TITLE: GCN CIRCULAR NUMBER: 11787 SUBJECT: GRB 110312A: Swift/UVOT Upper Limits DATE: 11/03/13 13:26:40 GMT FROM: Samantha Oates at MSSL S. R Oates (UCL-MSSL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 110312A 168 s after the BAT trigger (Oates et al., GCN Circ. 11782). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 11784) 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 first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag ---------------------------------------------------------------- white_FC 168 318 147 >21.8 u_FC 327 577 246 >20.1 white 168 1896 429 >21.3 v 657 1946 156 >19.2 b 582 6063 315 >20.6 u 327 2020 382 >20.1 w1 706 1995 136 >19.6 m2 682 1970 156 >19.6 w2 1036 1402 39 >18.8 The values quoted above 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).