GCN Circular 45692
Subject
GRB 260918A: SVOM/ECLAIRs refined analysis
Event
Date
2026-09-22T15:23:07Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet, H. Yang, O.Godet (IRAP), Yun Wang (UCB; PMO), Yehao Cheng(YNU)
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 260918A (SVOM burst-id sb26091801 – GCN 45619, trigger time T0 = 2026-09-18T03:47:56 UTC), which was also detected as a subthreshold by Fermi/GBM (GCN 45639).
The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve. The burst duration is T90 = 82 +28/-5s in the 4-120 keV energy band.
The refined burst localization is RA, Dec = 354.725, -8.909 degrees (J2000)
RA (J2000) = 23h38m54.0s
Dec (J2000) = -08d54m32.4s
with a 90% C.L. radius of 8.73 arcmin (including systematic error of 2 arcmin added in quadrature).
The time-averaged spectrum from T0-34 s to T0+36 s in the 5-120 keV energy range is best fitted by a powerlaw, model with alpha = -1.26 +0.12/-0.11. With this model, the 4-120 keV fluence is (8.9 +/-0.9)e-7 erg/cm^2 and the 4-120 keV photon flux is 0.29 +/- 0.3 ph/cm^2/s.
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 utoulouse.fr)