TITLE: GCN CIRCULAR NUMBER: 42670 SUBJECT: GRB 251111A: SVOM/ECLAIRs refined analysis DATE: 25/11/13 15:34:26 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> H. Yang, M. Brunet, O. Godet (IRAP), W.-J. Xie (NAOC), S. Schanne, B. Hubert (CEA), Y.-H. Cheng (SWIFAR,YNU), B.-T. Wang (YNAO) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 251111A (SVOM burst-id sb25111101, GCN 42637) detected at T0 = 2025-11-11T05:10:18.26. The burst that triggered ECLAIRs consists of a single peak mostly seen in the 4-30 keV, with a duration of T90 = 5.31 (-0.68 / +2.36) s in the 4-20 keV energy band. The time-averaged spectrum from the peak (T0-5.3 s to T0+5 s) in the 5-30 keV energy range is well fitted by a power-law model with a photon index of 2.4 +/-0.2.The large photon index suggests that the peak energy is below 4 keV, indicating that this event is an X-ray flash. A blackbody model is also tested but does not provide a good fit. With the power-law model, the total 4-120 keV fluence is (1.5+/-0.2)e-07 erg/cm^2. 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: Hui Yang (IRAP) (hui.yang@irap.omp.eu). View this GCN Circular online at https://gcn.nasa.gov/circulars/42670. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...