TITLE: GCN CIRCULAR NUMBER: 44486 SUBJECT: GRB 260504B: SVOM/ECLAIRs refined analysis DATE: 26/05/06 16:54:33 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> F. Piron (LUPM), M. Brunet (IRAP), N. Dagoneau (CEA), Y. Wang (PMO,CAS; UCB), W. J. Xie (NAO,CAS), 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 260504B (SVOM burst-id sb26050402 – GCN 44454, trigger time T0 = 2026-05-04T09:31:19 UTC), which was also detected by SVOM/GRM (GCN 44470), GECAM-B (GCN 44473) and Konus-Wind (GCN 44474). The burst that triggered ECLAIRs onboard shows a single peak lightcurve. The burst duration is T90 = 0.46 -0.06/+0.09 s in the 4-120 keV energy band. The time-averaged spectrum from T0+0.40 s to T0+0.86 s in the energy range 5-120 keV is best fitted by a powerlaw model with best-fit parameters: alpha = -0.72 +/-0.06. With this model, the 4-120 keV fluence is (1.87 ± 0.09) e-7 erg/cm^2 and the 4-120 keV photon flux is 6.0 ± 0.3 ph/cm²/s. We note that the photon index is consistent with the one found by SVOM/GRM (GCN 44470). 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: Frédéric Piron (LUPM) (piron at in2p3.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/44486. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...