GCN Circular 21722
F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170827A 134 s after the BAT trigger (Marshall et al., GCN Circ. 21718). No optical afterglow consistent with the XRT position (Marshall et al. GCN Circ. 21718) 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 a subsequent short exposure are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 134 284 147 >19.8 u 292 298 6 >17.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.11 in the direction of the burst (Schlegel et al. 1998).