TITLE: GCN CIRCULAR NUMBER: 40026 SUBJECT: GRB 250403A : SVOM detection of a burst DATE: 25/04/03 15:58:17 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> Y. Julakanti, R. A. J. Eyles-Ferris (U. Leicester), S. Schanne, D. Turpin (CEA), M. Brunet (IRAP) report: SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250403A (SVOM burst-id sb25040305) starting at 2025-04-03T15:15:20 UTC (Tb), also detected by Fermi (GCN 40025). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT) which produced a sequence of 19 alerts. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 42.11 in the 8-120 keV energy band over a time window of 20.40 seconds starting at Tb. The downloaded light curve shows a single broad structure of duration of about 20 seconds. The localization of the best alert is R.A., Dec 194.5927, -24.3762 degrees: RA (J2000) = 12h58m22.24s Dec (J2000) = -24d22m34.36s with a 90% C.L. radius of 2.71 arcmin (including systematic error of 2 arcmin added in quadrature). The burst was also detected by GRM as SVOM burst-id sb25040306. No immediate slew was performed on this burst. A SVOM ToO has been programmed for follow-up. 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. The Burst Advocate (BA) on shift for this burst is Y. Julakanti (skyj1@leicester.ac.uk). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40026. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...