TITLE: GCN CIRCULAR NUMBER: 44543 SUBJECT: GRB 260511B: SVOM detection of a burst DATE: 26/05/11 11:25:44 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> O. Godet, M. Brunet (IRAP), L. Zhang (IHEP), D. Kong (GXU) report on behalf of the SVOM mission team: At 2026-05-11T11:00:32 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260511B (SVOM burst-id sb26051102). This transient was also detected by Fermi/GM (GCN Circular 44542). 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 15 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 45.21 in the [8-120] keV energy band over a time window of 5.10 seconds starting at 2026-05-11T11:01:00. The localization of the best alert is R.A., Dec. 192.606, 4.094 degrees: R.A. (J2000) = 12h50m25.47s Dec. (J2000) = 4d05m40.00s with a 90% confidence level (C.L.) radius of 2.63 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a multiple peak structure with a T90 duration of about 41.2 -0.6/+1.0 (5-120 keV). This burst also triggered SVOM/GRM at 2026-05-11T11:00:31 on a timescale of 0.10 seconds with an SNR of 7. The SVOM/GRM light curve showed a multiple peak structure with a T90 duration of about 54.2 -5.2/+5.1 s (8-1100 keV). SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-05-11T11:03:32 UTC, 180 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 192.5735, 4.0405 degrees: R.A. (J2000) = 12h50m17.65s Dec. (J2000) = 4d02m25.68s with a 90% C.L. radius of 32.02 arcseconds. This location is 3.78 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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 zhangli: zhangli at ihep.ac.cn Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44543. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...