TITLE: GCN CIRCULAR NUMBER: 10157 SUBJECT: GRB 091109B: Swift/UVOT Upper Limits DATE: 09/11/10 12:35:35 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 091109B 84s after the BAT trigger (Oates et al., GCN 10148). We do not detect any source at the enhanced Swift XRT position (Evans et al. GCN 10151) and at the location of source A detected by the VLT (Levan et al. GCN 10154, Malesani et al. GCN 10156) The 3-sigma upper limits for the finding chart exposures (FC) and summed images are: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- white (FC) 84 234 147 > 21.25 u (FC) 296 546 246 > 20.29 white 577 18629 1313 > 22.09 v 627 11274 1172 > 20.96 b 553 17890 1337 > 21.78 u 701 23171 1761 > 21.61 uvw1 677 22710 1988 > 21.44 uvm2 652 12179 1160 > 20.87 uvw2 603 7050 471 > 20.52 ------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.17 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).