TITLE: GCN CIRCULAR NUMBER: 42209 SUBJECT: GRB 251011B: Swift/UVOT Upper Limits DATE: 25/10/12 15:56:51 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18@psu.edu> M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251011B 107 s after the BAT trigger (D'Ai et al., GCN Circ. 42197). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 42201) 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 107 257 147 >20.9 white 107 257 147 >20.9 u 320 463 141 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.017 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42209. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...