TITLE: GCN CIRCULAR NUMBER: 12606 SUBJECT: GRB 111129A: Swift/UVOT Detection DATE: 11/11/30 10:47:24 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (MSSL-UCL) and J. L. Racusin (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 111129A 96 s after the BAT trigger (Racusin et al., GCN Circ. 12600). A source consistent with the XRT position (Osborne et al., GCN Circ. 12601) is detected in the initial UVOT exposures in the white and u filters. The source had already faded by the time the other filters were used. The preliminary UVOT position is: RA (J2000) = 20:29:44.15 = 307.43396 (deg.) Dec (J2000) = -52:42:46.5 = -52.71293 (deg.) with an estimated uncertainty of 0.54 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 96 245 147 19.11 ± 0.1 white 534 726 39 >20.32 v 584 12305 524 >19.9 b 509 16631 1223 >21.3 u 254 503 246 19.10 ± 0.16 w1 633 22753 1296 >21.2 m2 608 6008 413 >20.4 w2 559 12186 1120 >21.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).