TITLE: GCN CIRCULAR NUMBER: 30710 SUBJECT: GRB 210822A: Swift/UVOT Detection DATE: 21/08/25 06:21:36 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210822A 85 s after the BAT trigger (Page et al., GCN Circ. 30677). A fading source consistent with the XRT position (Page et al. GCN Circ. 30677) and the previously reported UVOT source is is detected in the initial UVOT exposures. Preliminary detections and 3-sigma upper limits 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 (fc) 86 236 147 13.63+/-1.10 white 577 1200 205 15.35+/-0.02 white 4965 5058 91 17.43+/-0.05 white 34405 35230 804 19.15+/-0.05 white 149533 190336 1894 20.64+/-0.11 v 627 1250 77 15.07+/-0.05 v 27494 28215 702 18.68+/-0.13 b 553 1176 58 15.31+/-0.04 b 4760 4960 196 17.56+/-0.06 b 33493 34400 885 19.18+/-0.08 u (fc) 298 548 245 13.78+/-0.03 u 700 1304 39 14.86+/-0.05 u 4555 4755 196 16.85+/-0.05 u 57947 58635 670 19.73+/-0.19 uvw1 676 1299 77 15.28+/-0.07 uvw1 39434 96567 1775 19.90+/-0.22 uvm2 824 1274 38 >17.66 uvm2 92215 93015 788 >20.06 uvw2 602 1225 77 17.21+/-0.18 uvw2 21659 64335 1469 20.40+/-0.34 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.162 in the direction of the burst (Schlegel et al. 1998).