TITLE: GCN CIRCULAR NUMBER: 22064 SUBJECT: GRB 171027A: Swift/UVOT Upper Limits DATE: 17/10/28 10:59:30 GMT FROM: Samantha Oates at MSSL S. R. Oates (U. Warwick) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 171027A 96 s after the BAT trigger (D'Avanzo et al., GCN Circ. 22053). No optical afterglow consistent with the optical position (Watson et al. GCN Circ. 22057) 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 96 246 147 >20.6 u_FC 308 558 246 >20.0 white 96 6148 428 >21.2 v 639 6558 432 >19.7 b 564 5943 236 >20.3 u 308 5737 462 >20.3 w1 688 6835 282 >19.8 m2 5126 6763 393 >19.8 w2 4716 6354 393 >20.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.14 in the direction of the burst (Schlegel et al. 1998).