GCN Circular 26690
GRB 200109A: Swift/UVOT Upper Limits K. K. Simpson (PSU) and A. Melandri (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200109A 110 s after the BAT trigger (Melandri et al., GCN Circ. 26678). No optical afterglow consistent with the XRT position (Melandri et al. GCN Circ. 26678) 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 110 259 147 >20.5 u_FC 268 518 246 >19.0 white 110 1023 295 >20.9 u 268 518 246 >19.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.29 in the direction of the burst (Schlegel et al. 1998).