TITLE: GCN CIRCULAR NUMBER: 30857 SUBJECT: GRB 210919A: Swift/UVOT Upper Limits DATE: 21/09/21 02:35:14 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18@psu.edu> M. H. Siegel (PSU) and A. Tohuvavohu (U. Toronto) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210919A 100 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 30846). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 30850) 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 100 249 147 >20.8 u_FC 312 561 246 >19.9 white 100 1193 343 >21.4 v 643 1244 70 >18.7 b 568 1342 63 >19.3 u 312 1318 304 >19.8 w1 693 1293 58 >19.7 m2 1248 1268 19 >19.0 w2 618 1044 39 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.141 in the direction of the burst (Schlegel et al. 1998).