TITLE: GCN CIRCULAR NUMBER: 42446 SUBJECT: GRB 251024A: Swift/UVOT Upper Limits DATE: 25/10/25 20:11:36 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18@psu.edu> M. H. Siegel and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251024A 132 s after the BAT trigger (Moss et al., GCN Circ. 42426). No optical afterglow consistent with the XRT position (Beardmore et al., GCN Circ. 42430) 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 white_FC 132 282 147 >21.0 u_FC 290 540 246 >19.9 white 132 591 167 >21.0 v 622 641 19 >18.0 b 547 567 20 >19.8 u 290 540 246 >19.9 w2 597 617 20 >19.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.044 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42446. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...