TITLE: GCN CIRCULAR NUMBER: 23303 SUBJECT: GRB 181003A: Swift/UVOT Upper Limits DATE: 18/10/03 17:47:56 GMT FROM: Sam LaPorte at PSU GRB 181003A: Swift/UVOT Upper Limits S. J. LaPorte (PSU) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181003A 3095 s after the BAT trigger (Beardmore et al., GCN Circ. 23295). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 23296) 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 5040 5240 196 >20.83 uvm2 3452 3652 196 >19.46 u 3862 3902 39 >19.19 v 3427 3447 196 >19.79 uvw1 3658 3857 196 >19.85 uvw2 5451 5597 144 >19.37 white 3091 3240 294 >21.73 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).