{
  "eventId": "GRB 260504B",
  "body": "A. Saccardi (CEA/Irfu), D. Adrien (CEA/Irfu), F. Piron (LUPM), D. Gotz (CEA/Irfu), P. Maggi (ObAS), C. W. Wang (IHEP), Y. Wang (PMO,CAS; UCB), W. J. Xie (NAO,CAS), report on behalf of the SVOM mission team:\n\nAt 2026-05-04T09:31:19 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260504B (SVOM burst-id sb26050402).\n\nThe following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.\n\nThe burst was only detected by the Count-Rate Trigger (CRT), which produced a sequence of 6 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 17.15 in the [8-120] keV energy band over a time window of 0.30 seconds starting at 2026-05-04T09:31:19.\n\nThe localization of the best alert is R.A., Dec. 351.2451, -80.3291 degrees (J2000) with a 90% confidence level (C.L.) radius of 4.91 arcmin (including systematic error of 2 arcmin added in quadrature).\n\nThe SVOM/ECLAIRs light curve shows a single narrow peak structure with a T90 duration of 0.5 +/- 0.1 s (5-120 keV).\n\nThis burst also triggered SVOM/GRM at 2026-05-04T09:31:19 on a timescale of 0.10 seconds with an SNR of 31.30.\nThe SVOM/GRM light curve shows a single narrow peak structure with a T90 duration of 0.22 +/- 0.02 s (8-1100 keV).\n\nThe SVOM/GRM light curve can be found here：\nhttps://www.bursthub.cn//admin/static/svgrb260504B.png \n\nSVOM slewed to the burst.\n\nSVOM/MXT began observing the field at 2026-05-04T09:33:16 UTC, 117 seconds after T0. Using onboard processed data we found a possible uncatalogued X-ray source located at R.A., Dec.  351.285, -80.383 degrees:\nR.A. (J2000) = 23h25m08s\nDec. (J2000) = -80d22m59s\nwith a 90% C.L. radius of 167 arcseconds.\n\nThis location is 3.2 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.\n\nVT began observing the field after the slew. The analysis of the data will be published in a future circular.\n\nThe Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.\n\nThe Burst Advocate (BA) on shift for this alert is Yun Wang: wangyun@pmo.ac.cn.\nPlease contact the BA by email if you require additional information.\n",
  "format": "text/plain",
  "subject": "GRB 260504B: SVOM detection of a short burst",
  "editedOn": 1777918508541,
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>",
  "version": 2,
  "circularId": 44454,
  "createdOn": 1777888859104,
  "submittedHow": "web"
}