TITLE: GCN CIRCULAR NUMBER: 18168 SUBJECT: GRB 150819A: Swift/UVOT Upper Limits DATE: 15/08/19 10:22:34 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and T. N. Ukwatta (LANL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150819A 143 s after the BAT trigger (Ukwatta et al., GCN Circ. 18163). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 18167) 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 143 292 147 >21.0 u_FC 301 551 246 >20.2 white 143 7062 569 >21.4 v 631 6037 274 >19.6 b 557 6857 274 >20.3 u 301 6652 501 >20.4 w1 680 6447 274 >20.0 m2 656 6242 274 >19.9 w2 607 7135 346 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.22 in the direction of the burst (Schlegel et al. 1998).