TITLE: GCN CIRCULAR NUMBER: 40387 SUBJECT: GRB 250506A: Swift/UVOT Upper Limits DATE: 25/05/07 20:04:42 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk> S. R. Oates (Lancaster U.) and N. Klinger (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250506A 63 ks after the of the SVOM and Fermi-detected GRB 250506A (GCN Circs. 40355, 40358). No optical afterglow consistent with the SVOM MXT (Maggi et al., GCN Circ. 40364) and the XRT position (Burrows et al. GCN Circ. 40378) is detected in the initial UVOT exposures. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 64170 70154 1176 >22.1 v 64937 65102 163 >19.3 u 63403 69711 1530 >21.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40387. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...