TITLE: GCN CIRCULAR NUMBER: 41681 SUBJECT: Subject GRB 250903A: SVOM/MXT afterglow detection DATE: 25/09/03 19:02:33 GMT FROM: Diego Gotz at CEA <diego.gotz@cea.fr> D. Götz (CEA), M. Moita (CEA) F. Robinet (IJCLab), P. Maggi (ObAS), H. Goto (Kanazawa Univ./CEA), C. Plasse (CEA) , C. Van Hove (IJCLab) report of behalf of the SVOM/MXT Team: GRB 250903A (Maiolino et al. GCN# 41677) was observed by SVOM/MXT after an automatic SVOM slew, but due to Earth constraints the observation started at 2025-09-03T18:30:41, about 66 minutes after Tb. Using the on board automatic detection software, MXT detects a faint source at the coordinates R.A. (J2000) = 23h47m21s Dec (J2000) = -75d58m43s with a 90% C.L. radius of 3 arc min (including 25 arc sec systematic error added in quadrature). This position is at 3.1 arc min from the ECLAIRs position and 0.5 arc min from the optical counterpart reported by An et al. (GCN# 41679). We hence identify this source as the X-ray afterglow of GRB 250903A. Further analysis will be perfromed once the full X-band data set is received. 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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. The SVOM point of contact for this burst is Tais Maiolino: tais.maiolino@lupm.in2p3.fr. 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/41681. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...