TITLE: GCN CIRCULAR NUMBER: 13829 SUBJECT: GRB 120927A: Swift/UVOT Upper Limits DATE: 12/09/29 15:02:02 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (NASA/CRESST/GSFC) and A. Maselli (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 120927A 158 s after the BAT trigger (Maselli et al., GCN Circ. 13822). No optical afterglow consistent with the enhanced XRT position (Beardmore et al. GCN Circ. 13824) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 158 308 147 >20.3 u_FC 317 567 246 >19.5 white 158 6331 580 >21.0 v 648 6625 317 >19.1 b 572 6127 432 >20.1 u 317 5921 659 >20.2 w1 697 5717 413 >19.6 m2 672 5511 225 >19.6 w2 623 6537 432 >20.3 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).