TITLE: GCN CIRCULAR NUMBER: 18615 SUBJECT: GRB 151118A: Swift/UVOT Upper Limits DATE: 15/11/18 12:31:35 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and Amaral-Rogers (U Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151118A 70 s after the BAT trigger (Amaral-Rogers et al., GCN Circ. 18611). No optical afterglow consistent with the XRT position (Amaral-Rogers et al. GCN Circ. 18611) 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) 70 220 148 >20.6 u (fc) 282 532 246 >20.0 white 70 754 186 >20.8 v 612 631 19 >18.3 b 537 730 39 >19.3 u 282 705 265 >19.9 w1 661 680 19 >18.2 w2 587 607 19 >17.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.10 in the direction of the burst (Schlegel et al. 1998).