TITLE: GCN CIRCULAR NUMBER: 17882 SUBJECT: GRB 150527A: Swift/UVOT Upper Limits DATE: 15/05/27 21:46:10 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150527A 68 s after the BAT trigger (Evans et al., GCN Circ. 17874). No optical afterglow consistent with the enhanced XRT position (Evans et al. GCN Circ. 17879) or with the RATIR or REM sources (Butler et al., GCN Circ. 17876 and Nicastro et al., GCN Circ. 17881) 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 68 218 147 >20.2 u_FC 280 523 240 >19.1 white 10385 11927 1542 >21.2 v 4315 4515 197 >18.8 b 3700 10380 1082 >20.8 u 280 6271 623 >19.6 w1 5920 6120 197 >19.4 w2 4110 12019 281 >19.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.97 in the direction of the burst (Schlegel et al. 1998). We note however that the value for extinction could be unreliable at this position.