TITLE: GCN CIRCULAR NUMBER: 23460 SUBJECT: GRB 181126A: Swift/UVOT Upper Limits DATE: 18/11/26 22:14:48 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and E. Sonbas (Adiyaman Univ.) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181126A 80s after the BAT trigger (Sonbas et al., GCN Circ. 23453). No optical afterglow consistent with the XRT position (Beardmore et al., GCN Circ. 23455) 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 80 230 147 >20.4 white 80 1181 342 >20.5 v 622 1069 58 >18.0 b 1147 1167 20 >18.2 u 292 1142 285 >20.1 w1 671 1118 58 >20.2 m2 646 1093 58 >19.0 w2 597 1044 58 >18.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst (Schlegel et al. 1998).