TITLE: GCN CIRCULAR NUMBER: 20554 SUBJECT: GRB 170127B: Swift/UVOT Upper Limits DATE: 17/01/28 02:36:04 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170127B 114 s after the BAT trigger (Cannizzo et al., GCN Circ. 20540). No optical afterglow consistent with the enhanced XRT position (Goad et al. GCN Circ. 20550) 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) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 114 264 147 >21.2 u_FC 327 576 246 >19.9 white 114 1377 373 >21.0 v 656 1427 97 >19.4 u 327 576 246 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).