TITLE: GCN CIRCULAR NUMBER: 38845 SUBJECT: GRB 250108A: SVOM detection of a soft long burst DATE: 25/01/08 05:57:19 GMT FROM: Weikang Zheng at UC Berkeley weikang@berkeley.edu
W. Zheng (UCB), Z-Q. Wang (GXU), W.-J. XIE (NAOC, CAS), D.-H. ZHAO (NAOC, CAS), S. Guillot (IRAP), D. Götz (CEA), H. Goto (CEA), C-W. Wang (IHEP) report on behalf of the SVOM team.
The SVOM/ECLAIRs telescope triggered and located the long duration GRB 250108A (sb25010802) starting at 2025-01-08T04:37:01.513 UTC (Tb).
The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network.
The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 9 alerts were received. The best detection is obtained by IMT with a signal-to-noise ratio of 10.2 in the 5-8 keV energy band over a time window of 40.96 s starting at Tb. The light curve in ECLAIRs with a preliminary T90 duration is about 40 s.
The localization of the best Alert is RA, Dec = 207.946, 26.204 (J2000). The uncertainty on this position is 7.79 arcminutes at 90% C.L. which includes 2 arcminutes of systematic uncertainty in quadrature.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250108A.png
SVOM performed an automatic slew and MXT started observing the ECLAIRs error box at 04:40:49 UTC, i.e. 228 s after Tb. An uncatalogued X-ray source has been found by the on board software at R.A., Dec. = 207.906, 26.232 (J2000) (13:51:38, +26:13:56, J2000) with an uncertainty of 60 arc sec (90% C.L., including systematics). This source is located at 2.7 arc minutes from the ECLAIRs position.
VT results will be reported later.
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.
The SVOM point of contact for this burst is: Weikang Zheng ( weikang@berkeley.edu)
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