TITLE: GCN CIRCULAR NUMBER: 29303 SUBJECT: GRB 210112A: Swift/UVOT Detection DATE: 21/01/15 03:50:43 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and Ambrosi (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210112A 83 s after the BAT trigger (Ambrosi et al., GCN Circ. 29289). A source consistent with the XRT position (Goad et al. GCN Circ. 29290) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 14:36:01.49 = 219.00619 (deg.) Dec (J2000) = +33:03:15.3 = 33.05424 (deg.) with an estimated uncertainty of 0.50 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 83 233 147 19.54 +/- 0.10 v 626 1419 97 >18.5 b 551 1517 97 >19.1 u 296 1493 304 >20.2 w1 675 1468 78 >19.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.014 in the direction of the burst (Schlegel et al. 1998).