GRB 240811A: Swift/UVOT Upper Limits

The Swift/UVOT began settled observations of the field of GRB 240811A 102 s after the BAT trigger (Page et al., GCN Circ. 37136). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 37141) 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 102 252 147 >21.0 u_FC 315 564 246 >20.7 white 102 1191 353 >21.9 v 644 5026 255 >18.7 b 570 1167 58 >20.0 u 315 1142 285 >20.7 w1 1098 5251 34 >19.2 m2 5031 5231 197 >18.8 w2 4622 4821 197 >19.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998).