TITLE: GCN CIRCULAR NUMBER: 43910 SUBJECT: GRB 260228A: SVOM/ECLAIRs refined analysis DATE: 26/03/03 15:29:58 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> M. G. Bernardini (INAF-OAB, LUPM), M. Brunet, J.-L. Atteia, O. Godet (IRAP), W. J. Xie (NAOC), Y. Julakanti, R. A. J. Eyles-Ferries (Leicester Univ.) 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 ECLAIRs observations of GRB 260228A (SVOM burst-id 26022802). The burst that triggered ECLAIRs onboard (GCN 43882) consists of a double-peaked pulse with a duration of T90 = (18.3 -4.0/+16.0) s in the 4-120 keV energy band. Since the GRB is observed mainly below 20 keV, we also computed the duration in the 4-20 keV energy band: T90 = (22.9 -4.2/+9.4) s. The time-averaged spectrum from T0+7 s to T0+31 s (T0 = 2026-02-28T20:55:34.620) in the energy range 5-120 keV is best fitted by a broken power-law model with alpha_1 = (-1.33 -0.43/+0.34), alpha_2 = (-2.83 -0.33/+0.37) and E_break = (9.6 -0.9/+1.2) keV. With this model, the total 4-120 keV fluence is (4.27 -2.6/+0.2)E-7 erg/cm^2. All the quoted errors are at the 68% confidence level. With these parameters, the Eiso ranges from 1.6E49 erg assuming z=0.1 to 8.6E52 erg at z=10. The location of GRB 260228A in the Amati plane for different redshifts is available here: https://drive.google.com/file/d/1FfPqOo6kSt6L5QR-DGjUvxdrTwvSlPfT/view?usp=s... 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: Maria Grazia Bernardini (INAF-OAB, LUPM) (maria.bernardini at inaf.it) View this GCN Circular online at https://gcn.nasa.gov/circulars/43910. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...