TITLE: GCN CIRCULAR NUMBER: 33709 SUBJECT: GRB 230216A: Swift/UVOT Upper Limits DATE: 23/04/28 17:55:29 GMT FROM: noelklingler@gmail.com

N. Klingler (GSFC/UMBC/CRESTII) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230216A 106 s after the BAT trigger (Klingler et al., GCN Circ. 33328). No optical afterglow consistent with the optical position (Gendre et al. GCN Circ. 33329) is detected in the initial UVOT exposures. 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 106 256 147 >16.9 u_FC 264 514 246 >16.9 white 106 1188 353 >16.8 v 594 1065 58 >15.9 b 520 1164 58 >16.5 u 264 1139 304 >16.9 w1 643 1114 58 >17.1 m2 618 1090 58 >17.6 w2 569 1213 78 >17.7

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.198 in the direction of the burst (Schlegel et al. 1998).