GRB 231216A: Swift/UVOT Upper Limits

The Swift/UVOT began settled observations of the field of GRB 231216A 191 s after the BAT trigger (Sbarrato et al., GCN Circ. 35378). No optical afterglow consistent with the XRT position was 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 u_FC 191 441 246 >20.2 v 497 814 58 >18.5 b 447 1028 63 >20.0 u 191 1018 432 >20.8 w1 546 864 58 >19.5 m2 819 839 19 >18.3 w2 473 790 58 >19.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.082 in the direction of the burst (Schlegel et al. 1998).