{
  "format": "text/plain",
  "eventId": "GRB 250317B",
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>",
  "bibcode": "2025GCN.39753....1Z",
  "createdOn": 1742189396403,
  "body": "Donghua Zhao, Yinuo Ma, Wenjin XIE(NAOC), Li Zhang (IHEP), F. Robinet (IJCLab), Liping Xin (NAOC)\non behalf of the SVOM mission team.\n\nAt 2025-03-17T02:12:08 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250317B (SVOM burst-id sb25031701). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.\n\nThe burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 13 alerts. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 14.27 in the [5-8] keV energy band over a time window of 40.96 seconds starting at Tb.\nThe light curve showed a broad peak structure with a T90 duration of about 145.67 (-0.16 +0.16).\n\nThe localization of the best alert is R.A., Dec 211.665, 40.056 degrees (J2000) with a 90% C.L. radius of 5.75 arcmin (including systematic error of 2 arcmin added in quadrature).\n\nSVOM slewed to the burst.\n\nMXT began observing the field at 2025-03-17T02:14:36 UTC, 148 seconds after Tb. Using onboard processed data we found a bright and rapidly fainting uncatalogued X-ray source located at R.A., Dec 211.648, 40.057 degrees:\nRA (J2000) = 14h06m35s\nDEC (J2000) = 40d03m23s\nwith a 90% C.L. radius of 25 arcseconds.\nThis location is 48 arcseconds away from the ECLAIRs onboard position.\n\nVT began to observe the field after the slew. No uncatalogued sources were detected within MXT errors compared to DESI catalog based on the VHF sequences. The 3 sigma limit magnitude is about VT_R~21 mag (AB) at about 10 minutes after the trigger. More analysis will be performed after receiving the X band data later.\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.\n\nThe Burst Advocate (BA) on shift for this burst is Donghua Zhao (zhaodh@bao.ac.cn).\nPlease contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.\n\n\nWe apologize for any confusion and inconvenience caused by this mistake.",
  "subject": "GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752",
  "submittedHow": "web",
  "circularId": 39753
}