{
  "circularId": 40513,
  "format": "text/plain",
  "subject": "GRB 250521B: SVOM detection of a burst through offline search",
  "createdOn": 1747846238776,
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>",
  "bibcode": "2025GCN.40513....1F",
  "eventId": "GRB 250521B",
  "submittedHow": "web",
  "body": "\nA. Foisseau, C. Lachaud (APC), M. Brunet (IRAP), N. Dagoneau (CEA)\n\nreport on behalf of the SVOM team:\n\nThe SVOM/ECLAIRs telescope detected a transient source, labelled GRB 250521B, starting at 2025-05-21T04:19:17.8 UTC (Tb), through an offline search with the event-by-event data downloaded through the X-band ground station.\n\nThe burst was detected within several energy ranges in a 5.12 seconds timescale. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.2 within 8-50 keV over a time window of 5.12 seconds starting at Tb.\n\nThe lightcurve consists of a single pulse lasting around 5s.\n\nThe localization of the source is RA, Dec = 200.822, 1.766 degrees:\n\nRA (J2000) = 13h23m17.3s  \nDec (J2000) = 01d45m57.6s \n\nwith a 90% C.L. radius of 12.2 arcmin (including systematic error of 6 arcmin added in quadrature).\n\nWe note that no bright X-ray sources are found in the error box.\n\nThe Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP.\n\nThe SVOM point of contact for this event  is : A. Foisseau : foisseau@apc.in2p3.fr\n\nPlease contact him by email if you require additional information regarding the SVOM follow-up of this burst.\n\n"
}