
"title": "EP240414a: EP-FXT follow-up observation",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/16 04:05:44 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36129"
},
"title": "GCN CIRCULAR",
"number": "36129",
"subject": "EP240414a: EP-FXT follow-up observation"
},
"message_text": "J. Guan, C. K. Li, Y. Chen, S.M. Jia, W. W. Cui, H. Feng, D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA), T. Y. Lian, X. Pan, Z. X. Ling, Y. Liu, H. Sun, D. Y. Li, H. Y. Liu, W. Yuan, C. Zhang (NAOC, CAS) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240414a (Lian et al., GCN 36091) by the Wide-field X-ray Telescope (WXT) of Einstein Probe (EP), we performed an observation with the Follow-up X-ray Telescope (FXT) on board EP. The observation started at 2024-04-14T11:50:01, about 2 hours after the WXT detection, with a net exposure time of 7.2 ks. \n\nAn X-ray source was clearly detected at R.A. = 191.509 deg, Dec. = -9.718 deg, which is R.A. = 12:46:02.16, Dec. = -09:43:04.8, with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). We note that the source is ~8 arcsec away from the optical transient (OT) which is decaying slowly (Aryan et al., GCN 36094; Xu et al., GCN 36105; Jonker et al., GCN 36110). There is no cataloged X-ray source within the error circle. Considering this FXT detected source being within the error circle of the WXT source (1.5 arcmin away) and being likely associated with the OT, we tend to suggest it to be the late-time X-ray emission from EP240414a. The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 3.35e20 cm-2 and a photon index of 1.7(+/-0.3) (90% C.L.). The derived unabsorbed flux in 0.5-10 keV is 3.5(+/-0.8)e-13 erg/s/cm2 (90% C.L.). Assuming this source is indeed associated with EP240414a, its X-ray flux has faded by about 4 orders of magnitude in X-ray flux in about 2 hours since the WXT detection. \n \nPlease note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36129.",
"published": "2024-04-16T04:05:59.537625Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-16T04:05:59.537636Z",
"modified": "2024-04-16T04:05:59.543691Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6561,
"topic": "gcn.circular",
"uuid": "df292521-57a6-49e6-8fac-f51e7013c7ed",
"title": "EP240414a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/14 14:44:16 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36091"
},
"title": "GCN CIRCULAR",
"number": "36091",
"subject": "EP240414a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "T. Y. Lian, X. Pan, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Yang, C. Y. Dai (NJU), Y. F. Liang (PMO), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nWe report on the detection of a fast X-ray transient, desinated EP240414a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient triggered the WXT on-board processing unit at 2024-04-14T09:50:12 (UTC). The position of the source is R.A. = 191.498 deg, DEC = -9.695 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event has a peak flux of ~3 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band.\n\nNo previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. Further information will be provided once the data has been transmitted through a ground station.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36091.",
"published": "2024-04-14T14:44:32.375423Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-14T14:44:32.375437Z",
"modified": "2024-04-14T14:44:32.383187Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6672,
"topic": "gcn.circular",
"uuid": "3576063c-d867-4188-9598-711577532258",
"title": "EP240414a: GMG observation",
"submitter": "Hop gcn.circular",
"authors": "wangbaiting@ynao.ac.cn",
"data": {
"date": "24/04/19 03:57:39 GMT",
"from": "wangbaiting@ynao.ac.cn",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36171"
},
"title": "GCN CIRCULAR",
"number": "36171",
"subject": "EP240414a: GMG observation"
},
"message_text": "B.-T. Wang, R.-Z. Li, J. Mao, H.-C. Feng, J.-M. Bai (YNAO) report:\n\nWe observed the field of EP240414a (Lian et al., GCN 36091) by the 2.4 meter GMG telescope in Yunnan observatories. The observation began from UT 18:42:44.276 April 18, 2024, about 4.4 days from the trigger. A optical countpart was marginally detected. The preliminary results are shown as\n\n-----------------------------------------------------------------------------\nUT exptime\t filter\t mag\n-----------------------------------------------------------------------------\n2024-04-18T18:42:44.276 \t900s\t sdssr\t 20.8 ± 0.3\n-----------------------------------------------------------------------------\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36171.",
"published": "2024-04-19T03:57:53.491950Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-19T03:57:53.491963Z",
"modified": "2024-04-19T03:57:53.497521Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6649,
"topic": "gcn.circular",
"uuid": "12a8b711-943b-4d80-b438-b451c4c1978b",
"title": "EP240414a: GSP detects optical candidate counterpart AT2024gsa",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/04/18 05:19:43 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36154"
},
"title": "GCN CIRCULAR",
"number": "36154",
"subject": "EP240414a: GSP detects optical candidate counterpart AT2024gsa"
},
"message_text": "W. X. Li, S. J. Xue, H. Sun (NAOC), X. F. Wang (THU), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report the optical follow-up observations of AT2024gsa (Aryan et al., GCN 36094, Xu et al., GCN 36105, Srivastav et al. GCN 36150). This transient was identified as the optical counterpart to the fast X-ray transient EP240414a (Lian et al., GCN 36091; Guan et al., GCN 36129).\n\nOur observations were conducted on 2024 April 18.065 UT using the 1-meter telescope at the Las Cumbres Observatory node located at Cerro Tololo Interamerican Observatory in Chile. AT2024gsa is detected in all BVgri band images.\nThe photometric results are:\nB ~ 21.3m\nV ~ 20.9m\ng ~ 21.1m\nr ~ 20.7m\ni ~ 20.6m\n\nFurther followup observations are encouraged.\n\nThese observations were taken as part of the Global Supernova Project.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36154.",
"published": "2024-04-18T05:20:07.889567Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-18T05:20:07.889583Z",
"modified": "2024-04-18T05:20:07.898982Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6564,
"topic": "gcn.circular",
"uuid": "50cd6d46-c505-4fa7-b1fc-f82d25e5204b",
"title": "EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3",
"submitter": "Hop gcn.circular",
"authors": "Janet Chen at National Central University <janetstars@gmail.com>",
"data": {
"date": "24/04/14 17:15:21 GMT",
"from": "Janet Chen at National Central University <janetstars@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36094"
},
"title": "GCN CIRCULAR",
"number": "36094",
"subject": "EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3"
},
"message_text": "A. Aryan (NCUIA), S. Yang (HNAS), T.-W. Chen, W.-J. Hou, C.-H. Lai, A. Sankar.K, Y.-C. Pan (all NCUIA), S. J. Smartt (Oxford/QUB), K. W. Smith (QUB), H.-Y. Hsiao, M.-H. Lee, C.-C. Ngeow, C.-S. Lin, H.-C. Lin, J.-K. Guo (all NCUIA), J. Gillanders, L. Rhodes, S. Srivastav (all Oxford), T. Moore and M. Fulton (both QUB) report:\n\nWe observed the field of EP240414a (Lian et al., GCN 36091) using the Lulin One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen et al., AstroNote 2021-92). The first LOT epoch of observations started at 12:50 UT on 14 of April 2024 (MJD`414.535), 3.13 hours after the EP trigger.\n\nWe used the Kinder pipeline (Yang et al. A&A 646, A22) to stack the images and subtract the stacked images with the Legacy Survey DR10 template images. We detected an optical transient candidate in the difference image, at RA\u0012:46:01.7248, Dec=-9:43:08.872 (which is 1.56 arcmins away from the reported coordinate of EP240414a). We note an extended source in the Legacy Survey image, which is likely its host galaxy. We cross-matched it with the SDSS DR15 catalogue and found it could correspond to the galaxy, SDSS J124601.99-094309.3, with r-band magnitude as 19.04 mag.\n\nThe details of the observations and measured PSF magnitudes (in the AB system) of the possible counterpart of EP240414a are as follows:\n\nTelescope | Filter | MJD | t-t0 | Exposure | Magnitude | Seeing | Airmass\nLOT | r | 60414.535 | 3.13 hrs | 300 sec * 6 | 21.52 +/- 0.12 | 1\".7 | 1.31\nLOT | i | 60414.564 | 3.68 hrs | 300 sec * 6 | 21.40 +/- 0.16 | 1\".2 | 1.43\n\nThe presented magnitudes are calibrated using the field stars from the SDSS catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.03 mag in the direction of the burst (Schlafly & Finkbeiner 2011).\n\nAccordint to SDSS, for the likely host galaxy, SDSS J124601.99-094309.3, its photo-z is 0.299 +/- 0.0426, and the distance module is then 40.80. Assuming r-band can be roughly k-corrected to g-band, with the Milky Way extinction correction, the optical counterpart candidate has the rest-frame M_g = -19.07 mag and M_r = -19.18 mag.\n\nWe are still continuously observing this source. Further follow-up observations are encouraged to identify the nature of this X-ray transient.\n\nWe thank the Einstein Probe team for useful communication.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36094.",
"published": "2024-04-14T17:15:37.439097Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-14T17:15:37.439154Z",
"modified": "2024-04-14T17:15:37.447191Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6741,
"topic": "gcn.circular",
"uuid": "663f023f-0fa6-41d3-97c5-4bb00ec26275",
"title": "EP240414a: Near-IR observations with NIRES and WINTER",
"submitter": "Hop gcn.circular",
"authors": "Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com>",
"data": {
"date": "24/04/20 04:42:12 GMT",
"from": "Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36189"
},
"title": "GCN CIRCULAR",
"number": "36189",
"subject": "EP240414a: Near-IR observations with NIRES and WINTER"
},
"message_text": "Viraj Karambelkar (Caltech), Kaew Tinyanont (NARIT), Sam Rose (Caltech),\nTomas Ahumada (Caltech), Robert Stein (Caltech), Nathan Lourie (MIT),\nDanielle Frostig (MIT), Geoffrey Mo (MIT), Robert Simcoe (MIT), Mansi\nKasliwal (Caltech)\n\nWe observed the location of the X-ray transient EP240414a (Lian et al., GCN\n36091) in the K-prime band with the NIRES acquisition camera on the Keck II\ntelescope starting at UTC 2024-04-19T08:15:11. Our observations lasted for\n100 seconds (25 sec, 4 coadds).\n\nWe detect the optical counterpart (GCN 36094, 36105, 36110, 36130, 36150,\n36154, 36171, 36187) in the near-infrared Kp-band with m_Kp ~ 19.8 +/- 0.1\nmag (AB). This suggests an r - Kp color of ~ 1 mag, based on r-band\nphotometry from 0.7 days earlier (reported in Wang et al. GCN #36171).\n\nWe also observed the location with the WINTER camera on the Palomar 40-inch\ntelescope (Lourie et al. 2021) in the J-band on UTC 2024-04-24T06:22:01 and\ndid not detect the source to a limit of m_J ~ 19 mag (AB).\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36189.",
"published": "2024-04-20T04:42:29.194062Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-20T04:42:29.194090Z",
"modified": "2024-04-20T04:42:29.200233Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6575,
"topic": "gcn.circular",
"uuid": "0f94cc4c-995a-409d-85c5-05c39a074217",
"title": "EP 240414a: NOT optical counterpart confirmation",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/04/15 04:54:28 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36105"
},
"title": "GCN CIRCULAR",
"number": "36105",
"subject": "EP 240414a: NOT optical counterpart confirmation"
},
"message_text": "D. Xu (NAOC), D.B. Malesani (DAWN/NBI & Radboud), P. Jonker (Radboud), Z.P. Zhu, X. Liu, S.Y. Fu, S.Q. Jiang, J. An, T.H. Lu (NAOC), M. Turkki (U. of Helsinki, NOT) report on behalf of a large collaboration:\n\nWe observed the field of the X-ray transient detected by Einstein Probe, EP 240414a, using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 22:07:38UT on 2024-04-14, i.e., 12.29 hr after the EP trigger and 5 x 300 s r-band frames were obtained.\n\nThe previously reported optical counterpart candidate by LOT (Aryan et al., GCN 36094) is clearly detected in our stacked image with coordinates\n\nR.A. = 12:46:01.67 (J2000)\nDec. = -09:43:08.8 (J2000)\n\nwhich has r = 21.9 +/- 0.1 (AB) at a median time of 0.521 day post-trigger. Comparison of the two observations shows that the source was decaying slowly.\n\nWe also searched for other potential counterparts in the NOT image which covers most of the EP/WXT error region, and didn't find any other credible candidate via image subtraction.\n\nWe thus confirm that the LOT candidate is the optical counterpart of EP 240414a.\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36105.",
"published": "2024-04-15T04:54:43.381354Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-15T04:54:43.381376Z",
"modified": "2024-04-15T04:54:43.390499Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6637,
"topic": "gcn.circular",
"uuid": "cc2d640e-d101-4a2d-bd17-26ec91d7e552",
"title": "EP240414a: Pan-STARRS detects re-brightening of the candidate counterpart AT2024gsa",
"submitter": "Hop gcn.circular",
"authors": "S. Srivastav at Oxford <shubhamsrivastav@gmail.com>",
"data": {
"date": "24/04/17 18:13:16 GMT",
"from": "S. Srivastav at Oxford <shubhamsrivastav@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36150"
},
"title": "GCN CIRCULAR",
"number": "36150",
"subject": "EP240414a: Pan-STARRS detects re-brightening of the candidate counterpart AT2024gsa"
},
"message_text": "S. Srivastav, J. H. Gillanders, L. Rhodes (Oxford), S. J. Smartt (Oxford/QUB), T.-W. Chen (NCU), M. Huber, K. C. Chambers (IfA), M. Fulton, K. W. Smith (QUB) report on behalf of a larger collaboration:\n\nWe report optical follow-up observations of AT2024gsa (Aryan et al., GCN 36094; Chen et al. TNS Astronomical Transient Report No. 207843), the candidate optical counterpart to the fast X-ray transient EP240414a (Lian et al., GCN 36091; Guan et al., GCN 36129). AT2024gsa was reported to be decaying in the optical (Xu et al., GCN 36105).\n\nWe observed AT2024gsa with the 1.8-m Pan-STARRS1 telescope in iz-bands on 2 epochs, with observations starting on MJDs 60416.4 and 60417.4, corresponding to ~2.0 and ~3.0 days post-discovery of the X-ray transient. Our PS1 photometry shows the transient has brightened from 22.2 +/- 0.3 (on MJD 60416.4) to 20.9 +/- 0.06 (on MJD 60417.4) in the i-band, suggesting a rise of ~1.3 mag/day. A similar rise was also seen in the z-band.\n\nAssuming AT2024gsa is associated with the potential host galaxy SDSS J124601.99-094309.3 at z=0.41 (Jonker et al., GCN 36110), the transient currently has an absolute rest-frame r-band magnitude of ~ -21. Further followup observations are encouraged.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36150.",
"published": "2024-04-17T18:13:35.938542Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-17T18:13:35.938566Z",
"modified": "2024-04-17T18:13:35.948298Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6698,
"topic": "gcn.circular",
"uuid": "6021fdb3-0001-4a6a-ade2-5088d84e17c9",
"title": "EP240414A: Terskol Zeiss-2000 optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"data": {
"date": "24/04/19 17:52:39 GMT",
"from": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36187"
},
"title": "GCN CIRCULAR",
"number": "36187",
"subject": "EP240414A: Terskol Zeiss-2000 optical upper limit"
},
"message_text": "S. Belkin (IKI), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:\n\nWe observed the EP240414A (Lian et al., GCN 36091) with the Zeiss-2000 telescope of Terskol observatory in R-filter on 2024-04-15 starting (UT) 22:55:21. We did not detect the optical counterpart (Aryan et al., GCN 36094; Xu et al., GCN 36105; Jonker et al., GCN 36110; Xiong et al., 36130; Srivastav et al., GCN 36150; Li et al., GCN 36154; Wang et al., GCN 36171;) down to the limiting magnitude of R~22.0. Preliminary photometry of a stacked image is the following\n\nDate UT start t-T0 Exp. Filter OT Err. UL(3sigma)\n (mid, days) (s)\n\n2024-04-15 22:55:21 1.56347 35x90 R n/d n/d 22.0\n\nThe photometry is based on nearby USNO-B1.0 stars.\nUSNO-B1.0\nRA DEC R2\n12:46:00.7214400 -09:43:21.021600 17.15\n12:45:53.8893600 -09:43:46.700400 15.87\n12:46:03.7461600 -09:41:28.521600 15.12\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36187.",
"published": "2024-04-19T17:52:54.430552Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-19T17:52:54.430565Z",
"modified": "2024-04-19T17:52:54.438318Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6650,
"topic": "gcn.circular",
"uuid": "c051aae3-a720-4749-b8db-bb5ccfa2fa8c",
"title": "EP240416a: BOOTES-2/TELMA Optical Upper Limit",
"submitter": "Hop gcn.circular",
"authors": "Dingrong Xiong at Yunnan Observatories of CAS, China <xiongdingrong@ynao.ac.cn>",
"data": {
"date": "24/04/18 09:25:48 GMT",
"from": "Dingrong Xiong at Yunnan Observatories of CAS, China <xiongdingrong@ynao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36155"
},
"title": "GCN CIRCULAR",
"number": "36155",
"subject": "EP240416a: BOOTES-2/TELMA Optical Upper Limit"
},
"message_text": "D. R. Xiong, J. M. Bai, J. R. Mao, Y. F. Fan, K. Ye, C. J. Wang, Y. X. Xin, B. L. Lun, J. J. Zhang, X. H. Zhao, L. Xu, K. X. Lu, X. Ding, X. G. Yu, D. Q. Wang, S. S. He, X. L. Zhang, J. G. Wang (Yunnan Observatories/CAS), A. J. Castro-Tirado, E. Fernandez-Garcia, Y. D. Hu (IAA-CSIC) and C. J. Perez del Pulgar (UMA) on behalf of the BOOTES team report:\n\nWe observed the X-ray transient EP 240416a (Cheng et al., GCN 36138), and did not found any optical counterpart within an uncertainty of 3 arcmin in radius compared to the PanSTARRS DR1 image. The upper limits of magnitudes (without being corrected for Galactic extinction) are given as follows.\n\nTmid-T0 (day) | UT (start) | Upper Limit (error) | Exposure Time | Filter\n\n--------------------------------------------------------------------------------------------------------------\n\n0.96 | 24-04-17T01:50:42 | 19.56 (0.2) | 100s*10 | Clear\n\n-------------------------------------------------------------------------------------------------------------\n\nThe Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998 (Castro-Tirado et al. 1999; Hu et al. 2021). The BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain). We acknowledge the support of these staffs from the BOOTES telescope networks.\n\n=================================================================\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36155.",
"published": "2024-04-18T09:26:07.182990Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-18T09:26:07.183002Z",
"modified": "2024-04-18T09:26:07.190543Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6620,
"topic": "gcn.circular",
"uuid": "73ccc9e8-c224-4945-aea8-018ffc3b858f",
"title": "EP240416a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/16 16:41:11 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36138"
},
"title": "GCN CIRCULAR",
"number": "36138",
"subject": "EP240416a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "H. Q. Cheng, W. X. Wang, W. Yuan, Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, T. Y. Lian, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, X. Pan, H. Sun, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA), on behalf of the Einstein Probe team\n\nWe report on the detection of a fast X-ray transient EP240416a at 2024-04-16T02:42:13 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The position of the source is R.A. = 203.150 deg, DEC = -13.612 deg (J2000) with an uncertainty of 3 arcmin (radius, 90% C.L. statistical and systematic). The flare lasted for at least 200 seconds, with the tail of the fading light curve undetected due to the interruption of the observation. The peak flux reached ~1.3 x 10^-9 erg/s/cm^2 in the 0.5-4.0 keV band. The averaged 0.5-4.0 keV spectrum can be fitted with an absorbed power law (with the column density fixed at the Galactic value of 4.0 x 10^20 cm^-2) with a photon index of 1.5(-0.6/+0.6). The derived average unabsorbed 0.5-4.0 keV flux is 5.0(-1.6/+2.6) x 10^-10 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.\n \nNo previously known bright X-ray sources are found within the error circle around the source position. The derived source parameters may be subject to larger uncertainties than those quoted here since the in-orbit calibration of the instrument is still in progress.\n\nFurther follow-up observations are encouraged to identify the nature of this X-ray transient.\n\nThe above observation was made with EP-WXT during the commissioning phase. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36138.",
"published": "2024-04-16T16:41:27.276152Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-16T16:41:27.276165Z",
"modified": "2024-04-16T16:41:27.285627Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6675,
"topic": "gcn.circular",
"uuid": "f5a38059-4dd5-420e-8d8d-2e3a5b604efc",
"title": "EP240416a: J-band observations with WINTER",
"submitter": "Hop gcn.circular",
"authors": "Geoffrey Mo at MIT <gmo@mit.edu>",
"data": {
"date": "24/04/19 05:07:16 GMT",
"from": "Geoffrey Mo at MIT <gmo@mit.edu>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36172"
},
"title": "GCN CIRCULAR",
"number": "36172",
"subject": "EP240416a: J-band observations with WINTER"
},
"message_text": "Geoffrey Mo (MIT), Viraj Karambelkar (Caltech), Danielle Frostig (MIT), Robert Stein (Caltech), Nathan Lourie (MIT), Tomas Ahumada (Caltech), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:\n\nWe observed the field of the EP-WXT X-ray transient EP240416a (Cheng et al., GCN 36138) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1 square degree WINTER camera (Lourie et al. 2020).\n\nObservations began at 2024-04-17T14:01:04.438 UTC (~1.5 days after the X-ray transient) and consisted of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar).\n\nWe do not detect the optical counterpart discovered by Kinder and confirmed by Xinglong and NOT (Chen et al., GCN 36139, An et al., GCN 36144, Antipov et al., GCN 36142, Xiong et al., GCN 36155, Pankov et al., GCN 36157, Belkin et al., GCN 36158), setting the following upper limit: J ~ 19.4 mag (AB).\n\nWINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucille Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36172.",
"published": "2024-04-19T05:07:33.057578Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-19T05:07:33.057593Z",
"modified": "2024-04-19T05:07:33.067859Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6652,
"topic": "gcn.circular",
"uuid": "cf11fba0-07ce-4a36-8fb6-8315a0a140fb",
"title": "EP240416A: Khureltogoot optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"data": {
"date": "24/04/18 12:29:15 GMT",
"from": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36157"
},
"title": "GCN CIRCULAR",
"number": "36157",
"subject": "EP240416A: Khureltogoot optical upper limit"
},
"message_text": "N. Pankov (HSE,IKI), L. Elenin (KIAM), A. Pozanenko (IKI), N. Tungalag (IAG), A. Volnova (IKI), S. Belkin (IKI) report on behalf of GRB IKI FuN:\n\nWe observed the EP240416A (Cheng et al., GCN 36138) with the ORI-40 telescope of Khureltogoot observatory in Clear filter starting on 2024-04-16 (UT) 17:57:07. We did not detect the optical counterpart (Chen et al., GCN 36139; An et al., GCN 36144). Preliminary photometry of a stacked image is the following\n\nDate UT start t-T0 Exp. Filter OT Err. UL(3sigma)\n (mid, days) (s)\n\n2024-04-16 17:57:07 0.65409 54*60 Clear n/d n/d 19.7\n\nThe photometry is based on nearby USNO-B1.0 (R2) stars.\n\nThe given results is in agreement with the upper limit obtained by (Xiong et al., GCN 36155).\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36157.",
"published": "2024-04-18T12:29:32.176958Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-18T12:29:32.176973Z",
"modified": "2024-04-18T12:29:32.184744Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6622,
"topic": "gcn.circular",
"uuid": "bafbc285-8c6d-49b8-8a81-4a9468f3526f",
"title": "EP240416a: Kinder optical counterpart candidate",
"submitter": "Hop gcn.circular",
"authors": "Janet Chen at National Central University <janetstars@gmail.com>",
"data": {
"date": "24/04/16 19:39:25 GMT",
"from": "Janet Chen at National Central University <janetstars@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36139"
},
"title": "GCN CIRCULAR",
"number": "36139",
"subject": "EP240416a: Kinder optical counterpart candidate"
},
"message_text": "T.-W. Chen, A. Aryan (both NCUIA), S. Yang (HNAS), S. J. Smartt (Oxford/QUB), M. Fulton (QUB), W.-J. Hou, H.-Y. Hsiao, C.-H. Lai, Y.-C. Pan, A. Sankar.K, M.-H. Lee, C.-C. Ngeow, C.-S. Lin, H.-C. Lin, J.-K. Guo (all NCUIA), J. Gillanders, L. Rhodes, S. Srivastav, H. F. Stevance (all Oxford), T. Moore and K. W. Smith (both QUB) report:\n\nWe observed the field of EP240416a (Cheng et al., GCN 36138) using the Lulin One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen et al., AstroNote 2021-92). The first LOT epoch of observations started at 16:51 UT on 16 of April 2024 (MJD = 60416.702), 14.15 hours after the EP trigger.\n\nWe used the Kinder pipeline (Yang et al. A&A 646, A22) to stack the images and subtract the stacked images with the PanSTARRS1 template images. We detected an optical transient in the difference image, at RA = 13:32:34.514, Dec = -13:37:49.05 (which is 69.6 arcsec away from the reported coordinate of EP240416a by Cheng et al. GCN 36138).\n\nThe details of the observations and measured PSF magnitudes (in the AB system) of the possible counterpart of EP240416a are as follows:\n\nTelescope | Filter | MJD | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass\nLOT | g | 60416.702 | 14.15 hrs | 300 sec * 7 | 22.39 +/- 0.12 | 1\".4 | 1.86\nLOT | r | 60416.707 | 14.27 hrs | 300 sec * 7 | 22.08 +/- 0.12 | 1\".3 | 1.40\nLOT | i | 60416.711 | 14.36 hrs | 300 sec * 7 | 22.02 +/- 0.16 | 1\".3 | 1.54\n\nThe MJD reported is the start time of the first observation in each band. We observed in a sequence of 300 sec in g,r and i, then 6x300 in r, i, g. All measurements were made on the 7-frame co-adds. The presented magnitudes are calibrated using the field stars from the PanSTARRS1 catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.05 mag in the direction of the burst (Schlafly & Finkbeiner 2011).\n\nFurther follow-up observations are encouraged to identify the nature of this X-ray transient.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36139.",
"published": "2024-04-16T19:39:45.629115Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-16T19:39:45.629128Z",
"modified": "2024-04-16T19:39:45.639691Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6625,
"topic": "gcn.circular",
"uuid": "db34bd74-e783-4fb6-b47d-cf2bb2e3d8e5",
"title": "EP240416A: MASTER optical observations",
"submitter": "Hop gcn.circular",
"authors": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"data": {
"date": "24/04/16 22:50:31 GMT",
"from": "Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36142"
},
"title": "GCN CIRCULAR",
"number": "36142",
"subject": "EP240416A: MASTER optical observations"
},
"message_text": "G.Antipov, V.Lipunov, P.Balanutsa (Lomonosov MSU), D.Buckley (SAAO), K.Zhirkov,A.Kuznetsov,\nN.Tiurina, E.Gorbovskoy, Ya.Kechin, D.Vlasenko, Yu.Tselik,I.Gorbunov,\nV.Vladimirov,D.Zimnukhov, V.Senik, A.Yudin,A.Chasovnikov, D.Cheryasov(Lomonosov MSU,SAI,PhysicsDepartment),\nO.Gress,N.Budnev(ISU),\nA.Sosnovskij (Crimean Astrophysical Observatory, RAS),\nC.Francile. F. Podesta, R.Podesta (Observatorio Astronomico Felix AguilarOAFA),\nR. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),\nA. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),\nA. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)\n\nMASTER Global robotic net (http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)\nstarted EP 240416A (Cheng et al. #GCN 36138, Triggertime= 2024-04-16 02:42:13UT,\nNotice 24-04-16T16:41:11, Center R.A.,Dec. = 203.150 -13.612)\noptical (unfiltered) observation at 3 MASTER observatories.\n\n\nMASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to EP240416A error-box\n66152 sec after trigger time at 2024-04-16 21:04:45 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 56 deg. The sun altitude is -36.6 deg.\n\nMASTER-Tavrida robotic telescope located in Russia was pointed to the EP errorbox 66334 sec after trigger time at 2024-04-16 21:07:47 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 57 deg. The sun altitude is -35.0 deg.\n\nMASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the EP Alert 240416.11 errorbox 67795 sec after trigger time at 2024-04-16 21:32:08 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 22 deg. The sun altitude is -63.6 deg.\n\nThe galactic latitude b = 48 deg., longitude l = 319 deg.\n\nThere is no OT (Chen et al. #GCN 36139) in MASTER database since 2003y, that can confirm Kinder optical afterglow.\n\nObservation and analysis will be continued.\nWe obtained the following upper limits.\n\nTmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____________________|____________________________________|_____|_______|_______|________\n 66213 | 2024-04-16 21:04:45 | MASTER-Kislovodsk | (13h 33m 04.43s , -13d 07m 01.2s) | C | 120 | 18.1 |\n 66333 | 2024-04-16 21:04:45 | MASTER-Kislovodsk | (13h 33m 04.43s , -13d 07m 01.2s) | C | 360 | 18.8 | Coadd\n 67353 | 2024-04-16 21:04:45 | MASTER-Kislovodsk | (13h 33m 04.43s , -13d 07m 01.2s) | C | 2400 | 19.4 | Coadd\n 66213 | 2024-04-16 21:04:45 | MASTER-Kislovodsk | (13h 33m 03.54s , -13d 30m 11.3s) | C | 120 | 17.7 |\n 66333 | 2024-04-16 21:04:45 | MASTER-Kislovodsk | (13h 33m 03.54s , -13d 30m 11.3s) | C | 360 | 18.7 | Coadd\n 67353 | 2024-04-16 21:04:45 | MASTER-Kislovodsk | (13h 33m 03.53s , -13d 30m 11.2s) | C | 2400 | 19.4 | Coadd\n 66353 | 2024-04-16 21:07:05 | MASTER-Kislovodsk | (13h 32m 58.66s , -13d 30m 51.0s) | C | 120 | 18.1 |\n 66353 | 2024-04-16 21:07:05 | MASTER-Kislovodsk | (13h 32m 59.58s , -13d 07m 40.7s) | C | 120 | 18.2 |\n 66395 | 2024-04-16 21:07:47 | MASTER-Tavrida | (13h 32m 43.07s , -12d 57m 28.7s) | C | 120 | 14.9 |\n 66493 | 2024-04-16 21:09:26 | MASTER-Kislovodsk | (13h 32m 57.78s , -13d 29m 55.6s) | C | 120 | 18.1 |\n 66493 | 2024-04-16 21:09:26 | MASTER-Kislovodsk | (13h 32m 58.79s , -13d 06m 45.2s) | C | 120 | 18.2 |\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36142.",
"published": "2024-04-16T22:50:49.611465Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-16T22:50:49.611487Z",
"modified": "2024-04-16T22:50:49.620227Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6653,
"topic": "gcn.circular",
"uuid": "2439a266-477b-4f18-8e51-f384afeb62d2",
"title": "EP240416A: Terskol Zeiss-2000 optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"data": {
"date": "24/04/18 12:40:39 GMT",
"from": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36158"
},
"title": "GCN CIRCULAR",
"number": "36158",
"subject": "EP240416A: Terskol Zeiss-2000 optical upper limit"
},
"message_text": "S. Belkin (IKI), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:\n\nWe observed the EP240416A (Cheng et al., GCN 36138) with the Zeiss-2000 telescope of Terskol observatory in R-filter starting on on 2024-04-16 (UT) 21:21:18. We did not detect the optical counterpart (Chen et al., GCN 36139; An et al., GCN 36144) down to the limiting magnitude of R~21.9. Preliminary photometry of a stacked image is the following\n\nDate UT start t-T0 Exp. Filter OT Err. UL(3sigma)\n (mid, days) (s)\n\n2024-04-16 21:21:18 0.79832 70x90 R n/d n/d 21.9\n\nThe photometry is based on nearby USNO-B1.0 stars.\nUSNO-B1.0\nRA DEC R2\n13:32:30.1848000 -13:36:51.350400 13.67\n13:32:25.6521600 -13:39:02.671200 14.26\n13:32:19.2355200 -13:39:27.943200 13.96\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36158.",
"published": "2024-04-18T12:40:59.224238Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-18T12:40:59.224256Z",
"modified": "2024-04-18T12:40:59.230283Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6627,
"topic": "gcn.circular",
"uuid": "86d5c121-2be1-49b5-b145-f50b86bd04a5",
"title": "EP 240416a: Xinglong and NOT decaying optical counterpart",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/04/17 07:45:53 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36144"
},
"title": "GCN CIRCULAR",
"number": "36144",
"subject": "EP 240416a: Xinglong and NOT decaying optical counterpart"
},
"message_text": "J. An, X. Liu, S.Q. Jiang, Z.P. Zhu, J. Zheng, S. Liu, J.J. Jin, S.Y. Fu, T.H. Lu, Z. Fan, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI) report on behalf of a large collaboration:\n\nWe observed the field of the X-ray transient, EP 240416a, detected by EP/WXT (Cheng et al., GCN 36138) using the 2.16-m telescope located at Xinglong, Hebei, China. We obtained 5 x 360 s R-band frames with a median time of 2024-04-16T17:18:06, i.e., 14.6 hr after the EP trigger.\n\nThe stacked R-band image has a limiting magnitude of R ~ 22 mag, calibrated with the PanSTAR field. Inspection of the whole EP/WXT 3 arcmin error circle produces a few low S/N optical counterpart candidates.\n\nWe subsequently performed r-band photometry at the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera, and obtained 3 x 300 s frames in the Sloan r-band with a median time of 2024-04-17T01:00:00, i.e., 22.3 hr after the EP trigger.\n\nThe stacked r-band image has a limiting magnitude of r ~ 23.5 mag, calibrated with the PanSTAR field. Inspection of the whole EP/WXT 3 arcmin error circle also produces a few optical counterpart candidates.\n\nThe candidates from the two epochs are corssmatched in position and only one single optical transient (OT) is left. It is localized at\n\nR.A. = 13:32:34.51 (J2000)\nDec. = -13:37:48.88 (J2000)\n\nwith an uncertainty of radius ~ 0.3 arcsec, being consistent with the candidate reported by Kinder (Chen et al., GCN 36139). This OT has m(R) = 21.8 +/- 0.4 (Vega) in the Xinglong image and decayed to m(r) = 22.66 +/- 0.18 (AB) in the NOT image, calibrated with the PanSTARRS field. The decay rate is consistent with that for typical GRB optical afterglows.\n\nTherefore, we suggest that the OT is very likely the optical counterpart of EP 240416a, which is likely a GRB event.\n\n\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36144.",
"published": "2024-04-17T07:46:09.889055Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-17T07:46:09.889069Z",
"modified": "2024-04-17T07:46:09.897263Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6658,
"topic": "gcn.circular",
"uuid": "10a65f4d-c44f-4f1d-aa80-7665fbd826f8",
"title": "EP240417a: EP-WXT detection of a fast X-ray transient ",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/18 16:56:42 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36161"
},
"title": "GCN CIRCULAR",
"number": "36161",
"subject": "EP240417a: EP-WXT detection of a fast X-ray transient "
},
"message_text": "J. W. Hu, W. Chen, S. Q. Jiang, C. C. Jin, Y. Liu, Z. X. Ling, C. Zhang, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, T. Y. Lian, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA), on behalf of the Einstein Probe team. \n\nWe report on the detection of a fast X-ray transient EP240417a at 2024-04-17T15:12:33 (UTC) by the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe (EP) mission during a calibration observation. The position of the source is R.A. = 177.442 deg, DEC = -15.438 deg (J2000) with an uncertainty of 3 arcmin (radius, 90% C.L. statistical and systematic). The flare lasted for at least 1500 seconds, with the tail of the fading light curve undetected due to the interruption of the observation. The peak flux reached ~3 x 10^-10 erg/s/cm^2 in the 0.5-4.0 keV band. The averaged 0.5-4.0 keV spectrum can be well fitted with a single power law of photon index 1.15(-0.26/+0.27), and the best-fit absorption column density is consistent with 0. The derived average 0.5-4.0 keV flux is 9.8(-0.8/+0.8) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.\n \nNo previously known bright X-ray sources are found within the error circle around the source position. The derived source parameters may be subject to larger uncertainties than those quoted here since the in-orbit calibration of the instrument is still in progress.\n\nFurther follow-up observations are encouraged to identify the nature of this X-ray transient.\n\nThe above observation was made with EP-WXT during the commissioning phase. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36161.",
"published": "2024-04-18T16:57:00.645726Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-18T16:57:00.645738Z",
"modified": "2024-04-18T16:57:00.652965Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6795,
"topic": "gcn.circular",
"uuid": "864d0ead-1ed6-4552-9bcb-c4ffcde4293d",
"title": "EP240417a: no counterpart detection by SOAR",
"submitter": "Hop gcn.circular",
"authors": "JONATHAN QUIROLA VASQUEZ <jaquirola@uc.cl>",
"data": {
"date": "24/04/21 16:01:11 GMT",
"from": "JONATHAN QUIROLA VASQUEZ <jaquirola@uc.cl>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36211"
},
"title": "GCN CIRCULAR",
"number": "36211",
"subject": "EP240417a: no counterpart detection by SOAR"
},
"message_text": "J. Quirola-Vásquez (Radboud Univ.), F. E. Bauer (PUC), P.G. Jonker (Radboud Univ.), A. J. Levan (Radboud Univ. & Warwick Univ.), D. B. Malesani (DAWN/NBI and Radboud Univ.) on behalf of a larger collaboration:\n\nWe observed the field of the Einstein Probe fast X-ray transient EP240417a (Hu et al., GCN 36161) with the SOAR telescope of Cerro Pachón observatory on 2024-04-20 starting (UT) 00:22:04.167, i.e., ~2.4 days after the X-ray trigger. We took 2 images using the Goodman Spectrograph RedCam in imaging mode, and the i-SDSS filter, with a total exposure time of 1100 seconds. We did not detect an optical counterpart in the field of EP240417a (R.A. = 177.442 deg and DEC = -15.438 deg, with an uncertainty of 3 arcmin) down to the limiting magnitude of i~23 AB mag. None new detection or >2sigma variability regarding the Legacy catalog. We used the PanSTARRS catalog as the magnitude reference for calibration.\n\nWe acknowledge the excellent support from the SOAR staff.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36211.",
"published": "2024-04-21T16:01:27.574163Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T16:01:27.574181Z",
"modified": "2024-04-21T16:01:27.583612Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6683,
"topic": "gcn.circular",
"uuid": "fb759362-ce0a-4206-a45f-f48724444537",
"title": "EP240417a: YAHPT Optical Upper Limits",
"submitter": "Hop gcn.circular",
"authors": "Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>",
"data": {
"date": "24/04/19 11:17:05 GMT",
"from": "Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36178"
},
"title": "GCN CIRCULAR",
"number": "36178",
"subject": "EP240417a: YAHPT Optical Upper Limits"
},
"message_text": "Tian-Rui Sun, Jin-Jun Geng, Jian Chen, Yan-Long Hua and Lei Hu report on behalf of the YAHPT team:\n\nFollowing the detection of EP240417a by Einstein Probe (Hu et al., GCN 36161),\nwe use the Yaoan High Precision Telescope at Yaoan Astronomy Observation Station (Yunnan province, China) to search and follow up.\n\nWe observed the target position with 300s exposure in Rc-band starting from 2024-04-18T16:35:20.400 about.\nWe took 5 images with total exposure time of 1500 seconds from 16:35:20 to 16:55:30.\nWe did not detect any possible optical counterpart up to Rc = 20.7 within the 3-arcmin radius.\n\nWe used the USNO B1.0 catalog (R2mag) as the magnitude reference for calibration.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36178.",
"published": "2024-04-19T11:17:12.599497Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-19T11:17:12.599509Z",
"modified": "2024-04-19T11:17:12.605040Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6777,
"topic": "gcn.circular",
"uuid": "747d90a8-6399-4315-8115-5b6038cab5af",
"title": "EP240420a: detection of fading X-ray emission with refined position by EP-FXT ",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/21 05:26:43 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36203"
},
"title": "GCN CIRCULAR",
"number": "36203",
"subject": "EP240420a: detection of fading X-ray emission with refined position by EP-FXT "
},
"message_text": "D. W. Han (IHEP, CAS), W. J. Zhang (NAOC, CAS), C. K. Li, Y. Chen, S. M. Jia, W. W. Cui, J. Guan, H. Feng, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), P. Friedrich, V. Burwitz, N. Meidinger, K. Nandra, A. Rau (MPE), B. Cordier (CEA), S. X. Wen, W. X. Wang, Z. X. Ling, Y. Liu, H. Sun, D. Y. Li, H. Y. Liu, W. Yuan, C. Zhang (NAOC, CAS) on behalf of the Einstein Probe team\n\n\nFollowing the detection of the fast X-ray transient EP240420a (Zhang et al., GCN 36194) by the Wide-field X-ray Telescope (WXT) on board Einstein Probe (EP), we performed an observation with EP's Follow-up X-ray Telescope (FXT). The observation started at 2024-04-20T14:05:01, about 2 hours after the WXT detection of the X-ray flare, with a net exposure time of 7.1ks.\n\nAn X-ray source was clearly detected at R.A. = 228.7291 deg, Dec. =14.8024 deg (R.A. = 15:14:54.98, Dec = 14:48:08.6), with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is 1 arcmin away from the reported WXT position of EP240420a. There is no cataloged X-ray source within the error circle. The FXT count rate of the source has dropped by a factor of 50% over the observation duration of 14 ks. Considering this source being within the error circle of the WXT transient and being fading away, we suggest it being the late-time X-ray emission from EP240420a.The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 2.5e20 cm-2 and a photon index of 1.9(+/-0.1). The derived unabsorbed flux in 0.5-10 keV is 1.2(+/-0.1)e-12 erg/s/cm2. Assuming this source is indeed associated with EP240420a, its X-ray flux has faded by about more than 3 orders of magnitude in X-ray flux since the WXT detection. The quoted errors above are at the 90% confidence level. \n\nPlease note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. Launched 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. \n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36203.",
"published": "2024-04-21T05:26:57.875338Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T05:26:57.875370Z",
"modified": "2024-04-21T05:26:57.884029Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6749,
"topic": "gcn.circular",
"uuid": "dec057a2-cd52-4ff1-b846-105213c88bd7",
"title": "EP240420a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/20 14:22:52 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36194"
},
"title": "GCN CIRCULAR",
"number": "36194",
"subject": "EP240420a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "W. J. Zhang (NAOC, CAS), Y. J. Zhang (THU), S. X. Wen, W. X. Wang, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, T. Y. Lian, H. Y. Liu, M. J. Liu, Z. Z. Lv, X. Mao, H. W. Pan, X. Pan, H. Sun, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n \nSubjects: X-ray, Transient\n \nWe report on the detection of a fast X-ray transient, designated EP240420a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient triggered the WXT on-board processing unit at 2024-04-20T12:04:28 (UTC). The position of the source is R.A. = 228.713 deg, DEC = 14.796 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The flare lasted for more than 100 seconds and reached a peak flux of ~1 x 10^-8 erg/s/cm^2 in the 0.5-4 keV band. Since only the basic data of the alert was transmitted to the ground, the information on the source property is limited. Further information may be provided once the full scientific telemetry data are received at the EP science center.\n \nNo previously known X-ray sources at a similar flux level are found within 3 arcmin around the source position.  \n \nThe above observation was made with the WXT instrument during the  commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36194.",
"published": "2024-04-20T14:23:07.974294Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-20T14:23:07.974307Z",
"modified": "2024-04-20T14:23:07.982894Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6784,
"topic": "gcn.circular",
"uuid": "96747bea-06c4-46c8-9a93-1270732d068a",
"title": "EP240420a: GWAC-F50A optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"data": {
"date": "24/04/21 07:47:22 GMT",
"from": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36206"
},
"title": "GCN CIRCULAR",
"number": "36206",
"subject": "EP240420a: GWAC-F50A optical upper limit"
},
"message_text": "L. P. Xin(NAOC), Y. G. Yang(HNU), C. WU(NAOC), Y. L. Qiu(NAOC), J. Wang(GXU/NAOC),\n\nH. L. Li(NAOC), C. Wu(NAOC), E. W. Liang(GXU), X. H. Han(NAOC), X. M. Lu(NAOC),\n\nR. S. Zhang(NAOC), Y. Xu(NAOC), Y.J . Xiao(NAOC), P. P. Zhang(NAOC), L. Lan(NAOC),\n\nJ. Y. Wei(NAOC) on behalf of the SVOM/GWAC team:\n\n\n\nWe began to observe X-ray transient EP240420a (Zhang et all., GCN 36194)\n\ndetected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission,\n\nwith GWAC-F50A telescope at Xinglong station, China, at 13:58:11 (UT), 20. April. 2024,\n\nabout 1.9 hours after the burst.\n\n\n\n\nThe weather was not good.\n\n\n\n\nAfter stacking 100*100s seconds, the candidate reported (An et al., GCN 23602)or\n\nany other new sources were not detected within the errorbox of EP-FXT (Han et al., GCN 23603)\n\nin our stacked image down to a limit magnitude of 19.5 mag\n\nin R band comparing to several nearby USNO B1.0 stars.\n\n\n\n\nWe acknowledge the excellent support from observation assistant Yangtong ZhengandWenlongDong.\n\n\n\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36206.",
"published": "2024-04-21T07:47:39.968418Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T07:47:39.968434Z",
"modified": "2024-04-21T07:47:39.976030Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6785,
"topic": "gcn.circular",
"uuid": "ecff41ff-24ba-4a4a-8761-fb4aa638dc63",
"title": "EP240420a: Nanshan optical counterpart observations",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/04/21 09:48:59 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36207"
},
"title": "GCN CIRCULAR",
"number": "36207",
"subject": "EP240420a: Nanshan optical counterpart observations"
},
"message_text": "U. Mahmut, A. Iskandar, J.Z. Liu, Y. Zhang (XAO), J. An, Z.P. Zhu, X. Liu, S.Q. Jiang, S.Y. Fu, D. Xu (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of the X-ray transient, EP 240420a, detected by EP/WXT (Zhang et al., GCN 36194) using the 1-m Nanshan Optical Wide-field Telescope (NOWT) and the Half-Meter-Telescope (HMT) located at Nanshan, Xinjiang, China.\n\nAt series of 300 s and 200 s NOWT frames in the V-band were obtained starting at 16:00:05 UT on 2024-04-20 and the median time is 4.58 hr after the EP trigger. An optical transient (OT) is marginally detected at the counterpart candidate position reported by NOT (An et al., GCN 36202) with V ~ 21.8 mag, calibrated with the PanSTAR field.\n\nAt HMT 40 x 60 frames without any filter were obtained and the median time is 4.32 hr after the EP trigger. No credible source is detected at the NOT position, down to a 3-sigma limiting magnitude of r ~ 20.0, calibrated with the PanSTAR field.\n\nThe NOT candidate is within the EP/FXT error circle (Han et al., GCN 36203). Comparison of the Nanshan observation with the NOT observation shows that the OT is decaying, being consistent with the behavior of GRB optical afterglows.\n\nWe therefore think the OT is the optical counterpart of EP 240420a, which could be a GRB.\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36207.",
"published": "2024-04-21T09:49:19.694084Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T09:49:19.694111Z",
"modified": "2024-04-21T09:49:19.702273Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6776,
"topic": "gcn.circular",
"uuid": "97f50a1f-3488-4ec7-96c8-7482784aebc7",
"title": "EP240420a: NOT optical counterpart candidate and potential host",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/04/21 05:16:55 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36202"
},
"title": "GCN CIRCULAR",
"number": "36202",
"subject": "EP240420a: NOT optical counterpart candidate and potential host"
},
"message_text": "J. An, Z.P. Zhu, X. Liu, S.Q. Jiang, S.Y. Fu, D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), P. Jonker (Radboud), M. A. Diaz Teodori (NOT) report on behalf of a large collaboration:\n\nWe observed the field of the X-ray transient, EP 240420a, detected by EP/WXT (Zhang et al., GCN 36194) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera, and obtained 5 x 200 s frames in the Sloan z-band with a median time of 2024-04-21T01:01:05.287, i.e., 0.54 day after the EP trigger.\n\nThe stacked z-band image has a 5-sigma limiting magnitude of z ~ 22.3. Within the 3 arcmin error circle of the EP/WXT, we identified an optical transient (OT) localized at\n\nR.A. = 15:14:55.08 (J2000)\nDec. = +14:48:17.8 (J2000)\n\nwith an uncertainty of radius ~ 0.3\" and z ~ 21.4 mag, calibrated with the PanSTARRS field.\n\nThe OT is ~ 1â south-west to a known source in the Legacy Survey (LS) which has r ~ 23.3 , z ~ 22.9, and a photometric redshift of z_phot ~ 0.82. This LS source could be the host of the OT.\n\nFurther observations are encouraged.\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36202.",
"published": "2024-04-21T05:17:09.930821Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T05:17:09.930834Z",
"modified": "2024-04-21T05:17:09.940785Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6792,
"topic": "gcn.circular",
"uuid": "b71a31f6-6616-4733-86b5-9d213eb2f129",
"title": "EP240420a: TNT upper limit to its optical counterpart",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/04/21 14:20:00 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36210"
},
"title": "GCN CIRCULAR",
"number": "36210",
"subject": "EP240420a: TNT upper limit to its optical counterpart"
},
"message_text": "J. Mo, X. F. Wang, H. W. Peng (THU), X. Li (BJP), Y. G. Sun, W. X. Li (NAOC) report the optical follow-up observations of EP240420a (Zhang et al., GCN 36194, Han et al., GCN 36203). These observations were conducted on 2024 April 20.75 UT in g and r bands, at ~4 hours after the EP-WXT detection, using the 80-cm Tsinghua-NAOC Telescope (TNT) located at Xinglong Observatory, Hebei Province, China. No optical counterpart candidates were detected.\nThe 3-sigma upper limits are reported as below:\ng ~ 21.6 mag\nr ~ 21.9 mag\nFurther followup observations are encouraged.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36210.",
"published": "2024-04-21T14:20:14.758755Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T14:20:14.758771Z",
"modified": "2024-04-21T14:20:14.766424Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6787,
"topic": "gcn.circular",
"uuid": "b5ea2b4f-4878-4e19-b0ca-9c940ed5d675",
"title": "EP 240420a: Xinglong decaying optical counterpart",
"submitter": "Hop gcn.circular",
"authors": "Dr Jie Zheng at Xinglong Observatory, National Astronomical Observatories ( NAOC), CAS <jiezheng@nao.cas.cn>",
"data": {
"date": "24/04/21 10:19:24 GMT",
"from": "Dr Jie Zheng at Xinglong Observatory, National Astronomical Observatories ( NAOC), CAS <jiezheng@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36209"
},
"title": "GCN CIRCULAR",
"number": "36209",
"subject": "EP 240420a: Xinglong decaying optical counterpart"
},
"message_text": "B. C. Wang, J. J. Jin, Z. Fan, H. Wu, M. He, H. Y. Mu, L. Ge, J. B. Zhang, J. Zheng, Y. Zhang, X. Li, Y. G. Sun, J. J. Jia, W. X. Li, S. J. Xue, H. Zou, X. N. Guan, D. Xu report on behalf of a large collaboration:\n\nWe observed the field of the X-ray transient, EP 240420a, detected by EP/WXT using the Xinglong 0.8-m telescope located at Xinglong, Hebei, China. We obtained 3 x 600 s clear-band frames with a median time of 2024-04-20T14:48:24, i.e., 2.7 hr after the EP trigger, we luckily found the optical counterpart of EP 240420a in the stacked image. The stacked clear-band image using a 0.8-m telescope has a 3-sigma limiting magnitude of ~ 21 mag, calibrated with the Pan-STARRS g band field. Inspection of the whole EP/WXT 3 arcmin error circle produces a few low S/N optical counterpart candidates. We detected no optical transient candidate during April 20T13:00-15:00 with the 60/90 cm Schmidt Telescope in Xinglong, Hebei, China. The upper limit is ï½19.5 m in the g-band. Then we performed clear-band photometry on the Xinglong 2.16-m telescope located at Xinglong, Hebei, China, and obtained 3x180s clear-band frames with a median time of 2024-04-20T20:20:30, i.e., 8.2 hr after the EP trigger. The stacked clear-band image using the 2.16-m telescope has a 5-sigma limiting magnitude of ~21.7 mag, calibrated with the Pan-STARRS g-band field. Inspection of the whole EP/WXT 3 arcmin error circle produces no optical counterpart candidates.\n\nWithin the 10 arcsec error circle of the EP/FXT, we identified an optical transient (OT) localized at\nR. A. = 15:14:55.072 , Dec. = 14:48:18.096 (J2000).\nThis OT has m = 20.657 +/- 0.4 (AB) in the Xinglong 0.8-m telescope image calibrated with the Pan-STARRS g band field.\n\nWe summarize our observation results as follows:\n\nObs. No. |     Start Time (UTC) | End Time (UTC) | Exposure Time (s) | Apparent mag (AB) | Telescope Name\n1 | 2024-04-20 13:00:00 | 2024-04-20 15:00:00 |  | > 19.5 | Xinglong Schmidt 60/90-cm Telescope\n2 | 2024-04-20 14:38:24 | 2024-04-20 14:58:20 | 3x600 s | 20.657 +/- 0.4 | Xinglong 0.8-m Telescope\n3 | 2024-04-20 20:17:20 | 2024-04-20 20:23:41 | 3x180 s | > 21.7 | Xinglong 2.16-m Telescope\n\nFurther observations are encouraged.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36209.",
"published": "2024-04-21T10:19:43.669312Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-21T10:19:43.669326Z",
"modified": "2024-04-21T10:19:43.678820Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6976,
"topic": "gcn.circular",
"uuid": "ce48be35-5ebe-4278-8f51-9d936ff762ba",
"title": "EP240426a: GMG optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "wangbaiting@ynao.ac.cn",
"data": {
"date": "24/04/26 14:10:11 GMT",
"from": "wangbaiting@ynao.ac.cn",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36315"
},
"title": "GCN CIRCULAR",
"number": "36315",
"subject": "EP240426a: GMG optical upper limit"
},
"message_text": "B.-T. Wang, R.-Z. Li, J. Mao, L.-Y. Zhu, Y.-Z. Cai, J.-M. Bai (YNAO) report:\n\nWe observed the field of EP-FXT detection of the candidate conterpart EP 2406026a (Sun et al. GCN 36313) by the GMG-2.4m telescope at the Lijiang station in Yunnan Observatories. The observation began at 2024-04-26T12:37:20. No optical counterpart was detected within the EP-FXT error circle.\n\nThe very preliminary upper limit can be given i>18.7.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36315.",
"published": "2024-04-26T14:10:28.689015Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-26T14:10:28.689034Z",
"modified": "2024-04-26T14:10:28.694639Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 6988,
"topic": "gcn.circular",
"uuid": "35f94d42-b4d3-4b2f-91a1-2a1bbba40a96",
"title": "EP240426a: YAHPT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>",
"data": {
"date": "24/04/26 16:57:35 GMT",
"from": "Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36323"
},
"title": "GCN CIRCULAR",
"number": "36323",
"subject": "EP240426a: YAHPT optical upper limit"
},
"message_text": "Tian-Rui Sun, Jin-Jun Geng, Jian Chen, Yan-Long Hua and Lei Hu report on behalf of the YAHPT team:\n\nFollowing the detection of EP240426a by Einstein Probe (Sun et al., GCN 36313),\nwe use the Yaoan High Precision Telescope at Yaoan Astronomy Observation Station (Yunnan province, China) to search and follow up.\n\nWe observed the target position in both Rc and Ic starting from 2024-04-26T12:47:25.100 with 300s exposure.\nWe did not detect any possible new optical counterpart with an uncertainty of 10 arcsec in the coadded image.\n\nUT (start) |5 sigma Upper Limit| Exposure Time | Filter\n2024-04-26T12:47:25.100| 21.26 | 300*8s | Rc\n2024-04-26T12:42:22.700| 21.12 | 300*8s | Ic\n\nThis non-detection result of the transient is in agreement with the previous circulars (Wang et al., 36315; Xiong et al.,36320).\nWe used the USNO B1.0 catalogue (R2mag and Imag) as the magnitude reference for calibration.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36323.",
"published": "2024-04-26T16:57:51.220617Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-26T16:57:51.220634Z",
"modified": "2024-04-26T16:57:51.224652Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7010,
"topic": "gcn.circular",
"uuid": "c677750d-96be-4ae9-ab30-909330ad5fec",
"title": "EP240426b: AST3-2 optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>",
"data": {
"date": "24/04/27 16:54:44 GMT",
"from": "Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36335"
},
"title": "GCN CIRCULAR",
"number": "36335",
"subject": "EP240426b: AST3-2 optical upper limit"
},
"message_text": "Tian-Rui Sun, Yan-Long Hua, Jin-Jun Geng, Xue-Feng Wu, Ke-Lai Meng (Purple Mountain Observatory, CAS), Xiao-Yan Li, Zheng-Yang Li, Yun Li, Xiang-Yan Yuan (Nanjing Institute of Astronomical Optics & Technology, CAS), Lifan Wang (TAMU), Xiao-Feng Wang, Mao-Kai Hu (Tsinghua University), Lei Hu (CMU) report on behalf the AST3 Team:\n\nFollowing the detection of EP240426b by Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) (Pan et al. GCN 36330),\nwe use Antarctic Survey Telescope 3-2 at Dome A, Antarctic (Latitude -80.4173, Longitude 77.0950) for follow-up.\nOur observation started on 2024-04-27T12:44:01.\nNo obvious optical source was detected with an uncertainty of 3 arcmin in radius.\nOur detection limit on the coadded images is down to 19.2 mag for total 36x60s with filter i.\nWe use the ATLASREFCAT2 (Tonry et al. 2018) as the magnitude calibration reference.\n\nWe thank Prof. Michael Ashley (UNSW) for his excellent support on the operation of AST3-2.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36335.",
"published": "2024-04-27T16:54:59.064511Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-27T16:54:59.064528Z",
"modified": "2024-04-27T16:54:59.071898Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7000,
"topic": "gcn.circular",
"uuid": "d6ba2060-7487-4d9f-a67c-df8428433e58",
"title": "EP240426b: EP-WXT detection of a new fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/04/27 05:01:10 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36330"
},
"title": "GCN CIRCULAR",
"number": "36330",
"subject": "EP240426b: EP-WXT detection of a new fast X-ray transient"
},
"message_text": "X. Pan, D. H. Zhao (NAOC, CAS), J. Q. Peng (IHEP, CAS), C. C. Jin, Z. X. Ling, Y. Liu, Z. X. Ling, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC,CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nWe report on the detection of a fast X-ray transient EP240426b at 2024-04-26T14:19:06 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The position of the source is R.A. = 173.787 deg, DEC = -40.741 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for ~300 seconds and has a peak flux of ~9.5 x 10^-10 erg/s/cm^2 in the 0.5-4 keV band. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.8(-0.3/+0.3) (with the column density fixed at the Galactic value of 8.08 x 10^20 cm^-2), giving an unabsorbed flux of 3.6(-0.6/+0.6) x 10^-10 erg/s/cm2 in the 0.5-4 keV band. The 1-sigma uncertainties are given for the above parameters.\n\nNote: EP240426b is about 40 degrees away from the 90% credible region of the recent BH-NS gravitational-wave event S240422ed (GCN 36236), therefore it is an independent source unrelated to this event.\n\nNo previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. Further multi-wavelength follow-up observations are encouraged to identify the nature of this X-ray flare.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36330.",
"published": "2024-04-27T05:01:28.532209Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-04-27T05:01:28.532227Z",
"modified": "2024-04-27T05:01:28.538443Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7253,
"topic": "gcn.circular",
"uuid": "87394188-406b-42c0-837b-5c6a60923c08",
"title": "EP240506a: Archival radio searching",
"submitter": "Hop gcn.circular",
"authors": "Ning Chang at Xinjiang Astronomical Observatory, CAS <changning@xao.ac.cn>",
"data": {
"date": "24/05/08 10:50:46 GMT",
"from": "Ning Chang at Xinjiang Astronomical Observatory, CAS <changning@xao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36414"
},
"title": "GCN CIRCULAR",
"number": "36414",
"subject": "EP240506a: Archival radio searching"
},
"message_text": "Ning Chang (XAO), Lang Cui (XAO), Yongfeng Huang (NJU), Tao An (SHAO), Jie Liao (XAO, UCAS), Pengfei Jiang (XAO), Wancheng Xu (XAO) and Dongyue Li(NAOC) report:\n\nWe report an archival radio source located within the error circle of the fast X-ray transient EP240506a. EP240506a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Li et al., GCN 36405). Aryan et al., (GCN 36408) observed the field of the EP240506a using the 40cm SLT, and only found a variable star which corresponds to SDSS J141557.82-164317.2 within the error circle of 3 arcmin. Perez-Garcia et al. (GCN 36412) reported that no source was detected within the error position of the field of EP240506a using the telescopes of the Global BOOTES Network. Additionally, Tinyanont et al. (GCN 36413) observed the field of EP240506a using the 0.7-m telescope of TRT and found no uncatalogued optical transient.\n\nWe have searched for a radio counterpart using the data from the Rapid ASKAP Continuum Survey (RACS, Hale et al. 2021 PASA 38, e058). We only found one radio detection in the RACS images within the uncertainty of 3 arcmin reported in GCN 36405. We also inspected the VLA Sky Survey data (VLASS, Gordon et al. 2021 ApJS 255, 30) but found no detections.\n\nThe fluxes and position of this radio source from RACS are:\n2019-04-27: 2.74 mJy (0.8875 GHz, from RACS low, with RA\u0014h15m56.348s, DEC=-16d41m22.947s)\n2021-02-12: 2.46 mJy (1.3675 GHz, from RACS mid, with RA\u0014h15m56.187s, DEC=-16d41m22.673s)\n2022-01-09: 1.42 mJy (1.655 GHz, from RACS high, with RA\u0014h15m56.12s, DEC=-16d41m23.16s)\n\nThe power-law spectral index is -1.47. This radio source is about 1.6 arcmin away from the X-ray transient EP240506a position, and about 2 arcmin away from the variable star position. We further inspected the AllWISE Source Catalog and found that WISEA J141556.28-164124.4 is close to the radio source about 2 arcsec away. We infer that the radio source could be a background galaxy.\n\nThe figures of this radio source can be accessed from https://drive.google.com/drive/folders/1Yy9nHYF9JKhmnQhD27fqg5vQkaBpl4Nr?usp=sharing\n\nMulti-wavelength follow-up observations are strongly encouraged to help further reveal the nature of the new X-ray transient.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36414.",
"published": "2024-05-08T10:51:07.949713Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-08T10:51:07.949735Z",
"modified": "2024-05-08T10:51:07.956988Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7245,
"topic": "gcn.circular",
"uuid": "c6c60a73-5f39-4bf2-9b5b-c46ec4465da2",
"title": "EP240506a: BOOTES Network optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"data": {
"date": "24/05/08 06:12:28 GMT",
"from": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36412"
},
"title": "GCN CIRCULAR",
"number": "36412",
"subject": "EP240506a: BOOTES Network optical upper limit"
},
"message_text": "I. Perez-Garcia, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, S.-Y. Wu and A. J. Castro-Tirado (IAA-CSIC, Granada), Y.-D. Hu (INAF-OAB), D. Hiriart, W. H. Lee (UNAM), I. M. Carrasco-Garcia (SMA), I. H. Park (SKKU), L. Hernandez-Garcia (Univ. de Valparaiso), C. Perez del Pulgar, A. Castellon, A. Reina (Univ. de Malaga), B.-B. Zhang (Nanjing Univ.), A. Maury (Space, San Pedro de Atacama), D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, and X. H. Zhao (Yunnan Observatories of CAS), on behalf of a larger collaboration, report:\n\nFollowing the detection of EP240506a by EP-WXT (Li et al., GCNC 36405), several telescopes of the Global BOOTES Network pointed to its position on the sky.\n\nThe BOOTES-5/JGT 0.6m robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) observed the fast X-ray transient location on May. 7, 07:02 UT (1.08 days after trigger). In the co-added frame (60 x 59 s, clear filter), no source is detected within the error position down to 20.6 mag.\n\nThe BOOTES-7 0.6m robotic telescope at San Pedro de Atacama (Chile) also observed the transient position on May, 7 at 07:12 UT (1.09 days after trigger). In the co-added image (60 x 32 s, clear filter), no optical counterpart is detected down to 20.3 mag.\n\nLater on, we also triggered the BOOTES-4/MET 0.6m robotic telescope at Lijiang Astronomical Observatory (China), also resulting on a non-detection. All the above-mentioned upper limits are in agreement with other reports (cf. Aryan et al., GCCN 36408).\n\nWe thank the staff at the BOOTES sites for their excellent support.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36412.",
"published": "2024-05-08T06:12:46.921392Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-08T06:12:46.921409Z",
"modified": "2024-05-08T06:12:46.930036Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7258,
"topic": "gcn.circular",
"uuid": "b7a1a276-802d-4bad-bc95-d2e12e1958b6",
"title": "EP240506a: CrAO ZTSH optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"data": {
"date": "24/05/08 18:48:21 GMT",
"from": "Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36417"
},
"title": "GCN CIRCULAR",
"number": "36417",
"subject": "EP240506a: CrAO ZTSH optical upper limit"
},
"message_text": "EP240506a: CrAO ZTSH optical upper limit\n\nN. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), S. Belkin (IKI) report on behalf of GRB-IKI-FuN collaboration:\n\nWe observed the EP240506a detected by EP-WXT (GCN 36405) with 2.6-meter ZTSh telescope of CrAO, equipped with CCD-photometer and the R-filter. The observations started on 2024-05-07 at 20:43 (UT), i.e. ~1.6 day after EP trigger. The series of 31x120s images were taken.\nWe do not detect any optical object within EP-WXT localization area. The preliminary photometry is following:\n\nDate UT start MJD Exp. Filter OT Err. UL(3sigma)\n (mid, days) (s)\n\n2024-05-07 20:58:29 60437.88266 28x120 R n/d n/d 22.5\n\nThe result is in agreement with previous observations (Aryan et al., GCN 36408; Perez-Garcia et al., GCN 36412; Tinyanont et al., GCN 36413).\nWe also do not detect any optical source consistent with the location of WISEA J141556.28-164124.4 reported by Chang et al. (GCN 36414).\nThe variable star SDSS J141557.82-164317.2 mentioned in (Chang et al., GCN 36414) does not show any variability in comparison with USNO-B1.0 (R2\u0017.02) for which we measure the magnitude of R\u0016.92 +/- 0.10.\n\nThe magnitudes were calibrated using nearby USNO-B1.0 stars (R2 magnitude). No correction has been made for a Galactic extinction towards the EP240506a.\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36417.",
"published": "2024-05-08T18:48:44.151783Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-08T18:48:44.151804Z",
"modified": "2024-05-08T18:48:44.158033Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7232,
"topic": "gcn.circular",
"uuid": "3b53cb30-a731-4e81-8d73-ffedf5d06b40",
"title": "EP240506a: EP-WXT detection of a new fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/05/07 07:01:44 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36405"
},
"title": "GCN CIRCULAR",
"number": "36405",
"subject": "EP240506a: EP-WXT detection of a new fast X-ray transient"
},
"message_text": "D.Y. Li (NAOC, CAS), J. Yang (NJU), A. Li (BNU), W. Yuan, Z. X. Ling, Y. Liu, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC,CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nWe report on the detection of a fast X-ray transient, designated EP240506a, at 2024-05-06T05:01:39 (UTC) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The position of the source is R.A. = 213.978 deg, DEC = -16.715 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for about 50 seconds and has a peak flux of 1 x 10^-8 erg/s/cm^2 in the 0.5-4 keV band. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.0(+/- 0.5) (with the column density fixed at the Galactic value of 9.0 x 10^20 cm^-2), giving an unabsorbed flux of 1.1(+0.3, -0.2) x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The 1-sigma uncertainties are given for the above parameters.\n\nNo previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. Further multi-wavelength follow-up observations are encouraged to identify the nature of this X-ray flare.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36405.",
"published": "2024-05-07T07:02:02.190555Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-07T07:02:02.190573Z",
"modified": "2024-05-07T07:02:02.212256Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7239,
"topic": "gcn.circular",
"uuid": "9ee9eda8-3dc2-44c9-b316-28a76d20bb3a",
"title": "EP240506a: Optical upper limit with Kinder observations",
"submitter": "Hop gcn.circular",
"authors": "Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>",
"data": {
"date": "24/05/07 17:19:29 GMT",
"from": "Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36408"
},
"title": "GCN CIRCULAR",
"number": "36408",
"subject": "EP240506a: Optical upper limit with Kinder observations"
},
"message_text": "A. Aryan (NCUIA), S. Yang (HNAS), T.-W. Chen, C.-S. Lin, C.-C. Ngeow, W.-J. Hou, H.-Y. Hsiao, C.-H. Lai, A. Sankar.K, M.-H. Lee, Y.-C. Pan, H.-C. Lin, J.-K. Guo (all NCUIA), H. F. Stevance, S. J. Smartt (Oxford/QUB), S. Srivastav, J. Gillanders (Oxford), M. Fulton, T. Moore, C. Angus, and A. Aamer (all QUB) report:\n\nWe observed the field of the fast X-ray transient EP240506a (Li et al., GCN 36405) using the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen et al., AstroNote 2021-92). The first SLT epoch of observations started at 13:07 UT on 07th of May 2024 (MJD = 60437.547), 1.34 days after the EP trigger. We used the Kinder pipeline (Yang et al. A&A 646, A22) to stack the images and subtract the stacked images with the Legacy Survey DR10 template images.\n\nWe detect the presence of a variable star in the subtracted image at R.A. = 14:15:57.85 and DEC = -16:43:17.30, which corresponds to SDSS J141557.82-164317.2 with an r-band magnitude of 17.52 mag.\n\nBesides this, we do not detect any optical counterpart in the errorbox of 3 arcminute around the position of the EP source specified by Li et al., (GCN 36405). The details of the observations and the corresponding 2.5 sigma upper limit (in the AB system) in our combined image are as follows:\n\nTelescope | Filter | MJD (start) | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass\nSLT | r | 60437.547 | 1.34 days | 300 sec * 29 | > 21.82 | 2\".2 | 1.35\n\nThe reported upper limit is calibrated against nearby stars from SDSS and is not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.09 mag in the direction of the EP source (Schlafly & Finkbeiner 2011).\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36408.",
"published": "2024-05-07T17:20:29.876836Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-07T17:20:29.876850Z",
"modified": "2024-05-07T17:20:29.884940Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7252,
"topic": "gcn.circular",
"uuid": "46ac40bd-42c7-45a6-b36b-8a7d167d5f67",
"title": "EP240506a: TRT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"data": {
"date": "24/05/08 10:19:12 GMT",
"from": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36413"
},
"title": "GCN CIRCULAR",
"number": "36413",
"subject": "EP240506a: TRT optical upper limit"
},
"message_text": "S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Q. Jiang, Z.P. Zhu, X. Liu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of EP240506a (Li et al., GCN 36405) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Springbrook Observatory, New South Wales, Australia. Observations started at 09:53:36.57 UT on 2024-05-07, i.e., 1.20 day after the EP trigger, and 6 x 300 s R-band and 6 x 300 s I-band frames were obtained, respectively.\n\nNo uncatalogued optical transient is detected in the stacked R-band and I-band images within the 3 arcmin EP/WXT error circle (Li et al., GCN 36405), down to 3-sigma limiting magnitudes of R ~ 21.6 and I ~ 21.0, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36413.",
"published": "2024-05-08T10:19:40.815621Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-08T10:19:40.815638Z",
"modified": "2024-05-08T10:19:40.826696Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7260,
"topic": "gcn.circular",
"uuid": "7966bc86-8737-467a-aa51-35b24d8afb78",
"title": "EP240506a: Xinglong optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Dr Jie Zheng at Xinglong Observatory, National Astronomical Observatories ( NAOC), CAS <jiezheng@nao.cas.cn>",
"data": {
"date": "24/05/09 02:55:13 GMT",
"from": "Dr Jie Zheng at Xinglong Observatory, National Astronomical Observatories ( NAOC), CAS <jiezheng@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36419"
},
"title": "GCN CIRCULAR",
"number": "36419",
"subject": "EP240506a: Xinglong optical upper limit"
},
"message_text": "J.-J. Jin(NAOC), H.-Y. Mu(NAOC), Z. Fan(NAOC), H. Wu(NAOC), J. Zheng(NAOC), S. Liu(NAOC) report on behalf of a large collaboration:\n\nFollowing the detection of EP240506a by EP-WXT (Li et al., GCN 36405), we observed the field of EP240506a using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x600s clear-band frames with a median time of 2024-05-07T15:16:34 i.e., 10 hr after the EP trigger.\n\nNo uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (Li et al., GCN 36405), down to 3-sigma limiting magnitudes of g ~ 23.1, calibrated with Pan-STARRS sources in the field. Also, there is no apparent brightening for the cataloged sources within the error circle.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36419.",
"published": "2024-05-09T02:55:30.549146Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-09T02:55:30.549160Z",
"modified": "2024-05-09T02:55:30.557149Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7461,
"topic": "gcn.circular",
"uuid": "27227942-21f1-4b61-89ea-af675444b311",
"title": "EP240518a: EP-WXT detection of a new X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/05/18 15:01:23 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36512"
},
"title": "GCN CIRCULAR",
"number": "36512",
"subject": "EP240518a: EP-WXT detection of a new X-ray transient"
},
"message_text": "Q.Y. Wu (NAOC, CAS), A. Li (BNU), Y. Liu, W. Yuan, Z. X. Ling, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC,CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nWe report on the detection of a new X-ray transient, designated EP240518a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission during a calibration observation. The transient triggered the WXT on-board processing unit at 2024-05-18T13:01:50 (UTC). The position of the source is R.A. = 216.955 deg, DEC = -49.565 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for more than 1000 seconds and has an average flux of 8 x 10^-11 erg/s/cm^2 in the 0.5-4 keV band.\n\nNo previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. More information will be provided once the data has been transmitted through a ground station. Further multi-wavelength follow-up observations are encouraged to identify the nature of this X-ray flare.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36512.",
"published": "2024-05-18T15:01:38.744359Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-18T15:01:38.744378Z",
"modified": "2024-05-18T15:01:38.751800Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7528,
"topic": "gcn.circular",
"uuid": "aafea27d-13b9-46fc-94f1-1bce15952ca1",
"title": "EP240518a: GSP optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/05/22 09:08:13 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36529"
},
"title": "GCN CIRCULAR",
"number": "36529",
"subject": "EP240518a: GSP optical upper limit"
},
"message_text": "W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report:\nFollowing the detection of the fast X-ray transient EP240518a by the Einstein Probe (Wu et al., GCN 36512; Wu et al., GCN 36514), we initiated observations of the transient's location in the r band on May 18 at 16:46 UT, ~4 hours after the trigger. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at Siding Spring Observatory in Australia.\n\nWe report that no new optical source was detected in the co-added images within the EP/FXT error box down to a limiting magnitude of ~21.5. The possible M-type dwarf star named Gaia DR3 5899529595616014848, mentioned in Wu et al. (GCN 36514), was detected without significant variation compared to archival DECam images.\n\nThese observations were taken as part of the Global Supernova Project.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36529.",
"published": "2024-05-22T09:08:23.703629Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-22T09:08:23.703649Z",
"modified": "2024-05-22T09:08:23.715634Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 7471,
"topic": "gcn.circular",
"uuid": "a40ff576-f5d5-451a-86cf-3343656bd201",
"title": "EP240518a: possibly identified with a flare star by EP-FXT",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/05/19 16:22:25 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36514"
},
"title": "GCN CIRCULAR",
"number": "36514",
"subject": "EP240518a: possibly identified with a flare star by EP-FXT"
},
"message_text": "Q.Y. Wu (NAOC, CAS), A. Li (BNU), Y. Liu, W. Yuan, Z. X. Ling, C. Zhang, C. C. Jin, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang (NAOC,CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nFollowing the detection of the X-ray transient EP240518a (Wu et al., GCN 36512) by the Wide-field X-ray Telescope (WXT) of Einstein Probe (EP), we performed an observation with the Follow-up X-ray Telescope (FXT) on board EP. The observation started at 2024-05-18T15:46:11, about 3 hours after the WXT detection, with a net exposure time of 6.0 ks.\n\nWithin the error circle of EP240518a, an X-ray source was clearly detected at R.A. = 216.954 deg, DEC = -49.584 deg, with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic). It is 7.9 arcsec away from a known X-ray source 1eRASS J142749.6-493505 with an archived flux of 6.0 x 10^-14 erg/s/cm^2 in 0.2-2.3 keV. The absorbed flux of the FXT source is 1.1(+0.3/-0.2) x 10^-13 erg/s/cm^2 (90% C.L.) in 0.5-10 keV, which is generally consistent with the eRASS flux but is about 3 orders of magnitude lower than the peak flux of EP240518a (~8 x 10^-11 erg/s/cm^2). This suggests that the time scale of EP240518a, if associated with the FXT source, is shorter than several hours. The FXT spectrum can be well fitted with the tbabs*apec model with the plasma temperature kT = 0.21(+0.10/-0.06) keV (90% C.L.). A possible M-type dwarf star named Gaia DR3 5899529595616014848, with a distance of about 35 pc, is located around 7 arcsec from the FXT position. If the FXT source is related to the eRASS source and the dwarf, then EP240518a may be a stellar flare with a luminosity of 1.3 x 10^31 erg/s in 0.5-4.0 keV.\n\nPlease note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36514.",
"published": "2024-05-19T16:22:41.752921Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-05-19T16:22:41.752936Z",
"modified": "2024-05-19T16:22:41.761516Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 49646,
"topic": "gcn.circular",
"uuid": "500e350f-4aaa-421f-a851-d8275045ed95",
"title": "EP240617a: BOOTES-6/DPRT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"data": {
"date": "24/06/18 21:56:11 GMT",
"from": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36693"
},
"title": "GCN CIRCULAR",
"number": "36693",
"subject": "EP240617a: BOOTES-6/DPRT optical upper limit"
},
"message_text": "I. Perez-Garcia, E. Fernandez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, S.-Y. Wu and A. J. Castro-Tirado (IAA-CSIC, Granada), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report:\n\nFollowing the detection of the fast X-ray transient EP240617a (a likely GRB) by the Einstein Probe (Zhou et al. GCNC 36691, Yang et al. GCNC 36692), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) observed the fast X-ray transient location starting on June 18, 19:59 UT (~ 31.6 h after trigger) in different optical bands. No new optical source is detected on the co-added images (clear-filter) within the EP/WXT error box down to 20.4 mag.\n\nWe thank the staff at Boyden Observatory for their excellent support.\n\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36693.",
"published": "2024-06-18T21:56:22.563001Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-18T21:56:22.563020Z",
"modified": "2024-06-18T21:56:22.566745Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 49492,
"topic": "gcn.circular",
"uuid": "b55b25b9-8b15-47c1-98b8-e900e8a35cb6",
"title": "EP240617a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/18 13:30:06 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36691"
},
"title": "GCN CIRCULAR",
"number": "36691",
"subject": "EP240617a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "H. Zhou (PMO, CAS), W. Chen, H. Sun, W. D. Zhang, J. W. Hu, D. Y. Li, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Yang, C. Y. Dai (NJU) Y. F. Liang (PMO), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n \nWe report on the detection of a fast X-ray transient, designated EP240617a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2024-06-17T12:19:13 (UTC). The position of the source is R.A. = 285.030 deg, DEC = -22.561 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for over 300 seconds before the observation was interrupted due to earth occultation. The lightcurve of the transient exhibits a multi-peak profile. The peak unabsorbed flux is around 1.4(+/-0.1) x 10^-8 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.1(+/-0.1) (with the column density fixed at the Galactic value of 1.7 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 3.5(+/-0.3) x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.\n\nNo previously known bright X-ray sources are found within the error circle around the source position. Further follow-up observations are encouraged to identify the nature of this X-ray transient. \n\nThe above observations were made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36691.",
"published": "2024-06-18T13:30:18.702786Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-18T13:30:18.702806Z",
"modified": "2024-06-18T13:30:18.706560Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 49561,
"topic": "gcn.circular",
"uuid": "1eb7df4f-17f8-45cb-9b12-925f7e215eaa",
"title": "EP240617a is likely a GRB event",
"submitter": "Hop gcn.circular",
"authors": "jyang@smail.nju.edu.cn",
"data": {
"date": "24/06/18 15:51:31 GMT",
"from": "jyang@smail.nju.edu.cn",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36692"
},
"title": "GCN CIRCULAR",
"number": "36692",
"subject": "EP240617a is likely a GRB event"
},
"message_text": "Jun Yang (NJU), Yi-Han Iris Yin (NJU), Binbin Zhang (NJU), Hui Sun (NAOC), Qinyu Wu (NAOC) and Xuefeng Wu (PMO) report on behalf of large collaboration:\n\nOur team has followed up on EP's X-ray flare detection at 2024-06-17T12:19:13 UTC (EP240617a; GCN Circular 36691) and discovered a weak, untriggered gamma-ray transient in the Fermi/GBM data within the occurrence time interval of EP240617a. This transient lasted approximately 100 seconds and its location aligns with that of EP240617a.\n\nConsidering the factors that the gamma-ray transient is consistent with EP240617a in terms of event time and location, we are inclined to claim that this is likely a GRB event. A preliminary spectral analysis indicates that its peak energy is below one hundred keV, which suggests its classification as an X-ray rich GRB.\n\nWe strongly recommend further follow-up on EP240617a to confirm its physical nature and to detect any afterglows.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36692.",
"published": "2024-06-18T15:51:47.953693Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-18T15:51:47.953715Z",
"modified": "2024-06-18T15:51:47.962452Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 52031,
"topic": "gcn.circular",
"uuid": "15c09c48-a610-491f-b2cc-93be468f31dd",
"title": "EP240617a: STEP/T80S optical limits",
"submitter": "Hop gcn.circular",
"authors": "André Santos at Centro Brasileiro de Pesquisas FÃsicas (CBPF) <andsouzasanttos@gmail.com>",
"data": {
"date": "24/06/19 23:42:54 GMT",
"from": "André Santos at Centro Brasileiro de Pesquisas FÃsicas (CBPF) <andsouzasanttos@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36707"
},
"title": "GCN CIRCULAR",
"number": "36707",
"subject": "EP240617a: STEP/T80S optical limits"
},
"message_text": "A. Santos (CBPF), C. R. Bom (CBPF), C. D. Kilpatrick (Northwestern), L. Santana-Silva (CBPF), P. Darc (CBPF), C. Mendes de Oliveira (IAG-USP) report on behalf of the STEP collaboration:\n\n\nWe conducted optical follow up of the fast X-ray transient EP240617a by the Einstein Probe (GCN [36691](https://gcn.nasa.gov/circulars/36691), [36692](https://gcn.nasa.gov/circulars/36691)) with the T80S 0.8-m robotic telescope using the 1.4 x 1.4 field-of-view T80S-Cam imager (see Santos et al., 2024, MNRAS, 529, 59 for details). The observations started on June 19, 05:10 UT (~41 hours after the trigger). We obtained 360s (3x120s) images in both i and z bands with the T80S camera centered at R.A.=19:00:07.29 and Decl.=-22:33:39.60 (J2000). Subtracting Pan-STARRS 3pi template images from the T80S frames using photpipe (Rest et al., 2005), we do not detect any sources in our difference images and derive 3-sigma limiting magnitudes of z > 20.6 and i > 20.9 mag for any optical transient.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36707.",
"published": "2024-06-19T23:43:05.127485Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-19T23:43:05.127515Z",
"modified": "2024-06-19T23:43:05.132391Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 55148,
"topic": "gcn.circular",
"uuid": "6e9ee7eb-6aef-420b-8185-00a6c9157773",
"title": "EP240617a: tentative Swift/XRT detection of the afterglow",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/21 09:36:34 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36722"
},
"title": "GCN CIRCULAR",
"number": "36722",
"subject": "EP240617a: tentative Swift/XRT detection of the afterglow"
},
"message_text": "H. Sun, W. Chen (NAOC, CAS), H. Zhou (PMO, CAS), W. D. Zhang, D. Y. Li, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240617a by the Einstein Probe (Zhou et al., GCN 36691), which is likely a gamma-ray burst based on Fermi/GBM data (Yang et al., GCN 36692), we triggered a Swift target of opportunity observation (ObsID: 00016669001). The XRT onboard Swift began the observation at 2024-06-20T17:57:41 UTC, about 77 hours after the WXT detection, with an exposure time of 1.69 ks in the Photon Counting mode.\n\nWithin the 3 arcmin error radius of the WXT position, we have tentatively detected a weak signal with a significance of 5.3 sigma (as evaluated by the Li-Ma formula, Li & Ma 1983, ApJ, 272, 317) at R.A.\u0019:00:06.0, DEC=-22:33:29.9 (J2000) with an uncertainty of 7.5 arcsec (radius, 90% C.L. statistical and systematic). The position of the source is 0.3 arcmin away from the WXT detection and is thus spatially consistent with EP240617a, suggesting that we detected the X-ray afterglow. The source has an average count rate of 5.1 x 10^-3 cps. Assuming an absorbed power-law model with a Galactic column density of 1.7 x 10^21 cm^-2 and a photon index of 2, the estimated flux in 0.3-10 keV is 1.9 x 10^-13 ergs/cm^2/s.\n\nFurther follow-up observations are encouraged to search for the multi-band afterglows.\n\nWe thank the Neil Gehrels Swift Observatory team for making the X-ray observation possible.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36722.",
"published": "2024-06-21T09:36:45.238345Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-21T09:36:45.238363Z",
"modified": "2024-06-21T09:36:45.248272Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 53651,
"topic": "gcn.circular",
"uuid": "0de153dc-4ca8-473f-b984-43262f0de7ed",
"title": "EP240618a: Abastumani optical observationsEP240618a",
"submitter": "Hop gcn.circular",
"authors": "XXXX at IKI <alex@cgrsmx.iki.rssi.ru>",
"data": {
"date": "24/06/20 17:11:44 GMT",
"from": "XXXX at IKI <alex@cgrsmx.iki.rssi.ru>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36714"
},
"title": "GCN CIRCULAR",
"number": "36714",
"subject": "EP240618a: Abastumani optical observationsEP240618a"
},
"message_text": "N. Pankov (HSE, IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO) report on behalf of GRB-IKI-FuN collaboration:\n\nWe observed the refined error circle of EP240618a (Sun et al., GCN 36690) with AS-32 telescope of Abastumani Observatory (AbAO) equipped with CCD photometer and the R-filter to search for an optical counterpart. The observations were taken on dates 2024-06-18 and 2024-06-19. The first series is consist of 66x60 sec images, while latter one is 120x60 sec. Using image differencing, we find no new source within the localization circle or any brightness excess of catalog sources. The obtained results are consistent with observations by other telescopes (Wu et al., GCN 36701; Adami et al., GCN 36702; Tinyanont et al., GCN 36710; Akl et al., GCN 36712). Preliminary upper limits are following:\n\nDate UT start t-T0 Exp. Filter OT Err. UL(3 sigma)\n (mid, days) (s)\n2024-06-18 18:18:51 0.524398 64x60 R n/d n/d 19.6\n2024-06-19 21:45:02 1.667581 120x60 R n/d n/d 20.1\n\nThe difference image has an upper limit of 19.9 mag. The magnitudes were calibrated using nearby stars from USNO-B1.0 (R2 magnitude) catalog. The magnitudes are not corrected for the Galactic extinction towards EP240618a, which is A(V) = 0.4294 mag (S&F 2011).\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36714.",
"published": "2024-06-20T17:11:58.356768Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-20T17:11:58.356788Z",
"modified": "2024-06-20T17:11:58.365755Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 51330,
"topic": "gcn.circular",
"uuid": "b836213f-f910-426a-a257-36cf6f1741ef",
"title": "EP240618a: BOOTES-6/DPRT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"data": {
"date": "24/06/19 15:31:34 GMT",
"from": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36701"
},
"title": "GCN CIRCULAR",
"number": "36701",
"subject": "EP240618a: BOOTES-6/DPRT optical upper limit"
},
"message_text": "S.-Y. Wu, I. Perez-Garcia, E. Fernandez-Garcia, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report:\n\nFollowing the detection of the fast X-ray transient EP240618a by the Einstein Probe (Sun et al. GCNC 36690), the BOOTES-6/DPRT 0.6m robotic telescope at Boyden Observatory in Maselspoort (South Africa) observed the fast X-ray transient location starting on June 18, 20:52 UT (~ 15.1 h after trigger) in different optical bands. No new optical source is detected on the co-added images (clear-filter) within the EP/FXT 30â radius error box down to 20.2 mag.\n\nWe thank the staff at Boyden Observatory for their excellent support.\n\n\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36701.",
"published": "2024-06-19T15:31:45.126464Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-19T15:31:45.126484Z",
"modified": "2024-06-19T15:31:45.131867Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 49389,
"topic": "gcn.circular",
"uuid": "e8439864-d9f6-41d5-b52d-93ecd6e7a7f9",
"title": "EP240618a: EP-WXT detection of a fast X-ray transient and EP-FXT quick follow-up",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/18 12:34:18 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36690"
},
"title": "GCN CIRCULAR",
"number": "36690",
"subject": "EP240618a: EP-WXT detection of a fast X-ray transient and EP-FXT quick follow-up"
},
"message_text": "H. Sun, W. Chen (NAOC, CAS), H. Zhou (PMO, CAS), W. D. Zhang, J. W. Hu, D. Y. Li, Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Yang, C. Y. Dai (NJU) Y. F. Liang (PMO), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n\n\nWe report on the detection of a fast X-ray transient, designated EP240618a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient triggered the WXT on-board processing unit at 2024-06-18T05:43:43 (UTC). The position of the source is R.A. = 281.627 deg, DEC = 23.820 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for approximately 100 seconds and has a peak unabsorbed flux of ~1.5 x 10^-8 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.2(+/-0.4) (with the column density fixed at the Galactic value of 1.98 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 2.9(+0.7/-0.6) x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. \n\nFollowing the WXT detection, we performed a follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP, which started at 2024-06-18T06:55:00 (UTC), about 1 hour after the WXT detection. An X-ray source was clearly detected at R.A. = 281.648 deg, DEC = 23.833 deg (R.A. = 18:46:35.4, Dec = 23:49:57.0; J2000), with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic), which is 1.4 arcmin away from the WXT position of EP240618a. The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 1.98 x 10^21 cm^-2 and a photon index of 2.0(+/-0.1). The derived unabsorbed flux in 0.5-10 keV is 3.0(+/-0.3) x 10^-12 erg/s/cm2. During the observation, the flux of the source was decaying with time. Considering this source being within the error circle of the WXT transient, we suggest it being the late-time X-ray emission from EP240618a.\n\nFurther follow-up observations are encouraged to identify the nature of this X-ray transient. \n\nThe above observations were made with the WXT and FXT instruments during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36690.",
"published": "2024-06-18T12:34:29.489017Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-18T12:34:29.489035Z",
"modified": "2024-06-18T12:34:29.493755Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 53025,
"topic": "gcn.circular",
"uuid": "8e4f2569-63fe-41e6-95e7-d5d5a213367a",
"title": "EP240618a: GRANDMA Optical Upper Limits",
"submitter": "Hop gcn.circular",
"authors": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"data": {
"date": "24/06/20 09:24:27 GMT",
"from": "Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36712"
},
"title": "GCN CIRCULAR",
"number": "36712",
"subject": "EP240618a: GRANDMA Optical Upper Limits"
},
"message_text": "D. Akl (AUS), M. Masek (FZU), C. Andrade (UMN), E. G. Elhosseiny (NRIAG), H. Peng (THU), L. Wang (XAO), S. Antier (OCA), S. Karpov (FZU), M. Coughlin (UMN), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), D. Turpin (CEA-Saclay/Irfu), N. Guessoum (AUS), T. Pradier (Unistra/IPHC), J.-G. Ducoin (CPPM), M. Prouza (FZU), A. Klotz (CNRS-OMP-IRAP), M. Boer, A. S. Gervasoni, C. Limonta (OCA), Y.Rajabov, O.Burkhonov (UBAI), Y.Tillayev, S.Ehgamberdiev (UBAI, NUUz), T.Sadibekova (UBAI-CEA), M. Freeberg (KNC), M. Serrau (KNC), M. Odeh (AKO), C. Galdies (KNC), A. LeCalloch (Berkeley), N. Leroy (IJCLAB) on behalf of the GRANDMA collaboration:\n\nWe performed observations with GRANDMA and its citizen science project Kilonova-catcher (KNC) on the X-ray transient EP240618a detected by Einstein Probe (EP) WXT on T0 = 2024-06-18T05:43:43 (GCN 36690). We monitored the source with 8 telescopes, including TAROT-TCH, TAROT-TCA, FRAM-CTA-N, and UBAI-NT60, from 2024-06-18T16:10:05 to 2024-06-19T09-57-01 UTC, starting 0.43 days after the EP trigger.\n\nWe did not find any new optical counterpart in any of our frames within 30 arcsec radius centered around Ra/Dec: 281.648/ 23.833 deg, consistent with the reports from (Tinyanont et al., GCN 36710; Adami et al., GCN 36702; Wu et al., GCN 36701).\n\nAll our observations and upper limits, which correspond to the depth of the full image (given in the AB system), can be found here:\nhttps://skyportal-icare.ijclab.in2p3.fr/public/sources/EP240618a/version/8f2a92bbe70faf40c582c7454103e505\n\nBelow is the version that can be downloaded from the link above:\n+--------------+----------+----------------+-------------------+\n| MJD | Filter | Lim.Mag | Instrument |\n+==============+==========+================+===================+\n| 60479.687743 | I | 18.96 | UBAI/NT-60 |\n+--------------+----------+----------------+-------------------+\n| 60479.942361 | sdssg | 17.82 | TAROT/TCA |\n+--------------+----------+----------------+-------------------+\n| 60479.942361 | sdssg | 17.83 | TAROT/TCH |\n+--------------+----------+----------------+-------------------+\n| 60479.912306 | R | 17.97 | FRAM-CTA-N |\n+--------------+----------+----------------+-------------------+\n| 60480.406678 | R | 19.29 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60479.993831 | V | 20.26 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60479.759005 | I | 19.54 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60479.683044 | R | 19.54 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60480.027174 | sdssg | 20.15 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60479.983422 | sdssr | 19.93 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60479.664595 | V | 19.65 | KNC |\n+--------------+----------+----------------+-------------------+\n| 60479.949853 | G | 20.40 | KNC |\n+--------------+----------+----------------+-------------------+\n\nWe note that in the Skyportal page above, bessellv, bessellr, and besselli filters correspond to V, R, and I Johnson Cousin filters, respectively.\nGeneric telescopes in the Skyportal page correspond to KNC telescopes.\n\nAll the data have been reduced by a single data processing pipeline STDPIPE (Karpov et al., 2022).\n\nImages obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog while images taken with Sloan filters were calibrated using the Pan-STARRS DR1 Catalog.\nWe note that some amateur telescopes use green filters, which were calibrated with the Gaia catalog.\n\nWe use the Skyportal application (skyportal.io) to monitor our observational campaign.\n\nWe thank the Einstein Probe team for useful communication.\n\nGRANDMA is a worldwide telescope network (https://grandma.lal.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/).\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36712.",
"published": "2024-06-20T09:24:38.214806Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-20T09:24:38.214825Z",
"modified": "2024-06-20T09:24:38.219622Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 57418,
"topic": "gcn.circular",
"uuid": "0c128f57-a86d-4756-978b-2e4150ef66f1",
"title": "EP240618a: GSP optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/06/22 09:48:46 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36731"
},
"title": "GCN CIRCULAR",
"number": "36731",
"subject": "EP240618a: GSP optical upper limit"
},
"message_text": "W. X. Li, S. J. Xue, (NAOC), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report:\nFollowing the detection of the fast X-ray transient EP240618a by the Einstein Probe (Sun et al., GCN 36690), we initiated observations of the fast X-ray transient location starting on June 18 at 7:43 UT (~2 hours after the trigger) in the r band. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at McDonald Observatory in USA.\nNo new optical source was detected in the co-added images within the EP/FXT error box down to ~21.5 mag.\nThese observations were taken as part of the Global Supernova Project.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36731.",
"published": "2024-06-22T09:48:57.643652Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-22T09:48:57.643665Z",
"modified": "2024-06-22T09:48:57.649506Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 59098,
"topic": "gcn.circular",
"uuid": "f8ccf9c1-5863-4db3-9699-2a823c7b009a",
"title": "EP240618a: NOT further optical observations",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/06/23 02:56:10 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36741"
},
"title": "GCN CIRCULAR",
"number": "36741",
"subject": "EP240618a: NOT further optical observations"
},
"message_text": "X. Liu, S.Y. Fu, J. An, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC), M. Turkki (NOT) report on behalf of a large collaboration:\n\nFollowing the first epoch of the observations of EP240618a (Sun et al., GCN 36690) at the the 2.56-m Nordic Optical Telescope (NOT, Liu et al., GCN 36736), we have carried out the second epoch at the NOT.\n\nObservations started at 2024-06-23T00:13:37, i.e., ~ 4.8 day after the EP trigger, and again 12x120 s Sloan z-filter images were obtained.\n\nThe candidate in the 1st epoch is clearly detected in the 2nd epoch with comparable brightness in z-band. Specifically, it has z = 21.03 +/- 0.05 in the 1st epoch and z = 21.05 +/- 0.06 mag in the 2nd epoch, more or less affected by the nearby bright star ~1.3 arcsec away and the photometric method.\n\nAs the candidate is probably mixed with the bright star in the Pan-STARRS image, we also measure the candidate+star in the NOT images. Both NOT epochs yield the same magnitude of z ~ 18.4 mag, being consistent with the value by Pan-STARRS.\n\nHence, we conclude that the candidate is likely not the counterpart of EP240618a.\n\nMeanwhile, we searched for other possible candidates by image subtraction of the two NOT epochs within the 30-arcsec EP/FXT error circle (Sun et al., GCN 36690). Neither uncatalogued optical transient nor apparent brightening of catalogued source is found.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36741.",
"published": "2024-06-23T02:56:20.916962Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-23T02:56:20.916974Z",
"modified": "2024-06-23T02:56:20.922903Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 58374,
"topic": "gcn.circular",
"uuid": "eaa12212-a132-4549-9e87-f798706a2059",
"title": "EP240618a: NOT optical counterpart candidate",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/06/22 18:53:13 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36736"
},
"title": "GCN CIRCULAR",
"number": "36736",
"subject": "EP240618a: NOT optical counterpart candidate"
},
"message_text": "X. Liu, S.Y. Fu, J. An, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC), J. Terwel (NOT) report on behalf of a large collaboration:\n\nWe observed the field of EP240618a detected by EP/WXT (Sun et al., GCN 36690) using the the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 00:07:28 UT on 2024-06-20, i.e., ~ 1.77 day after the EP trigger, and 12x120 s Sloan z-filter images were obtained.\n\nAn uncatalogued optical transient (OT), within the 30 arcsec EP/FXT error circle (Sun et al., GCN 36690), is detected in the stacked z-band image at coordinates:\n\nR.A. (J2000)= 18:46:35.78\nDec. (J2000)= +23:50:13.17\n\nwith an uncertainty of ~ 0.2 arcsec. The OT is 1.3 arcsec away from a nearby 18.4 magnitude star, and its preliminary photometry is z ~ 21 mag at 1.78 day since the EP trigger, calibrated against nearby Pan-STARRS stars and not corrected for Galactic extinction.\n\nThe OT is not detected by early TRT observation (Tinyanont et al., GCN 36710) down to R ~ 20.3 mag, and not by LCO observation (Li et al., GCN 36731) down to r ~ 21.5 mag.\n\nIf EP240618a is a GRB, the z-r color might indicate high redshift.\n\nA finding chart of the candidate is available at\n\nhttps://drive.google.com/file/d/1pPAKrFyVvk3D7QnpgCfBQHim1ieGQ8zq/view?usp=sharing\n\nA second epoch in z-band at the NOT has been scheduled for the night of June 22.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36736.",
"published": "2024-06-22T18:53:28.647331Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-22T18:53:28.647348Z",
"modified": "2024-06-22T18:53:28.653622Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 51542,
"topic": "gcn.circular",
"uuid": "3c748996-0c96-4f3f-9cbd-d1f1562b7008",
"title": "EP240618a: OHP/T193 MISTRAL i' and Y band upper limits",
"submitter": "Hop gcn.circular",
"authors": "Christophe Adami at LAM <christophe.adami@lam.fr>",
"data": {
"date": "24/06/19 19:11:32 GMT",
"from": "Christophe Adami at LAM <christophe.adami@lam.fr>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36702"
},
"title": "GCN CIRCULAR",
"number": "36702",
"subject": "EP240618a: OHP/T193 MISTRAL i' and Y band upper limits"
},
"message_text": "C. Adami (LAM/Pytheas/AMU), E. Le Flocâh (CEA Paris-Saclay), F. Fortin (IRAP, Toulouse), \nB. Schneider (MIT), J. Palmerio, A. Saccardi, S. Vergani (GEPI/Obs. de Paris), M. Dennefeld (IAP), \nJ. Schmitt, E. Schmitt, E. Molina (OHP/Pytheas), F. Schussler (DPhP CEA), \nreport on behalf of a larger collaboration:\n\nWe observed the field of EP240618a (GCN 36690; Sun et al., GCN 36701; Wu et al.) using the T193cm \ntelescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We \nobtained 5400s (9x600s with dithering) in the Y-band between 21h13 and 22h47 UT on the 2024-06-18 \n(~16h after trigger) and 3900s (13x300s with dithering) in the i'-band between 22h53 on the 2024-06-\n18 and 00h18 UT on the 2024-06-19 (~18h after trigger).\n\nWe do not detect any significant new objects in our MISTRAL images within the X-ray position \nuncertainty area, nor in i band (3-sigma detection limit of 20.9) or Y band (3-sigma detection limit \nof 19.85). We however have a hint of a detection close to the ~2-sigma detection limit in the \nMISTRAL Y-band image at an approximate magnitude of Y~20.3 (with a large error bar) and located at \n18:46:36.3, +23:49:55.2. This putative source is not visible at all in the MISTRAL i-band image.\nWe encourage further deeper follow-ups of this possible source to assess its existence.\n\nThe photometric calibration was performed using nearby stars from the PanSTARRS catalog and the \nmagnitudes are not corrected for Galactic extinction.\n\nWe acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean \nPierre Troncin for the MISTRAL observations.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36702.",
"published": "2024-06-19T19:11:44.468210Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-19T19:11:44.468230Z",
"modified": "2024-06-19T19:11:44.472306Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 55232,
"topic": "gcn.circular",
"uuid": "71eacf56-398b-40f5-9dbd-cb357f377821",
"title": "EP240618a: Swift/XRT upper limit",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/21 10:21:36 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36723"
},
"title": "GCN CIRCULAR",
"number": "36723",
"subject": "EP240618a: Swift/XRT upper limit"
},
"message_text": "W. Chen, H. Sun (NAOC, CAS), H. Zhou (PMO, CAS), W. D. Zhang, D. Y. Li, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240618a by the Einstein Probe (Sun et al., GCN 36690), we triggered a Swift target of opportunity observation (ObsID: 00016670001). The XRT onboard Swift began the observation at 2024-06-20T15:56:06 UTC, about 58 hours after the WXT detection, with an exposure time of 2.0 ks in the Photon Counting mode.\n\nNo significant X-ray source was detected within the 30 arcsec region around the reported FXT position. Assuming an absorbed power-law model with a Galactic column density of 1.98 x 10^21 cm^-2 and a photon index of 2, the estimated flux upper limit in 0.3-10 keV at the 90% confidence level is 1.2 x 10^-13 ergs/cm^2/s.\n\nWe thank the Neil Gehrels Swift Observatory team for making the X-ray observation possible.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36723.",
"published": "2024-06-21T10:21:47.944815Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-21T10:21:47.944835Z",
"modified": "2024-06-21T10:21:47.948611Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 52390,
"topic": "gcn.circular",
"uuid": "e641fa73-61ca-4dba-94b0-4fc3ba2a08e7",
"title": "EP240618a: TRT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"data": {
"date": "24/06/20 02:58:48 GMT",
"from": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36710"
},
"title": "GCN CIRCULAR",
"number": "36710",
"subject": "EP240618a: TRT optical upper limit"
},
"message_text": "S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Q. Jiang, J. An, X. Liu, S.Y. Fu, Z.P. Zhu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of EP240618a (Sun et al., GCN 36690) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatory, California, USA. Observations started at 07:37:06.059 UTC on 2024-06-18, i.e., 1.89 hr after the EP trigger, and 15 x 120 s R-band frames were obtained.\n\nNo uncatalogued optical transient is detected in the stacked R-band image within the 30-arcsec EP/FXT error circle (Sun et al., GCN 36690), down to a 5-sigma limiting magnitude of R ~ 20.3, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for any catalogued source within the EP/FXT error circle.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36710.",
"published": "2024-06-20T02:58:58.964350Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-20T02:58:58.964370Z",
"modified": "2024-06-20T02:58:58.968254Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 63786,
"topic": "gcn.circular",
"uuid": "e90c4984-fff3-4223-a21c-41f3499591c9",
"title": "EP240625a: EP-FXT detection of the X-ray emission",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/25 16:02:06 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36760"
},
"title": "GCN CIRCULAR",
"number": "36760",
"subject": "EP240625a: EP-FXT detection of the X-ray emission"
},
"message_text": "X. Pan, Z. Z. Lv (NAOC, CAS), Y. C. Fu (BNU), Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240625a (Pan et al., GCN 36757), we performed an observation of EP240625a with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission. The observation began at 2024-06-25T03:10:00, about 1 hour after the EP-WXT detection. The exposure time is 5780 seconds. A slowly fading X-ray source was detected at R.A. = 310.7308 deg, DEC = -15.9760 deg, with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The spectrum can be fitted with an absorbed power-law model with NH fixed at the Galactic value of 3.85 x 10^20 cm^-2 and a photon index of 1.7(+/-0.4). The derived unabsorbed flux in 0.5-10 keV is 1.4(+0.8/-0.5) x 10^-13 erg/s/cm^2 (90% C.L.). There is no cataloged X-ray source within the error circle, suggesting this source being associated with EP240625a.\n\nPlease note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. Launched 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\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36760.",
"published": "2024-06-25T16:02:18.030590Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-25T16:02:18.030603Z",
"modified": "2024-06-25T16:02:18.037708Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 63561,
"topic": "gcn.circular",
"uuid": "59694212-d72d-4e18-902c-39c0a6f58222",
"title": "EP240625a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/25 11:04:29 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36757"
},
"title": "GCN CIRCULAR",
"number": "36757",
"subject": "EP240625a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "X. Pan, Z. Z. Lv (NAOC, CAS), Y. C. Fu (BNU), Y. Liu, Z. X. Ling, C. Zhang, C. C. Jin, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nWe report on the detection of a fast X-ray transient, designated EP240625a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient triggered the WXT on-board processing unit at 2024-06-25T01:48:23 (UTC). The position of the source is R.A. = 310.760 deg, DEC = -15.966 deg (J2000) with an uncertainty of 2 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for approximately 300 seconds and has a peak unabsorbed flux of ~1.3 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.8(+/-0.3) (with the column density fixed at the Galactic value of 3.85 x 10^20 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 2.9(+0.7/-0.5) x 10^-10 erg/s/cm^2. The uncertainties are at the 1 sigma level for the above parameters. No previously known X-ray sources at a similar flux level are found within the 2 arcmin region around the source position.\n\nFollowing the WXT detection, we performed a follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP. Further follow-up observations are encouraged to identify the nature of this X-ray transient.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36757.",
"published": "2024-06-25T11:04:40.187988Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-25T11:04:40.188003Z",
"modified": "2024-06-25T11:04:40.194147Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 66942,
"topic": "gcn.circular",
"uuid": "05eff416-a001-42b2-aa65-8494eca55ea9",
"title": "EP240625a: GRANDMA Optical Upper Limits",
"submitter": "Hop gcn.circular",
"authors": "Sarah Antier at OCA <sarah.antier@oca.eu>",
"data": {
"date": "24/06/27 09:44:18 GMT",
"from": "Sarah Antier at OCA <sarah.antier@oca.eu>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36771"
},
"title": "GCN CIRCULAR",
"number": "36771",
"subject": "EP240625a: GRANDMA Optical Upper Limits"
},
"message_text": "\nD. Akl (AUS), A. Le Calloch (Berkeley), Y.Rajabov (UBAI), M. Molham (KAO), S. Antier (OCA), S. Karpov (FZU), M. Coughlin (UMN), C. Andrade (UMN), I. Tosta e Melo (UniCT-DFA), P. Hello, N. Leroy (IJCLAB), P-A Duverne (APC), D. Turpin (CEA-Saclay/Irfu), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Masek (FZU), M. Prouza (FZU), A. Kaeouch (OUCA), M. Freeberg (KNC), N. Leroy (IJCLAB) on behalf of the GRANDMA collaboration:\n\nWe performed observations with GRANDMA and its citizen science project Kilonova-catcher (KNC) on the X-ray transient EP240625a detected by Einstein Probe (EP) WXT on T0 = 2024-06-25T01:48:23 (Pan et al., GCN 36757). We monitored the source with three telescopes, including FRAM-CTA-N, KNC-T32, KNC-ASO, from 2024-06-26T00:33:03.632 to 2024-06-26T16:15:48 UTC, starting 0.95 days after the EP trigger.\n\nWe did not find any new optical counterpart in any of our frames within 10 arcsec radius centered around Ra/Dec: 310.7308, -15.9760.\n\nAll our observations and upper limits, which correspond to the depth of the full image (given in the AB system), can be found here:\nhttps://skyportal-icare.ijclab.in2p3.fr/public/sources/EP240625a/version/fbcf272073852fb0c34826deb0914978\n\nBelow is the version that can be downloaded from the link above:\n+--------------+----------+----------------+-------------------+\n| MJD | Filter | Lim.Mag | Instrument |\n+==============+==========+================+===================+\n| 60487.008465 | L | 20.04 | KNC-ASO |\n+--------------+----------+----------------+-------------------+\n| 60487.061847 | G | 19.84 | KNC-ASO |\n+--------------+----------+----------------+-------------------+\n| 60487.034262 | R | 19.46 | KNC-ASO |\n+--------------+----------+----------------+-------------------+\n| 60487.091242 | B | 20.13 | KNC-ASO |\n+--------------+----------+----------------+-------------------+\n| 60487.182141 | R | 16.95 | FRAM-CTA-N |\n+--------------+----------+----------------+-------------------+\n| 60487.626447 | V | 19.88 | KNC-T32 |\n+--------------+----------+----------------+-------------------+\n\nWe note that bessellv and bessellr filters correspond to V and R Johnson Cousin filters, respectively.Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog while images taken with Sloan filters were calibrated using the Pan-STARRS DR1 Catalog.\n\nWe also note that some amateur telescopes use green filters, which were calibrated with the Gaia eDR3 catalog.Generic telescopes correspond to KNC telescopes.\n\nWe performed force photometry on our images at Ra, Dec: 20:42:55.47, -15:58:24.00 (S.Y. Fu et al., GCN 36761). We did not detect a source at that position at 20.7 upper limit in the V-band (Vega, 5 sigma).\n\nAll the data have been reduced by a single data processing pipeline STDPIPE (Karpov et al., 2022). We use the Skyportal application (skyportal.io) to monitor our observational campaign.\n\nWe thank the Einstein Probe team for useful communication.\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/).\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36771.",
"published": "2024-06-27T09:44:29.671311Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-27T09:44:29.671334Z",
"modified": "2024-06-27T09:44:29.676641Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 63787,
"topic": "gcn.circular",
"uuid": "6d3ba4b4-da34-4efa-89e6-af661eede847",
"title": "EP240625a: NOT optical counterpart candidate",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/06/25 16:25:42 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36761"
},
"title": "GCN CIRCULAR",
"number": "36761",
"subject": "EP240625a: NOT optical counterpart candidate"
},
"message_text": "S.Y. Fu, J. An, S.Q. Jiang, X. Liu, Z.P. Zhu, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), N. Koivisto (NOT) report on behalf of a large collaboration:\n\nWe observed the field of EP240625a detected by EP/WXT (Pan et al., GCN 36757) using the the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. We obtained 16x30 s Sloan z-filter images at a median time of 1.52 hr after the EP trigger.\n\nAn uncatalogued optical transient (OT), within the 10 arcsec EP/FXT error circle (Pan et al., GCN 36760), is marginally detected in the stacked z-band image at coordinates:\n\nR.A. (J2000)= 20:42:55.47\nDec. (J2000)= -15:58:24.00\n\nwith an uncertainty of ~ 0.2 arcsec. It has z = 20.7 +/- 0.2 mag , calibrated against nearby Pan-STARRS stars and not corrected for Galactic extinction. Given the low S/N for the OT, we cannot completely rule out it being due to background fluctuation.\n\nFurther observations are scheduled.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36761.",
"published": "2024-06-25T16:25:52.802987Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-25T16:25:52.803001Z",
"modified": "2024-06-25T16:25:52.811657Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 65779,
"topic": "gcn.circular",
"uuid": "f36c9c76-4e85-4857-a025-617e5d4b2610",
"title": "EP240626a: BOOTES-7 optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "ipg@iaa.es",
"data": {
"date": "24/06/26 20:28:27 GMT",
"from": "ipg@iaa.es",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36767"
},
"title": "GCN CIRCULAR",
"number": "36767",
"subject": "EP240626a: BOOTES-7 optical upper limit"
},
"message_text": "I. Perez-Garcia, S.-Y. Wu, , E. Fernandez-Garcia, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar, A. Castellon, A. Reina (Univ. de Malaga),Y.-D. Hu (INAF-OAB, Brera), L. Hernandez-Garcia (Univ. de Valparaiso), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:\n\nFollowing the detection of the fast X-ray transient EP240626a by the Einstein Probe (Wu et al. GCNC 36766), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) observed the fast X-ray transient location starting on June 26, 08:11 UT (~ 1.7 h after trigger) in different optical bands. Conditions were non-optimal as the target was at low altitude above horizon (and setting). No new optical source is detected on the co-added images (clear-filter) within the EP/WXT 2 arcmin radius error box down to 19.0 mag.\n\nWe thank the staff at San Pedro de Atacama Celestial Explorations observatory for their excellent support.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36767.",
"published": "2024-06-26T20:28:42.793071Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-26T20:28:42.793082Z",
"modified": "2024-06-26T20:28:42.797937Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 66596,
"topic": "gcn.circular",
"uuid": "0244a2fe-e94a-4407-8054-7df72549c42e",
"title": "EP240626a: EP-FXT detection of the X-ray emission",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/27 05:45:49 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36770"
},
"title": "GCN CIRCULAR",
"number": "36770",
"subject": "EP240626a: EP-FXT detection of the X-ray emission"
},
"message_text": "Q.Y. Wu, Z. Z. Lv (NAOC, CAS), Q. C. Shui (IHEP, CAS), Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240626a (Wu et al., GCN 36766), we performed an observation of EP240626a with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission. The observation began at 2024-06-26T08:58:37 (UTC), about 2.5 hours after the EP-WXT trigger. The exposure time is 6266 seconds. A faint source was detected at R.A. = 263.0171 deg, DEC = -13.0490 deg, with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic). The spectrum can be fitted with an absorbed power-law model with a photon index of 1.2(+0.7/-0.6) and the column density fixed at the Galactic value of 1.8 x 10^21 cm^-2. The derived unabsorbed flux in 0.5-10 keV is 1.5(+1.2/-0.7) x 10^-13 erg/s/cm^2 (90% C.L.). There is no cataloged X-ray source within the error circle, suggesting this source being associated with EP240626a.\n\nPlease note that EP-FXT is currently undergoing in-flight calibration. The derived source parameters may be subject to larger uncertainties, so please use them with caution. Launched 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\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36770.",
"published": "2024-06-27T05:46:00.372935Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-27T05:46:00.372950Z",
"modified": "2024-06-27T05:46:00.416822Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 65140,
"topic": "gcn.circular",
"uuid": "2c999143-a5f0-41b3-b8c3-2ee290dc023c",
"title": "EP240626a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/06/26 11:43:10 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36766"
},
"title": "GCN CIRCULAR",
"number": "36766",
"subject": "EP240626a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "Q.Y. Wu(NAOC, CAS), Q. C. Shui (IHEP, CAS), Z.Z. Lv, Z. X. Ling, Y. Liu, C. Zhang, C. C. Jin, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n\nWe report on the detection of a fast X-ray transient, designated EP240626a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2024-06-26T06:28:28 (UTC) and triggered the WXT on-board processing unit. The position of the source is R.A. = 263.023 deg, DEC = -13.051 deg (J2000) with an uncertainty of 2 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for approximately 160 seconds and has a peak unabsorbed flux of ~6 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 0.95(+/-0.54) and the column density fixed at the Galactic value of 1.8 x 10^21 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 1.70(+0.73/-0.50) x 10^-9 erg/s/cm^2. The uncertainties are given at the 90% confidence level for the above parameters. No previously known X-ray sources at a similar flux level are found within the 2 arcmin region around the source position.\n\nFollowing the WXT detection, we performed a follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP. Further follow-up observations are encouraged to identify the nature of this X-ray transient.\n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36766.",
"published": "2024-06-26T11:43:21.374961Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-26T11:43:21.374984Z",
"modified": "2024-06-26T11:43:21.389603Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 67499,
"topic": "gcn.circular",
"uuid": "c828099e-2ef1-49c8-a6d2-f49075441ea5",
"title": "EP240626a: KAIT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Weikang Zheng at UC Berkeley <weikang@berkeley.edu>",
"data": {
"date": "24/06/27 14:49:19 GMT",
"from": "Weikang Zheng at UC Berkeley <weikang@berkeley.edu>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36773"
},
"title": "GCN CIRCULAR",
"number": "36773",
"subject": "EP240626a: KAIT optical upper limit"
},
"message_text": "WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and\nAlexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:\n\nThe 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at\nLick Observatory, responded to the fast X-ray transient EP240626a\nfrom the Einstein Probe (Wu et al. GCNC 36766) starting at 1.01 hours\nafter the trigger. A set of 30x60s images were obtained in the clear\n(roughly R) filters. Preliminary analysis do not reveal any optical\ncounterpart candidate within the EP-FXT position error circle\n(Wu et al. GCNC 36770), neither in single image, nor in the co-add\nimages. The typical limiting magnitude of our single clear image is\nabout 19.0 mag calibrated to the PS1 catalog.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36773.",
"published": "2024-06-27T14:49:36.334636Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-27T14:49:36.334649Z",
"modified": "2024-06-27T14:49:36.339547Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 67824,
"topic": "gcn.circular",
"uuid": "50fb7492-078b-4af0-901c-ff150739d09d",
"title": "EP240626a: Montarrenti Observatory optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini@iol.it>",
"data": {
"date": "24/06/27 22:11:13 GMT",
"from": "Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini@iol.it>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36774"
},
"title": "GCN CIRCULAR",
"number": "36774",
"subject": "EP240626a: Montarrenti Observatory optical upper limit"
},
"message_text": "S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy) and B. De Simone (Universita' degli Studi Di Salerno) report:\n\nwe observed the field of the possible optical countepart of the X-ray transient EP240626a (Einstein Probe, GCN 36766, Wu et al.; GCN 36767, Perez-Garcia et al.; GCN 36773, Zheng et al.) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88).\n\nThe observations were started at 2024-06-26 21:22:28 UT (approximately 15 hours after the discovery of the X-ray transient) stacking 24x40s Rc-band CCD images.\n\nWe have not found any optical transient candidate within the error-box of the EP mission position with the following upper limit:\n\nMJD Filter Limit\n60488.3964 Rc > 19.40\n\nMagnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36774.",
"published": "2024-06-27T22:11:24.137236Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-06-27T22:11:24.137249Z",
"modified": "2024-06-27T22:11:24.143064Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 161148,
"topic": "gcn.circulars",
"uuid": "4e5c26c3-be60-4dba-acb3-c39379286a96",
"title": "EP240702a: 7DT Optical upper limits",
"submitter": "Gregory Paek at Seoul National University <gregorypaek94@gmail.com>",
"authors": "Gregory Paek at Seoul National University <gregorypaek94@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/38725"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.2.0/gcn/circulars.schema.json",
"eventId": "EP240702a",
"subject": "EP240702a: 7DT Optical upper limits",
"createdOn": 1735555648806,
"submitter": "Gregory Paek at Seoul National University <gregorypaek94@gmail.com>",
"circularId": 38725,
"submittedHow": "web"
},
"message_text": "Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), and Ji Hoon Kim (SNU ARC/SNU) report on behalf of the 7-Dimensional Telescope collaboration\n\nWe searched for the optical counterpart of a fast X-ray transient, EP240702a (Chen et al., GCN #36801) using the 7-Dimensional Telescopes (7DT). Approximately 26 hours following the initial detection (2024-07-02T00:50:05 UTC), we targeted the localization center provided by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at RA, Dec = 328.203 deg, -38.980 deg with an uncertainty of 3 arcmins. Observations were made with eleven 7DT units in twenty medium-band filters, denoted as m400, m425, then through m875, in which the numeric values indicate their central wavelengths in nanometers. Each medium-band filter has a bandwidth of 25nm.\n\nNo significant transient event was identified in the preliminary result. Photometric flux calibration was performed using synthetic photometries derived from the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. The 5-sigma upper limits (AB) range from 16.3 to 19.6 mag in the medium-band filters. To improve the depth for detection, we combined all images taken with the medium-band filters from m400 to m875. The combined image was treated as an r-band equivalent, and photometric measurements were performed. This approach yielded a 5-sigma upper limit of 20.2 AB magnitudes. Despite the increased depth, no significant transient detection was identified. Observations were conducted under suboptimal conditions, potentially limiting our search sensitivity.\n------\nFilter Date-obs[UT] Exp.time[s] Depth(5sigma)\nm400 2024-07-03T03:01:13.000 300 19.181\nm425 2024-07-03T03:06:51.000 300 19.510\nm450 2024-07-03T03:01:15.000 300 19.643\nm475 2024-07-03T03:06:45.000 300 18.943\nm500 2024-07-03T03:01:13.000 300 19.643\nm525 2024-07-03T03:06:42.000 300 19.497\nm550 2024-07-03T03:01:13.000 300 18.947\nm575 2024-07-03T03:06:41.000 300 19.092\nm600 2024-07-03T03:01:19.000 300 19.009\nm625 2024-07-03T03:06:53.000 300 18.688\nm650 2024-07-03T03:01:14.000 300 18.777\nm675 2024-07-03T03:06:42.000 300 18.853\nm700 2024-07-03T03:01:08.000 300 18.502\nm725 2024-07-03T03:06:34.000 300 18.062\nm750 2024-07-03T03:01:15.000 300 17.998\nm775 2024-07-03T03:06:43.000 300 17.450\nm800 2024-07-03T03:01:19.000 300 17.131\nm825 2024-07-03T03:06:44.000 300 16.989\nm850 2024-07-03T03:01:15.000 300 16.692\nm875 2024-07-03T03:06:42.000 300 16.306\n\nThe 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at http://gwuniverse.snu.ac.kr/.",
"published": "2024-12-30T10:47:37.350641Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2024-12-30T10:47:37.350654Z",
"modified": "2024-12-30T10:47:37.358092Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 168874,
"topic": "gcn.circulars",
"uuid": "10669277-f55d-4b94-9f4d-03818b5b3bda",
"title": "EP240702a: 7DT Optical upper limits",
"submitter": "Gregory Paek at Seoul National University <gregorypaek94@gmail.com>",
"authors": "Gregory Paek at Seoul National University <gregorypaek94@gmail.com>",
"data": {
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/38725"
},
"format": "text/plain",
"$schema": "https://gcn.nasa.gov/schema/v4.2.0/gcn/circulars.schema.json",
"bibcode": "2024GCN.38725....1P",
"eventId": "EP240702a",
"subject": "EP240702a: 7DT Optical upper limits",
"createdOn": 1735555648806,
"submitter": "Gregory Paek at Seoul National University <gregorypaek94@gmail.com>",
"circularId": 38725,
"submittedHow": "web"
},
"message_text": "Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), and Ji Hoon Kim (SNU ARC/SNU) report on behalf of the 7-Dimensional Telescope collaboration\n\nWe searched for the optical counterpart of a fast X-ray transient, EP240702a (Chen et al., GCN #36801) using the 7-Dimensional Telescopes (7DT). Approximately 26 hours following the initial detection (2024-07-02T00:50:05 UTC), we targeted the localization center provided by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at RA, Dec = 328.203 deg, -38.980 deg with an uncertainty of 3 arcmins. Observations were made with eleven 7DT units in twenty medium-band filters, denoted as m400, m425, then through m875, in which the numeric values indicate their central wavelengths in nanometers. Each medium-band filter has a bandwidth of 25nm.\n\nNo significant transient event was identified in the preliminary result. Photometric flux calibration was performed using synthetic photometries derived from the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. The 5-sigma upper limits (AB) range from 16.3 to 19.6 mag in the medium-band filters. To improve the depth for detection, we combined all images taken with the medium-band filters from m400 to m875. The combined image was treated as an r-band equivalent, and photometric measurements were performed. This approach yielded a 5-sigma upper limit of 20.2 AB magnitudes. Despite the increased depth, no significant transient detection was identified. Observations were conducted under suboptimal conditions, potentially limiting our search sensitivity.\n------\nFilter Date-obs[UT] Exp.time[s] Depth(5sigma)\nm400 2024-07-03T03:01:13.000 300 19.181\nm425 2024-07-03T03:06:51.000 300 19.510\nm450 2024-07-03T03:01:15.000 300 19.643\nm475 2024-07-03T03:06:45.000 300 18.943\nm500 2024-07-03T03:01:13.000 300 19.643\nm525 2024-07-03T03:06:42.000 300 19.497\nm550 2024-07-03T03:01:13.000 300 18.947\nm575 2024-07-03T03:06:41.000 300 19.092\nm600 2024-07-03T03:01:19.000 300 19.009\nm625 2024-07-03T03:06:53.000 300 18.688\nm650 2024-07-03T03:01:14.000 300 18.777\nm675 2024-07-03T03:06:42.000 300 18.853\nm700 2024-07-03T03:01:08.000 300 18.502\nm725 2024-07-03T03:06:34.000 300 18.062\nm750 2024-07-03T03:01:15.000 300 17.998\nm775 2024-07-03T03:06:43.000 300 17.450\nm800 2024-07-03T03:01:19.000 300 17.131\nm825 2024-07-03T03:06:44.000 300 16.989\nm850 2024-07-03T03:01:15.000 300 16.692\nm875 2024-07-03T03:06:42.000 300 16.306\n\nThe 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at http://gwuniverse.snu.ac.kr/.",
"published": "2025-01-20T08:08:16.924545Z",
"message_parser": "GCN Circular Parser v2",
"retracted": false,
"created": "2025-01-20T08:08:16.924556Z",
"modified": "2025-01-20T08:08:16.929321Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 75900,
"topic": "gcn.circular",
"uuid": "176ad3a0-d476-4dec-9074-44dc61b36564",
"title": "EP240702a: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/07/02 09:10:43 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36801"
},
"title": "GCN CIRCULAR",
"number": "36801",
"subject": "EP240702a: EP-WXT detection of a fast X-ray transient"
},
"message_text": "W. Chen (NAOC, CAS), C. Y. Dai (NJU), S. X. Wen, Z. X. Ling, W. Yuan, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n\nWe report on the detection of a fast X-ray transient, designated EP240702a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2024-07-02T00:50:05 (UTC) and triggered the WXT on-board processing unit. The position of the source is R.A. = 328.203 deg, DEC = -38.980 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The transient event lasts for approximately 50 seconds and has a peak absorbed flux of ~1.2 x 10^-8 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.1(+/-0.2) (with the column density fixed at the Galactic value of 2.0 x 10^20 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 5.4(+1.5/-1.2) x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. \n\nWe triggered a Swift target of opportunity observation. Further follow-up observations are encouraged to identify the nature of this X-ray transient. \n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36801.",
"published": "2024-07-02T09:10:57.764661Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-02T09:10:57.764675Z",
"modified": "2024-07-02T09:10:57.772435Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 76680,
"topic": "gcn.circular",
"uuid": "8154f3fd-2720-4245-b485-a204e279bf68",
"title": "EP240702a: GSP optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/07/03 04:26:38 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36806"
},
"title": "GCN CIRCULAR",
"number": "36806",
"subject": "EP240702a: GSP optical upper limit"
},
"message_text": "W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report:\nFollowing the detection of the fast X-ray transient EP240702a by the Einstein Probe (Chen et al., GCN 36801), we initiated observations of the fast X-ray transient location starting on July 2 at 6:10 UT (~5 hours after the trigger) in the r band. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at Cerro Tololo Inter-American Observatory in Chile.\nNo new optical source was detected in the co-added images within the EP/WXT error box down to ~21.5 mag.\nThese observations were taken as part of the Global Supernova Project.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36806.",
"published": "2024-07-03T04:26:50.347073Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-03T04:26:50.347089Z",
"modified": "2024-07-03T04:26:50.353339Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 77180,
"topic": "gcn.circular",
"uuid": "7a21c837-5ebc-47dd-80bf-49cf4ad6adc6",
"title": "EP240702a: Swift/XRT upper limit",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/07/03 13:31:10 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36808"
},
"title": "GCN CIRCULAR",
"number": "36808",
"subject": "EP240702a: Swift/XRT upper limit"
},
"message_text": "W. Chen, X. P. Xu (NAOC, CAS), C. Y. Dai (NJU), S. X. Wen, Z. X. Ling, W. Yuan, Y. Liu, C. Zhang, C. C. Jin, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team\n\nFollowing the detection of the fast X-ray transient EP240702a by the Einstein Probe (Chen et al., GCN 36801), we performed a Swift target of opportunity observation (ObsID: 00016693001). The XRT onboard Swift began the observation at 2024-07-02T09:03:28 UTC, about 8 hours after the WXT detection, with an exposure time of 1950 s in the Photon Counting mode.\n\nNo significant X-ray source was detected within the 3 arcmin region around the WXT position. Assuming an absorbed power-law model with a Galactic column density of 2.0 x 10^20 cm^-2 and a photon index of 1.1, the estimated flux upper limit in 0.3-10 keV at the 90% confidence level is 1.58 x 10^-13 ergs/cm^2/s.\n\nWe thank the Neil Gehrels Swift Observatory team for making the X-ray observation possible.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36808.",
"published": "2024-07-03T13:31:21.150638Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-03T13:31:21.150666Z",
"modified": "2024-07-03T13:31:21.162226Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 80937,
"topic": "gcn.circular",
"uuid": "4aaf593d-515c-421b-b4aa-353b1701761a",
"title": "EP240702a: TRT optical upper limits",
"submitter": "Hop gcn.circular",
"authors": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"data": {
"date": "24/07/05 15:23:17 GMT",
"from": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36831"
},
"title": "GCN CIRCULAR",
"number": "36831",
"subject": "EP240702a: TRT optical upper limits"
},
"message_text": "S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Q. Jiang, J. An, X. Liu, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of EP240702a (Chen et al., GCN 36801) using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Spring Brook Observatory, Australia. Observations started at 14:09:46 UTC on 2024-07-03, i.e., 1.55 day after the EP trigger, and 5 x 360 s frames in R- & I-band were obtained, respectively.\n\nNo uncatalogued optical transient is detected in the stacked images within the 3-arcmin EP/WXT error circle, down to 5-sigma limiting magnitudes of R ~ 21.8 and I ~ 20.7, calibrated with SkyMapper sources in the field.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36831.",
"published": "2024-07-05T15:23:24.571475Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-05T15:23:24.571493Z",
"modified": "2024-07-05T15:23:24.581216Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 80297,
"topic": "gcn.circular",
"uuid": "2b24aefe-b248-4d17-978e-d8b958e22a70",
"title": "EP240703a and EP240703b: Swift/XRT upper limits",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/07/05 08:51:47 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36827"
},
"title": "GCN CIRCULAR",
"number": "36827",
"subject": "EP240703a and EP240703b: Swift/XRT upper limits"
},
"message_text": "Q. C. Shui, J. Q. Peng (IHEP, CAS), C. Y. Dai (NJU), Y. L. Wang, C. C. Jin, Z. X. Ling, W. Yuan, Y. Liu, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, S. X. Wen, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n \nFollowing the detection of the fast X-ray transients EP240703a (Wang et al., GCN 36807) and EP240703b (Peng et al., GCN 36810) by the Einstein Probe, we triggered two Swift target of opportunity observations, one for each source.\n\nThe Swift observation of EP240703a (observation ID: 00016698001) began at 2024-07-03T18:16:06, about 17.5 hours after the WXT detection, with an exposure time of 1845 s in the Photon Counting mode. No significant X-ray source was detected within the 3 arcmin region around the WXT position of EP240703a. Assuming an absorbed power-law model with a Galactic column density of 5.68 Ã 10^21 cm^-2 and a photon index of 1.0, the estimated flux upper limit in 0.3-10 keV at the 90% confidence level is 1.62 Ã 10^-13 erg/cm^2/s.\n\nThe Swift observation of EP240703b (observation ID: 00016699001) began at 2024-07-03T19:58:00, about 14.5 hours after the WXT detection, with an exposure time of 1738 s in the Photon Counting mode. No significant X-ray source was detected within the 3 arcmin region around the WXT position of EP240703b. Assuming an absorbed power-law model with a Galactic column density of 9.52 Ã 10^20 cm^-2 and a photon index of 1.0, the estimated flux upper limit in 0.3-10 keV at the 90% confidence level is 1.06 Ã 10^-13 erg/cm^2/s.\n\nWe thank the Neil Gehrels Swift Observatory team for making the X-ray observations possible. \n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36827.",
"published": "2024-07-05T08:51:58.651254Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-05T08:51:58.651286Z",
"modified": "2024-07-05T08:51:58.658178Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 79124,
"topic": "gcn.circular",
"uuid": "83edda51-7ea1-4555-a319-eea435fd05b6",
"title": "EP240703a: BOOTES-3 optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"data": {
"date": "24/07/04 19:24:51 GMT",
"from": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36822"
},
"title": "GCN CIRCULAR",
"number": "36822",
"subject": "EP240703a: BOOTES-3 optical upper limit"
},
"message_text": "E. Fernandez-Garcia, I. Perez-Garcia, S.-Y. Wu, A. J. Castro-Tirado, M. D. Caballero-Garcia, I, Olivares, R. Sanchez-Ramirez and S. Guziy (IAA-CSIC), Y.-D. Hu (INAF-OAB), A. Castellon, S. Castillo, A. Reina and C. Perez del Pulgar (Univ. de Malaga), Ph. Yock (Univ. of Auckland), and R. Querel (NIWA), on behalf of a larger collaboration, report:\n\nFollowing the detection of EP240703a by EP-WXT (Wang et al., GCNC 36807) and Konus-Wind (Frederiks et al., GCNC 36809), we triggered the 60cm BOOTES-3/YA robotic telescope at NIWA Lauder in Otago (New Zealand) to observe the fast X-ray transient location on Jul. 3 at 14:28 UT (13.9 hrs after the detection). No new optical source is detected on the co-added images (60 x 30 s, clear-filter) within the 3 arcmin radius EP error box (Wang et al. GCNC 36807) down to 20.5 mag, which is consistent with the reports from Kinder (Aryan et al. GCNC 36819), TRT (An et al. GCNC 36820) and LT (Bochenek and Perley GCNC 36821) later on.\n\nWe thank the staff at NIWA at Lauder for its excellent support and especially to Bill Allen (1940-2023) for his invaluable contribution in the early times at the Blenheim site where our former BOOTES-3 station was initially deployed on his vineyard (until it was moved to Lauder in 2014). Bill Allen, a vintner (besides an engineer & astronomer!) remains in our hearts and we remember him every night we are looking to the heavens thru our Yock-Allen (YA) robotic telescope at the new BOOTES-3 station.\n\n\n\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36822.",
"published": "2024-07-04T19:25:01.850408Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-04T19:25:01.850424Z",
"modified": "2024-07-04T19:25:01.856768Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 79375,
"topic": "gcn.circular",
"uuid": "f410f345-ddd6-4041-a01d-4bca5e56e2f0",
"title": "EP240703a: BTA observations",
"submitter": "Hop gcn.circular",
"authors": "Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>",
"data": {
"date": "24/07/04 22:54:06 GMT",
"from": "Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36824"
},
"title": "GCN CIRCULAR",
"number": "36824",
"subject": "EP240703a: BTA observations"
},
"message_text": " A. Volnova (IKI), A. Moskvitin (SAO RAS), A. Pozanenko (IKI), D. Oparin\n(SAO RAS), N. Pankov (IKI, HSE), S. Belkin (IKI, HSE) on behalf of GRB IKI\nFuN report:\n\nWe observed the TRT candidate afterglow position (An et al., GCN 36815) of\nthe X-ray transient EP240703a (Wang et al., GCN 36807) and probable\ngamma-ray burst GRB 240703A (Frederiks et al., GCN 36809) with BTA SAO RAS\ntelescope equipped with SCORPIO-1 camera in Ic filter starting on\n2024-07-03 (UT) 20:50:07, i.e. 0.856 days after burst.\nWe did not detect the TRT candidate afterglow (An et al., GCN 36815) which\nmight be a spurious event (An et al., GCN 36820). At the stacked images of\n9x180 s we obtained an upper limit of Ic= 24.6m (3 sigma). We cannot\nconfirm that the TRT afterglow candidate (An et al., GCN 36815) is real.\nOur result is consistent with reported results (Aryan et al., GCN 36819,\nBochenek and Perley GCN 36821; Fernandez-Garcia et al., GCN 36822).\n\nWe are grateful to the Directorate of the Special Astrophysical Observatory\nfor allocation of the TOO observation.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36824.",
"published": "2024-07-04T22:54:17.555791Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-04T22:54:17.555810Z",
"modified": "2024-07-04T22:54:17.561949Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 77003,
"topic": "gcn.circular",
"uuid": "d44b3a7d-f4a3-4a46-8f7d-ff8629db4fc1",
"title": "EP240703a: EP-WXT detection of a fast X-ray transient ",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/07/03 10:00:25 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36807"
},
"title": "GCN CIRCULAR",
"number": "36807",
"subject": "EP240703a: EP-WXT detection of a fast X-ray transient "
},
"message_text": "Y.L. Wang (NAOC, CAS), C. Y. Dai (NJU), J. Q. Peng, Q. C. Shui (IHEP, CAS), C. C. Jin, Z. X. Ling, W. Yuan, Y. Liu, C. Zhang, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, S. X. Wen, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n\nWe report on the detection of a fast X-ray transient, designated EP240703a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2024-07-03T00:38:40 (UTC). The position of the source is R.A. = 273.803 deg, DEC = -9.681 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The corresponding Galactic coordinates are l = 20.174, b = 3.521.\n\nThe transient lasted for approximately 300 seconds and had a peak absorbed flux of ~5 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a column density of 1.5(+0.7/-0.6) x 10^22 cm^-2 and a photon index of 2.0(+1.0/-0.9). The derived average unabsorbed 0.5-4 keV flux is 5.9(+8.6/-2.6) x 10^-9 erg/s/cm^2. If the column density is fixed at the Galactic value of 4.5Â x 10^21Â cm^-2, the derived photon index is 0.4(+/-0.3) and the average unabsorbed 0.5-4 keV flux is 2.5(+0.4/-0.3) x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. \n\nWe have triggered a Swift target of opportunity observation. Further follow-up observations are encouraged to identify the nature of this X-ray transient. \n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36807.",
"published": "2024-07-03T10:00:36.031234Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-03T10:00:36.031252Z",
"modified": "2024-07-03T10:00:36.038507Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 77369,
"topic": "gcn.circular",
"uuid": "11979a54-60cb-4ccf-bd3d-cd8610f31845",
"title": "EP240703a/GRB 240703A: TRT and JinShan decaying optical afterglow candidate",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/07/03 18:28:56 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36815"
},
"title": "GCN CIRCULAR",
"number": "36815",
"subject": "EP240703a/GRB 240703A: TRT and JinShan decaying optical afterglow candidate"
},
"message_text": "J. An, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of the X-ray transient, EP240703a, detected by EP/WXT (Wang et al., GCN 36807), and also by Konus-Wind (Frederiks et al., GCN 36809), thus confirming that it is likely GRB 240703A, using the Thai Response Telescope (TRT) SBO node and the JinShan 100C & 50A telescopes.\n\nImage subtraction of the stacked 5 x 360 s R-band TRT image against the PanSTARRS archival r-band image reveals multiple optical afterglow candidates, among which an uncatalogued optical transient (OT) is localized at coordinates\n\nR.A. (J2000) = 18:15:03.89\nDec. (J2000) = -09:42:02.96\n\nwith an uncertainty of ~ 0.5 arcsec. The OT has r ~ 20.4 +/- 0.1 mag at a median time of ~ 13.9 hr post-trigger, calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction of A_r ~ 3 mag.\n\nWe then obtained 10 x 300 s frames in the Sloan r-band and 10 x 300 s in the Sloan z-band at the JinShan 100C telescope. The OT is not detected in the stacked r-band image down to r ~ 22.2 mag at a median time of 16.07 hr post-trigger, also not detected in z-band down to z ~ 20.6 mag at a median time of 16.91 hr post-trigger, both calibrated with the nearby PanSTARRS field.\n\nThe presence and the decay of the OT make it an optical afterglow candidate of EP240703a/GRB 240703A.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36815.",
"published": "2024-07-03T18:29:07.700867Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-03T18:29:07.700884Z",
"modified": "2024-07-03T18:29:07.709516Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 78605,
"topic": "gcn.circular",
"uuid": "ad38a71c-8837-4647-91cc-0d0809441db6",
"title": "EP240703a/GRB 240703A: TRT optical candidate likely not real",
"submitter": "Hop gcn.circular",
"authors": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"data": {
"date": "24/07/04 10:42:33 GMT",
"from": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36820"
},
"title": "GCN CIRCULAR",
"number": "36820",
"subject": "EP240703a/GRB 240703A: TRT optical candidate likely not real"
},
"message_text": "J. An (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Q. Jiang, X. Liu, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:\n\nRegarding our previously reported afterglow candidate of EP240703a/GRB 240703A (An et al., GCN 36815), we have checked the five 360 s R-band TRT images one by one.\n\nFirst, the candidate is only present in one of the five images, and not in the other four images. Second, it looks sharper than its neighboring sources, although it does cover multiple pixels in the image. We thus re-did cosmic ray removal with a revised script, and this time the candidate basically disappeared while its neighboring sources were almost unaffected by the same cosmic ray removal process.\n\nWe thus conclude that the candidate is very likely not real.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36820.",
"published": "2024-07-04T10:42:44.125940Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-04T10:42:44.125965Z",
"modified": "2024-07-04T10:42:44.132997Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 79665,
"topic": "gcn.circular",
"uuid": "a119eada-591b-4cb8-89a3-a83fce57d010",
"title": "EP240703a: KAIT optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Weikang Zheng at UC Berkeley <weikang@berkeley.edu>",
"data": {
"date": "24/07/05 01:45:56 GMT",
"from": "Weikang Zheng at UC Berkeley <weikang@berkeley.edu>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36825"
},
"title": "GCN CIRCULAR",
"number": "36825",
"subject": "EP240703a: KAIT optical upper limit"
},
"message_text": "WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and\n\nAlexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:\n\n\nThe 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at\n\nLick Observatory, responded to the fast X-ray transient EP240703a\n\nfrom the Einstein Probe (Wang et al. GCNC 36807) starting at 1.28 days\n\nafter the trigger. A set of 30x60s images were obtained in the clear\n\n(roughly R) filters. Preliminary analysis do not reveal any optical\n\ncounterpart candidate within the 3 arcmin radius EP-WXT error box\n\n(Wang et al. GCN 36807) neither in single image, nor in the co-add\n\nimages, consistent with the reports from Aryan et al. (GCN 36819),\n\nAn et al. (GCN 36820), Bochenek & Perley (GCN 36821), Fernandez-Garcia\n\net al. (GCN 36822) and Volnova et al. (GCN 36824). The typical limiting\n\nmagnitude of our single clear image is about 19.0 mag.\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36825.",
"published": "2024-07-05T01:46:06.412309Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-05T01:46:06.412325Z",
"modified": "2024-07-05T01:46:06.420735Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 78586,
"topic": "gcn.circular",
"uuid": "9e17f06b-a7e4-4654-a152-a0ec3bcc0fa7",
"title": "EP240703a: Kinder optical follow-up observations",
"submitter": "Hop gcn.circular",
"authors": "Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>",
"data": {
"date": "24/07/04 10:31:37 GMT",
"from": "Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36819"
},
"title": "GCN CIRCULAR",
"number": "36819",
"subject": "EP240703a: Kinder optical follow-up observations"
},
"message_text": "A. Aryan (NCUIA), S. Yang (HNAS), T.-W. Chen, Y.-J. Yang, C.-S. Lin, M.-H. Lee, Y.-C. Pan, H.-Y. Hsiao, W.-J. Hou, C.-C. Ngeow, C.-H. Lai, A. Sankar.K, H.-C. Lin, J.-K. Guo (all NCUIA), S. J. Smartt (Oxford/QUB), H. F. Stevance, S. Srivastav, J. Gillanders, L. Rhodes (all Oxford), M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (IfA, University of Hawaii) report:\n\nWe observed the field of the fast X-ray transient EP240703a (Wang et al., GCN 36807) using the One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first LOT epoch of observations started at 12:48 UT on 03rd of July 2024 (MJD = 60494.540), 12.32 hrs after the EP trigger.\n\nWe utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. We subtracted the stacked images with the Pan-STARRS1 template image using hotpants (Becker A., 2015, ascl.soft. ascl:1504.004).\n\nWe do not detect the presence of the proposed optical transient source at R.A. = 18:15:03.89 and Dec. = -09:42:02.96, as reported by An et al., GCN 36815, in the difference and stacked images. Our observations were 1.58 hours before those of the TRT observations and reach 2 magnitudes deeper.\n\nHowever, we detect a slight enhancement in the brightness of the eclipsing binary, ZTF J181510.36-094110.1 (Chen et al. 2020, ApJS, 249, 18) in the difference image at R.A. = 18:15:10.36 and Dec. = -09:41:10.1, which is close to the reported coordinate of EP240703a being only 0.66 arcmin away.\n\nMorever, we utilized the python based package, AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform the PSF photometry on our stacked frame. The current magnitudes of the eclipsing binary in our stacked frame are r = 19.02 +/- 0.04 mag and i = 18.18 +/- 0.05 mag.\n\nBesides ZTF J181510.36-094110.1, we do not detect any new optical source in the reference and stacked frames. The details of the observations and measured 3-sigma upper limit are as follow:\n\nTelescope | Filter | MJD (start) | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass\nLOT | r | 60494.540 | 12.32 hrs | 300 sec * 6 | > 22.3 | 1\".48 | 1.47\nLOT | i | 60494.598 | 13.72 hrs | 300 sec * 6 | > 21.8 | 1\".34| 1.22\n\nThe presented magnitudes are calibrated using the field stars from the Pan-STARRS1 catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 1.225 mag in the direction of the burst (Schlafly & Finkbeiner 2011).\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36819.",
"published": "2024-07-04T10:31:46.976986Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-04T10:31:46.977011Z",
"modified": "2024-07-04T10:31:46.983674Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 79022,
"topic": "gcn.circular",
"uuid": "04625a3e-d640-4fd3-9709-a4fcdc2e0fc1",
"title": "EP240703a: Liverpool Telescope optical follow-up observations",
"submitter": "Hop gcn.circular",
"authors": "A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>",
"data": {
"date": "24/07/04 17:53:09 GMT",
"from": "A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36821"
},
"title": "GCN CIRCULAR",
"number": "36821",
"subject": "EP240703a: Liverpool Telescope optical follow-up observations"
},
"message_text": "A. Bochenek and D. A. Perley (LJMU) report:\n\nWe observed the field of the X-ray transient and probable gamma-ray burst EP240703a (Wang et al., GCN 36807; Frederiks et al., GCN 36809) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x180s exposures with the SDSS-I filter between 2024-07-04 02:27:40 UT and 2024-07-04 02:45:02 UT, approximately 1.1 days after the transient.\n\nThe limiting magnitude of the stacked image is i > 21.9 mag (AB) for a three-sigma detection limit, with mid-observation time being 2024-07-04 02:34:51 UT. No new sources were identified within the 90% confidence 3 arcmin error circle compared to the Pan-STARRS catalogue. Additionally, no source was detected at the TRT candidate afterglow position (An et al., GCN 36815), now thought to be a probable cosmic ray (An et al., GCN 36820).\n\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36821.",
"published": "2024-07-04T17:53:24.577027Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-04T17:53:24.577043Z",
"modified": "2024-07-04T17:53:24.583564Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 80942,
"topic": "gcn.circular",
"uuid": "59c1ab25-de5d-44a3-86e5-6c857f71c692",
"title": "EP240703a: TRT further optical observation",
"submitter": "Hop gcn.circular",
"authors": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"data": {
"date": "24/07/05 15:25:25 GMT",
"from": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36832"
},
"title": "GCN CIRCULAR",
"number": "36832",
"subject": "EP240703a: TRT further optical observation"
},
"message_text": "S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, S.Q. Jiang, J. An, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of the fast X-ray transient EP240703a (Wang et al., GCN 36807) using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Spring Brook Observatory, Australia. Observations started at 10:16:15 UTC on 2024-07-04, i.e., 1.40 day after the EP trigger, and 5 x 360 s I-band frames were obtained.\n\nNo uncatalogued optical transient is detected in the stacked image within the 3-arcmin EP/WXT error circle, down to a 5-sigma limiting magnitude of I ~ 20.0, calibrated with Pan-STARRS sources in the field.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36832.",
"published": "2024-07-05T15:25:33.217787Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-05T15:25:33.217821Z",
"modified": "2024-07-05T15:25:33.224215Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 77299,
"topic": "gcn.circular",
"uuid": "e154f706-d5c5-4aaa-be28-ccd2f3ec485b",
"title": "EP240703b: EP-WXT detection of a fast X-ray transient",
"submitter": "Hop gcn.circular",
"authors": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"data": {
"date": "24/07/03 15:09:49 GMT",
"from": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36810"
},
"title": "GCN CIRCULAR",
"number": "36810",
"subject": "EP240703b: EP-WXT detection of a fast X-ray transient"
},
"message_text": "J. Q. Peng, Q. C. Shui (IHEP, CAS), C. Y. Dai (NJU), Y. L. Wang, C. C. Jin, Z. X. Ling, W. Yuan, Y. Liu, C. Zhang, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, S. X. Wen, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team \n\nWe report on the detection of a fast X-ray transient, designated EP240703b, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2024-07-03T05:24:26 (UTC). The position of the source is R.A. = 279.539 deg, DEC = -57.401 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The corresponding Galactic coordinates are l = 338.077, b = -20.878.\n\nThe transient lasted for approximately 600 seconds and had a peak absorbed flux of ~ 3 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a column density of 1.4(+1.3/-1.2) x 10^21 cm^-2 and a photon index of 1.5(+0.6/-0.5). The derived average unabsorbed 0.5-4 keV flux is 7.5(+1.3/-1.8) x 10^-10 erg/s/cm^2. If the column density is fixed at the Galactic value of 6.8Â x 10^20Â cm^-2, the derived photon index is 1.2(+/-0.2) and the average unabsorbed 0.5-4 keV flux is 7.1(+1.1/-1.0) x 10^-10 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. No previously known X-ray sources at a similar flux level are found within the 3 arcmin region around the source position. \n\nWe have proposed a Swift target of opportunity observation. Further follow-up observations are encouraged to identify the nature of this X-ray transient. \n\nThe above observation was made with the WXT instrument during the commissioning phase of EP. Launched 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.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36810.",
"published": "2024-07-03T15:10:04.110275Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-03T15:10:04.110292Z",
"modified": "2024-07-03T15:10:04.116786Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 84532,
"topic": "gcn.circular",
"uuid": "2972a917-8dea-4b99-bcce-5efe324fc3d5",
"title": "EP240703b: GSP optical upper limit",
"submitter": "Hop gcn.circular",
"authors": "Wenxiong Li <liwenxiong1992@gmail.com>",
"data": {
"date": "24/07/07 10:53:50 GMT",
"from": "Wenxiong Li <liwenxiong1992@gmail.com>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36836"
},
"title": "GCN CIRCULAR",
"number": "36836",
"subject": "EP240703b: GSP optical upper limit"
},
"message_text": "W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report:\nFollowing the detection of the fast X-ray transient EP240703b by the Einstein Probe (Peng et al., GCN 36810), we initiated observations of the fast X-ray transient location starting on July 4 at 6:01 UT (~24 hours after the trigger) in the r band. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at Cerro Tololo Inter-American Observatory in Chile.\nNo new optical source was detected in the co-added images within the EP/WXT error box down to ~21.0 mag.\nThese observations were taken as part of the Global Supernova Project.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36836.",
"published": "2024-07-07T10:54:04.916259Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-07T10:54:04.916276Z",
"modified": "2024-07-07T10:54:04.923505Z",
"nonlocalizedevents": [],
"targets": []
},
{
"id": 80943,
"topic": "gcn.circular",
"uuid": "9e2af3d8-71b6-4a00-be29-d6b7b598cd4c",
"title": "EP240703b: TRT optical upper limits",
"submitter": "Hop gcn.circular",
"authors": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"data": {
"date": "24/07/05 15:25:56 GMT",
"from": "S. Tinyanont at National Astronomical Research Institute of Thailand <samaporn@narit.or.th>",
"urls": {
"gcn_circular": "https://gcn.nasa.gov/circulars/36833"
},
"title": "GCN CIRCULAR",
"number": "36833",
"subject": "EP240703b: TRT optical upper limits"
},
"message_text": "S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, S.Q. Jiang, J. An, S.Y. Fu, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of the fast X-ray transient EP240703b (Peng et al., GCN 36810) using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Spring Brook Observatory, Australia. Observations started at 09:09:53 UTC on 2024-07-04, i.e., 1.16 day after the EP trigger, and 5 x 360 s frames in the R- & I- bands were obtained, respectively.\n\nNo uncatalogued optical transient is detected in the stacked image within the 3-arcmin EP/WXT error circle, down to a 5-sigma limiting magnitudes of R ~ 21.3 and I ~ 20.4, calibrated with SkyMapper sources in the field.\n\n\nView this GCN Circular online at https://gcn.nasa.gov/circulars/36833.",
"published": "2024-07-05T15:26:01.346881Z",
"message_parser": "GCN Circular Parser v1",
"retracted": false,
"created": "2024-07-05T15:26:01.347008Z",
"modified": "2024-07-05T15:26:01.364212Z",
"nonlocalizedevents": [],
"targets": []
}
]
}