TITLE:   GCN CIRCULAR
NUMBER:  45333
SUBJECT: GRB 260808B: SVOM/ECLAIRs refined analysis
DATE:    26/08/09 19:10:45 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

Authors: M. Brunet, L. Bouchet, S. Guillot (IRAP), Michela Dinatolo (U. Milano)
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 260808B (SVOM burst-id sb26080812 – GCN 45316, trigger time T0 = 2026-08-08T14:20:58 UTC).

The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve with a possible precursor at T0-84.5 s lasting around 2 s. The burst duration is T90 = 178 +12/-8 s in the 4-120 keV energy band.

The time-averaged spectrum before the slew, from T0-45s to T0+43s in the 5-120 keV energy range is best fitted by a powerlaw model with alpha = -1.96 +0.14/-0.16. With this model, the 4-120 keV fluence is 6.4 +/-0.9 e-7  erg/cm^2 and the 4-120 keV photon flux is 0.32 +/-0.03 ph/cm^2/s. 

The possible precursor is too faint to extract any significant spectral parameters.

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: L. Bouchet (IRAP) (laurent.bouchet at utoulouse.fr)