TITLE: GCN CIRCULAR NUMBER: 20441 SUBJECT: GRB 170111A: Swift/UVOT Upper Limits DATE: 17/01/12 14:21:19 GMT FROM: Mike Siegel at PSU/Swift MOC M.H. Siegel (PSU) and A. P. Beardmore (U Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170111A 111 s after the BAT trigger (Beardmore et al., GCN Circ. 20423). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 20424) 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 111 261 147 >20.6 white 111 570 167 >20.7 v 601 621 19 >18.0 b 525 545 19 >19.6 u 676 696 19 >19.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).