TITLE: GCN CIRCULAR NUMBER: 22464 SUBJECT: GRB 180305A: Swift/UVOT Upper Limits DATE: 18/03/06 18:03:54 GMT FROM: Sam Emery at MSSL-UCL S.W.K. Emery (MSSL-UCL) and M. H. Siegel (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180305A 30621 s after the Fermi/LAT trigger (Axelsson et al., GCN Circ. 22457). No optical afterglow consistent with the enhanced XRT position (D'Avanzo et al., GCN Circ. 22462) or the RATIR and Mondy detections (Troja et al., GCN Circ. 22460; Mazaeva et al., GCN Circ. 22463) 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) in the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 30808 52964 961 >21.4 u 30621 52533 2623 >20.7 v 30994 48392 712 >19.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.454 in the direction of the burst (Schlegel et al. 1998).