TITLE: GCN CIRCULAR NUMBER: 27351 SUBJECT: GRB 200306A: Swift/UVOT Upper Limits DATE: 20/03/08 22:55:27 GMT FROM: Sam LaPorte at PSU GRB 200306A: Swift/UVOT Upper Limits J. D. Gropp (PSU) and K. K. Simpson (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200306A 85 s after the BAT trigger (Simpson et al., GCN Circ. 27320). No optical afterglow consistent with the optical position (Strausbaugh et al., GCN Circ. 27321) 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 85 235 147 >21.0 white 85 6191 459 >20.7 v 5049 11928 1011 >20.1 b 4434 16845 1278 >20.5 u 297 5864 351 >20.1 w1 5459 5659 197 >19.7 m2 5254 5454 197 >19.1 w2 4844 11087 1082 >20.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998).