TITLE: GCN CIRCULAR NUMBER: 44504 SUBJECT: GRB 260509A: SVOM detection of a burst DATE: 26/05/09 22:26:24 GMT FROM: Diego Gotz at CEA <diego.gotz@cea.fr> GRB 260509A: SVOM detection of a burst D. Götz (CEA/Irfu), A. Saccardi (CEA/Irfu), H. Goto (RIKEN), F. Lacreu (IAP), D. Adrien (CEA/Irfu), report on behalf of the SVOM mission team: At 2026-05-09T21:51:09 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260509A (SVOM burst-id sb26050905). 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 18 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 18.00 in the [5-20] keV energy band over a time window of 20.40 seconds starting at 2026-05-09T21:51:03. The localization of the best alert is R.A., Dec. 176.8870, 0.2095 degrees: R.A. (J2000) = 11h47m32.9s Dec. (J2000) = 0d12m34.2s with a 90% confidence level (C.L.) radius of 4.72 arcmin (including systematic error of 2 arcmin added in quadrature). We note the presence of a high proper motion star G 10-49 at a distance of 4.48 arcmin from the ECLAIRs position. The SVOM/ECLAIRs light curve showed a single peak structure with a T90 duration of about 14.7 +/-0.6 s. This burst was also detected by SVOM/GRM with a significance of 6.40. The SVOM/GRM light curve showed a double peak structure with a T90 duration of about 18 (-6/+10) s. SVOM slewed to the burst. MXT and VT began observing the field after the slew. The analysis of the data will be published in future circulars. 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 Dylan Adrien: dylan.adrien@cea.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44504. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...