GCN Circular 45517
Subject
GRB 260903A: SVOM/ECLAIRs refined analysis
Event
Date
2026-09-04T17:41:50Z (10 hours ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet, H. Yang, O. Godet (IRAP) , W.-J. Xie (NAOC), R.-C. Chen (NJU), T. Xiao (GXU), report on behalf of the SVOM/ECLAIRs team:
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260903A (SVOM burst-id sb26090302 – GCN 45499, trigger time T0 = 2026-09-03T12:37:20 UTC).
The burst that triggered ECLAIRs onboard shows a single peak lightcurve. The burst duration is T90 = 21 +6/-4 s in the 4-20 keV energy band.
The time-averaged spectrum from T0-18.98 s to T0+1.13 s in the 5-120 keV energy range is best fitted by a powerlaw model, with alpha = -3.2/-0.5. With this model, the 4-120 keV fluence is (1.6 +0.3/-0.2)e-7 erg/cm^2 and the 4-120 keV photon flux is 0.70 +/-0.08 ph/cm^2/s.
A blackbody model also gives a good fit with kT = 1.8 +/-0.2 keV. With this model, the 4-120 keV fluence is (1.2 +/-0.2)e-7 erg/cm^2 and the 4-120 keV photon flux is 0.54 +/-0.06 ph/cm^2/s.
The spectral parameters show that this burst could be classified as an X-Ray Flash (XRF).
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 et utoulouse.fr)