GCN Circular 42757

C. Wu (NAOC), K.X. Gong (CHO), D. Turpin, S. Schanne, D. Gotz (CEA), U. Jacob (LUPM) report on behalf of the SVOM mission team:

At 2025-11-19T08:47:44 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251119A (SVOM burst-id sb25111901).

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), which produced a sequence of 3 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.89 in the [5-8] keV energy band over a time window of 20.40 seconds starting at 2025-11-19T08:47:23 (Tb).

The localization of the best alert is R.A., Dec. 84.4289, 12.2431 degrees:
R.A. (J2000) = 5h37m42.93s
Dec. (J2000) = 12d14m35.17s
 with a 90% confidence level (C.L.) radius of 9.96 arcmin (including systematic error of 2 arcmin added in quadrature).

We notice that the Crab is located near the border of the field of view and about 9.8 degrees away from the burst’s position with a SNR of 9.0 (similar to the burst’s SNR) in the sky image.

SVOM slewed to the burst position.

SVOM/MXT began observing the field at 08:51:08 UTC, 206 seconds after T0. Using onboard processed data, no source was detected in 225 seconds.
The SVOM/MXT team is waiting for the full dataset to detect and localise the possible SVOM/MXT counterpart.

VT began observing the field after the slew. The analysis of the data will be published in a future circular.

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 Chao Wu: cwu@bao.ac.cn.
Please contact the BA by email if you require additional information.