TITLE: GCN CIRCULAR NUMBER: 29485 SUBJECT: GRB 210211A: Swift/UVOT Detection DATE: 21/02/11 22:59:12 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210211A 78 s after the BAT trigger (Troja et al., GCN Circ. 29472). A source consistent with the XRT position (Osborne et al. GCN Circ. 29478) and the REM detection (d'Avanzo et al., GCN Circ. 29474)is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 17:57:45.68 = 269.44035 (deg.) Dec (J2000) = -46:16:01.6 = -46.26711 (deg.) with an estimated uncertainty of 0.47 arc sec. (radius, 90% confidence). 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 78 227 147 17.89 +/- 0.06 white 596 611 15 >18.6 white 5391 5587 197 >20.3 v 4239 4438 197 >19.8 b 545 565 19 >18.4 u 290 489 196 >18.6 m2 4444 4491 47 >18.3 w2 4034 4234 197 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.127 in the direction of the burst (Schlegel et al. 1998).