TITLE: GCN CIRCULAR NUMBER: 15545 SUBJECT: GRB 131128A: Swift/UVOT Detection DATE: 13/11/29 11:54:03 GMT FROM: Samantha Oates at MSSL S. R. Oates (UCL-MSSL) and E. Sonbas (NASA/GSFC/Adiyaman Univ.) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 131128A 91 s after the BAT trigger (Sonbas et al., GCN Circ. 15533). A source consistent with the optical position (Xu et al., GCN Circ. 15535) and the enhanced Swift-XRT position (Goad et al., GCN Circ 15538) is detected in the first UVOT white exposure only. A USNO-B1 catalogued star heavily contaminates the position of the optical candidate afterglow making the measurement very complicated. Preliminary detection 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) 91 241 147 19.11 +/- 0.11 white 583 1181 206 >21.44 u (FC) 303 552 245 >20.2 u 303 1130 285 >20.3 v 632 1231 78 >19.0 b 558 1155 58 >19.8 w1 683 1275 53 >18.9 m2 657 1255 78 >19.0 w2 608 1206 78 >19.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst