TITLE: GCN CIRCULAR NUMBER: 39363 SUBJECT: SVOM/sb25021804: SVOM detection of a long X-ray transient DATE: 25/02/18 15:56:15 GMT FROM: Stéphane Schanne at CEA Paris-Saclay/IRFU <s.schanne@cea.fr> C.-W. Wang, W.-J. Tan (IHEP), D. Turpin, S. Schanne, N. Dagoneau (CEA) report on behalf of the SVOM mission team: The SVOM/ECLAIRs telescope triggered and located a long duration soft X-ray transient (SVOM burst-id sb25021804) starting at 2025-02-18T07:20:27 UTC (Tb). The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. The burst was detected by the Image Trigger (IMT) and only 1 alert was produced with a signal-to-noise ratio of 7.56 in the 5-8 keV energy band over a time window of 22 minutes starting at Tb. The sub-image transmitted shows a clean point-like source. The localization of the alert is R.A., Dec = 195.020, 28.078 degrees: RA (J2000) = 13h00m04.93s Dec (J2000) = 28d04m39.02s with a 90% C.L. radius of 10.4 arcmin (including systematic error of 2 arcmin added in quadrature). We notice that this error-box contains several X-ray sources which could produce such a transient, including 4 AGNs and the ULX-candidate labelled "[SRW2012] Src. 6" in Simbad, located at 9.2 arcmin distance. This trigger did not reach the slew threshold, hence no automatic slew was performed. A SVOM ToO has been scheduled and a Swift XRT ToO has been requested. The Space 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 Chen-Wei Wang (IHEP) : cwwang@ihep.ac.cn 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/39363. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...