TITLE: GCN CIRCULAR NUMBER: 41720 SUBJECT: GRB 250903A: Swift/UVOT detection DATE: 25/09/05 09:51:33 GMT FROM: s.shilling@lancaster.ac.uk S. P. R. Shilling (Lancaster U.) reports on behalf of the Swift/UVOT team: Swift/UVOT has performed follow-up observations of the SVOM/ECLAIRs-detected source GRB 250903A. Swift/UVOT observed the field of GRB 250903A (Maiolino et al., GCN 41677) for 2.3 ks in the U-band starting at 20:57:46 UT, 3.5 hours after the detection by SVOM/ECLAIRs. A source consistent with the TRT optical counterpart position (An et al., GCN 41679), within the SVOM/ECLAIRs error circle, is detected and is fading. The preliminary detection magnitude reported below is calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). Filter T_start(s) T_stop(s) Exp(s) Mag u 12770 24862 2330 19.71 +/- 0.11 View this GCN Circular online at https://gcn.nasa.gov/circulars/41720. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...