TITLE: GCN CIRCULAR NUMBER: 43940 SUBJECT: GRB 260307B: SVOM detection of a burst DATE: 26/03/07 14:09:39 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> F. Magnani, A. Foisseau (CPPM), M. Brunet, O. Godet (IRAP), report on behalf of the SVOM mission team: At 2026-03-07T13:45:26 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260307B (SVOM burst-id sb26030704). 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 4 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.92 in the [8-120] keV energy band over a time window of 40.96 seconds starting at 2026-03-07T13:45:06. The localization of the best alert is R.A., Dec. 155.5760, -21.0620 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.01 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-03-07T13:48:16 UTC, 170 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 155.5216, -20.9972 degrees: R.A. (J2000) = 10h22m05.19s Dec. (J2000) = -20d59m49.81s with a 90% C.L. radius of 43.83 arcseconds. This location is 4.94 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. No optical observation could be performed by SVOM/VT for the time being. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Francesco Magnani: magnani@cppm.in2p3.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43940. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...