GCN Circular 42976

M. Brunet, N. A. Webb  (IRAP), N. Dagoneau, M. Moita, D. Turpin (CEA) report on behalf of the SVOM mission team

At 2025-12-03T18:33:50 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251203C (SVOM burst-id sb25120305).

The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.

The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 11 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 11.74 in the [8-50] keV energy band over a time window of 10.20 seconds starting at 2025-12-03T18:33:45.

The localization of the best alert is R.A., Dec. 51.7804, -7.3100 degrees:
R.A. (J2000) = 3h27m07.31s
Dec. (J2000) = -7d18m36.09s
with a 90% confidence level (C.L.) radius of 6.85 arcmin (including systematic error of 2 arcmin added in quadrature).

No immediate slew was performed on this burst.
A SVOM ToO has been programmed for follow-up.

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. 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.

The Burst Advocate (BA) on shift for this alert is Marius Brunet: mbrunet@irap.omp.eu.
Please contact the BA by email if you require additional information.