TITLE: GCN CIRCULAR NUMBER: 24731 SUBJECT: GRB 190531B: Swift/UVOT Upper Limits DATE: 19/06/03 19:12:44 GMT FROM: Kira Simpson at PSU GRB 190531B: Swift/UVOT Upper Limits K. K. Simpson (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 190531B 18175 s after the LAT trigger (Axelsson et al., GCN Circ. 24701). No optical afterglow consistent with the XRT position (D'Avanzo et al., GCN Circ. 24706) 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 initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag b 18661 24137 365 >20.5 u 18497 29702 551 >21.1 w1 18175 29509 1132 >20.7 m2 19630 25766 972 >20.9 w2 18826 24990 1459 >21.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).