TITLE: GCN CIRCULAR NUMBER: 8511 SUBJECT: GRB 081109B: Swift/UVOT refined analysis DATE: 08/11/10 11:20:01 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (MSSL/UCL) and S. Immler (CRESST/GSFC/UMD) report on behalf of the Swift UVOT team. The Swift UltraViolet/Optical Telescope (UVOT) began observing GRB 081109B (Swift BAT trigger number 334129; Immler et al., GCN Circ. 8502) on November 9, 2008, at 13:50:24 UT, 187 seconds after the trigger. No new source is detected in any of our images or summed images which cover the BAT error circle descibed in GCN Circ. 8502. The 5-sigma upper limits in the summed images for GRB081109B at a random background position within the BAT error circle are given below: Filter Tstart(s) Tstop(s) Exp(s) Magnitude wh 187 5946 560 >20.78 (5-sigma UL) u 393 12195 533 >20.1 (5-sigma UL) b 418 5741 235 >19.9 (5-sigma UL) uvw2 468 6152 413 >19.8 (5-sigma UL) v 492 6357 413 >19.3 (5-sigma UL) uvm2 344 10975 1142 >20.2 (5-sigma UL) uvw1 369 11882 1121 >20.5 (5-sigma UL) The values quoted above are on the UVOT Photometric System (Poole et al, 2008, MNRAS 383, 627). They are not corrected for the expected galactic reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).