TITLE: GCN CIRCULAR NUMBER: 41728 SUBJECT: GRB 250905A: Swift/UVOT Upper Limits DATE: 25/09/05 20:04:34 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk> S. R. Oates (Lancaster Uni.) and R. Brivio (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250905A 140 s after the BAT trigger (Brivio et al., GCN Circ. 41714). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 41722) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag/3sigUL white (FC) 140 290 147 >21.0 u (FC) 300 405 103 >19.8 v 4973 16058 1082 >20.3 b 5794 5978 181 >20.3 u 5588 27905 1036 >21.1 uvw1 5383 27038 1082 >20.4 uvm2 5178 16867 989 >20.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.054 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41728. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...