TITLE: GCN CIRCULAR NUMBER: 28482 SUBJECT: GRB 200922A: Swift/UVOT Detection DATE: 20/09/23 13:04:40 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and M. J. Moss (GWU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200922A 86 s after the BAT trigger (Moss et al., GCN Circ. 28471). We identify a fading source near the XRT position (Osborne et al. GCN Circ. 28473) and also at the location of a weak source in the DSS. The source position is: RA(J2000) = 19:47:48.76 = 296.95317 DEC(J2000) = -55:12:16.5 = -55.20457 Which is 3.0 arc-second from the enhanced XRT position. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 86 236 147 14.37+/-0.02 white 4770 4970 196 17.51+/-0.04 white 28889 28909 19 18.62+/-0.20 v 3745 3945 196 17.35+/-0.10 v 9268 23149 1460 17.79+/-0.05 b 4566 4765 196 17.95+/-0.07 b 27982 28889 881 18.49+/-0.05 u 4360 4560 196 17.18+/-0.06 u 15921 16791 848 18.20+/-0.06 uvw1 4156 4355 196 17.23+/-0.10 uvw1 11089 15915 887 18.26+/-0.09 uvw1 50455 56029 225 18.97+/-0.27 uvm2 3950 4150 196 17.12+/-0.12 uvm2 10182 11081 885 18.19+/-0.10 uvm2 50396 55850 223 19.26+/-0.36 uvw2 3541 5089 307 17.14+/-0.09 uvw2 21653 22553 885 18.77+/-0.12 uvw2 50338 55672 223 >19.44 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998).