GCN Circular 39973

M. Brunet (IRAP), S. Schanne (CEA), J. Atteia (IRAP), C. W. Wang,  Y. Huang (IHEP), O. Godet (IRAP), D. Turpin (CEA)

report on behalf of the SVOM team:

The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 250320C, starting at 2025-03-20T17:39:40.0 UTC (Tb), through an offline search with the event-by-event data downloaded through the X-band ground station.

The burst was detected by several methods and within several energy ranges and timescales. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.7 within 4-120 keV over a time window of 40.96 seconds starting at 2025-03-20T17:40:39.4 UTC. 

The lightcurve shows a first episode, starting at Tb, composed of a single peak that lasted around 5s and a second episode 1 minute later composed of multiple peaks, that lasted around 40s.

The localization of the source is RA, Dec = 170.930, 40.677 (J2000). The uncertainty on this position is 11.6 arcminutes at 90% C.L.

We notice the presence of several quasars in this error box, among which the closest is SDSS J112340.66+404052.0 located at 0.5 arcmin. However the lightcurve is more suggestive of a GRB.

The 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.

The SVOM point of contact for this event  is: Marius Brunet (IRAP) marius.brunet@irap.omp.eu.
Please contact him by email if you require additional information regarding the SVOM follow-up of this burst.