TITLE: GCN CIRCULAR NUMBER: 43922 SUBJECT: GRB 260303A: SVOM/ECLAIRs refined analysis DATE: 26/03/05 09:11:45 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> M. Brunet, L. Bouchet (IRAP), Z. Wang, D. Kong(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 260303A (SVOM burst-id sb26030303 – GCN 43901, trigger time T0 = 2026-03-03T06:01:47 UTC). The burst that triggered ECLAIRs shows a single peak lightcurve. The burst duration is estimated to be around 14.5s (from T0-19.5s to T0-5s) in the 4-120 keV energy band through imaging. The refined burst localization is RA, Dec = 93.1458, 41.1727 degrees: RA (J2000) = 06h12m34.99s Dec (J2000) = 41d10m21.72s with a 90% C.L. radius of 9.6 arcmin (including systematic error of 6 arcmin added in quadrature). The time-averaged spectrum from T0-19.5 s to T0-5 s in the energy range 5-120 keV is best fitted by a powerlaw model with a photon index of 1.67 +0.14/-0.13. With this model, the 4-120 keV fluence is (1.19 +0.11/-0.20) e-6 erg/cm² and the 4-120 keV photon flux is 2.73 +0.16/-0.31 ph/cm²/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) View this GCN Circular online at https://gcn.nasa.gov/circulars/43922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...