TITLE: GCN CIRCULAR NUMBER: 29213 SUBJECT: GRB 201229A: Swift/UVOT Detection DATE: 21/01/01 02:06:07 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 201229A 117 s after the BAT trigger (Sbarufatti et al., GCN Circ. 29192). A source consistent with the XRT position (Osborne et al. GCN Circ. 29193) is detected in the initial UVOT exposures, consistent with the optical transient reported in the initial circular and confirmed by SAO (Moskvitin et al., GCN Circ. 29203) and AbAO (Pankov et al., GCN Circ. 29205). The preliminary UVOT position is: RA (J2000) = 14:02:45.40 = 210.68916 (deg.) Dec (J2000) = +48:11:53.3 = 48.19814 (deg.) with an estimated uncertainty of 0.44 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 (fc) 117 266 147 18.22 +/- 0.05 white 555 749 38 18.50+/-0.13 white 879 1029 147 19.17+/-0.13 white 1182 1548 58 19.42+/-0.34 white 23280 24102 801 20.88+/-0.22 v 605 1597 116 >18.48 v 17146 34853 1217 >20.39 b 531 1523 97 >19.33 b 22367 23274 885 >21.24 u (fc) 275 525 245 18.13+/-0.09 u 680 5086 107 18.57+/-0.25 u 12362 29756 1220 20.54+/-0.34 uvw1 654 5071 254 19.04+/-0.25 uvw1 28021 28921 885 >20.45 uvw2 16239 34408 1771 20.27+/-0.21 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).