GCN Circular 39662

C.W. Wang (IHEP), R.C. Chen (NJU), H. Goto, D. Turpin (CEA), M. G. Bernardini (INAF-OAB, LUPM) 
on behalf of the SVOM mission team.

At 2025-03-11T07:08:05.065 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250311B (SVOM burst-id sb25031101). 
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.

The burst was only detected by the Count rate Trigger (CRT), from which we received 1 alert. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 7.45 in the [8-120] keV energy band over a time window of 10.2 seconds starting at Tb.

The localization of the best alert is R.A., Dec 146.885, 29.891 degrees:
RA (J2000) = 9h47m32.36s
Dec (J2000) = 29d53m26.62s
with a 90% C.L. radius of 10.53 arcmin (including systematic error of 2 arcmin added in quadrature).

No immediate slew was performed on this burst. A SVOM ToO has been requested.

The 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.

The Burst Advocate (BA) on shift for this burst is C.W. Wang: cwwang@ihep.ac.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.