TITLE: GCN CIRCULAR NUMBER: 25795 SUBJECT: GRB 190919B: Swift/UVOT Upper Limits DATE: 19/09/20 20:58:25 GMT FROM: Frank Marshall at Swift/UVOT F. E. Marshall (NASA/GSFC) and A. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 190919B 28564 s after the INTEGRAL trigger (Mereghetti et al., GCN Circ. 25788). No optical afterglow consistent with the optical position (Bolmer, GCN Circ. 25789; Tyurina et al. GCN Circ. 25791) 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 u_FC 28987 29196 206 >20.3 v 30258 36440 225 >19.6 b 29201 36022 301 >20.2 u 28987 35920 301 >20.7 w1 28564 35819 602 >20.8 m2 30471 30737 262 >20.3 w2 29416 36416 1204 >21.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).