TITLE:   GCN CIRCULAR
NUMBER:  42742
SUBJECT: GRB 251116C: SVOM/ECLAIRs refined analysis
DATE:    25/11/18 18:41:49 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

M. Brunet, O. Godet (IRAP), W. Xie (NAOC), M. Pillas (IAP), M.G. Bernardini (INAF-OAB, LUPM),

Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 251116C (SVOM burst-id sb25111605, GCN 42703) detected at T0 = 2025-11-16T15:57:41, which was also detected by Swift/BAT (GCN 42726).

The burst that triggered ECLAIRs consists of a single peak lightcurve, lasting about 60 s in the 4-120 keV energy band. We note that the burst occurred close to the Earth limb and that it was quickly hidden behind the Earth after the trigger so that part of the emission might have been missed by ECLAIRs.

The time-averaged spectrum from T0-15 s to T0+39 s in the 5-120 keV energy range is best fitted by a power-law model with a photon index of 1.95 +/-0.10. With this model, the total 4-120 keV fluence is (1.2 +/-0.1) e-06 erg/cm^2.

Given the value of the photon index, the peak energy may be below 5keV, which would classify this GRB as an X-Ray Flash.

All the quoted errors are at the 68% confidence level.

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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC.

The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at irap.omp.eu)