TITLE: GCN CIRCULAR NUMBER: 20191 SUBJECT: GRB 161117B: Swift/UVOT Upper Limits DATE: 16/11/17 23:07:40 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 161117B 84 s after the BAT trigger (Troja et al., GCN Circ. 20182). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 20186) 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 84 234 147 >21.1 u_FC 296 546 246 >20.3 white 84 1026 334 >21.4 v 626 820 39 >18.1 b 552 745 39 >19.6 u 296 720 265 >20.3 w1 676 870 39 >18.9 m2 651 844 39 >19.9 w2 602 1050 57 >19.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998).