GCN Circular 17785
M. M. Chester (PSU) and K. L. Page (U Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150428A 179 s after the BAT trigger (Page et al., GCN Circ. 17765). No optical afterglow consistent with the enhanced XRT position (Osborne et al. GCN Circ. 17768) 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 one subsequent exposure are: Filter T_start(s) T_stop(s) Exp(s) UL (3-sigma) white_FC 179 329 147 >20.9 u 3572 3726 152 >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).