TITLE:   GCN CIRCULAR
NUMBER:  43711
SUBJECT: GRB 260128B: SVOM/ECLAIRs refined analysis
DATE:    26/02/12 09:13:11 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

M. Brunet, O. Godet (IRAP), S. Le Stum, A. Coleiro (APC) on behalf of the ECLAIRs team

Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 260128B (GCN 43561). 

The burst that triggered ECLAIRs consists of a single peak lasting around 10 s in the 4-50 keV energy band.

The time-averaged spectrum from T0-9.24 s to T0-0.24 s (T0 = 2026-01-28T06:48:34.72 UT) in the energy range 4-50 keV is not well fitted by a simple powerlaw model. This indicates some spectral curvature. Using a blackbody with a temperature kT = (2.29 +0.22/-0.20) keV provides a good fit. With this model, the fluence in the energy range 4-120 keV is  (1.04 +0.05/-0.30) e-7 erg/cm². 

Using either a broken power law or a power law with an exponential cutoff provides acceptable fits. However, given the faintness of the event, the model parameters remain poorly constrained. 

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)