TITLE: GCN CIRCULAR NUMBER: 40358 SUBJECT: GRB 250506A: SVOM detection of a burst DATE: 25/05/06 03:20:58 GMT FROM: SVOM_group Chenwei WANG (IHEP), Lin LAN, Wenjin XIE, Donghua ZHAO (NAOC), Li ZHANG (IHEP), Pierre MAGGI (ObAS) on behalf of the SVOM mission team. SVOM/ECLAIRs trigger on the gamma-ray burst GRB 250506A (SVOM burst-id sb25050601) starting at 2025-05-06T02:23:22 UTC (Tb). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Count-Rate Trigger (CRT), which produced a sequence of 1 alert. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 12.51 in the [8-120] keV energy band over a time window of 2.50 seconds starting at Tb. The localization of the best alert is R.A., Dec. 219.61, 29.28 degrees: R.A. (J2000) = 14h38m27.02s Dec. (J2000) = 29d16m38.09s with a 90% confidence level (C.L.) radius of 6.47 arcmin (including systematic error of 2 arcmin added in quadrature). This burst also triggered SVOM/GRM with 3 GRDs but only the first pulse is detected, since the other part is in occultation. The lightcurve of GRM could be found in the link below: https://www.bursthub.cn//admin/static/svgrb250506A.png SVOM slewed to the burst. It was occulted by the Earth after slew, thus neither MXT nor VT data are available for the early time. 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 Chenwei Wang: cwwang@ihep.ac.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.