TITLE: GCN CIRCULAR NUMBER: 23982 SUBJECT: GRB 190320A: Swift/UVOT Upper Limits DATE: 19/03/20 16:22:03 GMT FROM: Frank Marshall at Swift/UVOT F. E. Marshall (NASA/GSFC) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 190320A 2834 s after the BAT trigger (Gropp et al., GCN Circ. 23973). No optical afterglow consistent with the XRT position (Lipunov et al. GCN Circ. 23976) 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 2834 2984 147 >20.0 white 2834 16112 1213 >21.4 v 2992 21862 1645 >20.4 b 3812 15216 1082 >20.8 u 3607 3807 197 >19.6 w1 3402 3602 197 >19.5 m2 3196 22200 524 >19.8 w2 4223 20949 1776 >20.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.23 in the direction of the burst (Schlegel et al. 1998).