TITLE: GCN CIRCULAR NUMBER: 10808 SUBJECT: GRB 100526B: Swift/UVOT Upper Limits DATE: 10/05/27 18:26:17 GMT FROM: Tyler Pritchard at PSU T. A. Pritchard (PSU) and Siegel (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100526B 3288 s after the BAT trigger (Siegel et al., GCN Circ. 10799). No optical afterglow consistent with the XRT position (Kennea et al., GCN Circ. 10802) 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) 3288 3438 147 >21.3 white 3288 4669 344 >21.7 v 3445 5080 393 >20.2 b 4265 5880 372 >20.7 u 4060 5695 393 >20.5 w1 3855 5491 393 >20.7 m2 3650 3849 197 >19.9 w2 4675 4875 197 >20.3 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).