TITLE: GCN CIRCULAR NUMBER: 10134 SUBJECT: GRB 091104: Swift/UVOT Upper Limits DATE: 09/11/04 17:13:20 GMT FROM: Peter Curran at MSSL P.A. Curran (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 091104 139s after the BAT trigger (Curran et al., GCN 10130). No optical afterglow consistent with the enhanched XRT position (Osborne et al., GCN 10131) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the finding charts (FC) and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag ------------------------------------------------------- white 139 289 147 >20.56 (FC) u 297 547 246 >19.69 (FC) white 139 993 301 >20.84 v 628 6155 87 >18.53 b 553 746 39 >18.88 u 297 721 265 >19.74 w1 677 870 39 >18.45 m2 652 845 39 >18.26 w2 776 4636 151 >19.71 The values quoted above 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).