TITLE: GCN CIRCULAR NUMBER: 21480 SUBJECT: GRB 170813A: Swift/UVOT Upper Limits DATE: 17/08/14 18:32:51 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) 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 170813A 144 s after the BAT trigger (Page et al., GCN Circ. 21468). No optical afterglow consistent with the enhanced XRT position (Osborne et al. GCN Circ. 21469) 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 144 293 147 >20.1 u_FC 302 551 246 >19.8 white 144 6769 727 >21.4 v 632 11867 1140 >19.3 b 557 6564 432 >20.7 u 302 6359 659 >20.4 w1 682 6154 413 >19.9 m2 4314 12580 1090 >20.5 w2 5339 10954 1145 >20.4