TITLE:   GCN CIRCULAR
NUMBER:  42374
SUBJECT: GRB 251016A: SVOM/ECLAIRs refined analysis
DATE:    25/10/21 11:52:34 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

M. Brunet, O. Godet, S. Guillot (IRAP), B. Hubert (CEA), S.Basa, S.Boissier (LAM)

Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 251016A (SVOM burst-id sb2525101602, GCN 42308) detected at T0 = 2025-10-16T14:59:20, which was also detected by SVOM/GRM, Fermi/GBM (GCN 42309), CALET/GBM (GCN 42321), Glowbug (GCN 42313), AstroSat/CZTI (GCN 42327) and HXMT/HE (GCN 42359).

The burst that triggered ECLAIRs consists of a single short peak, with a duration of T90 = 0.69 +0.09/-0.19 s in the 4-120 keV energy band.

The time-averaged spectrum from the peak (T0-0.4 s to T0+0.4 s) in the 5-120 keV energy range is well fitted by a power-law model with a photon index of 1.00 +/-0.16, which is consistent with the results found by Smith at al. 2025 (GCN 42365). With this model, the total 4-120 keV fluence is (3.01 +0.27/-0.94) e-07 erg/cm^2 .

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).