TITLE: GCN CIRCULAR NUMBER: 10807 SUBJECT: GRB 100526A: Swift/UVOT Upper Limits DATE: 10/05/27 18:23:49 GMT FROM: Tyler Pritchard at PSU T. A. Pritchard (PSU) and Vetere (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100526A 151 s after the BAT trigger (Vetere et al., GCN Circ. 10797). No optical afterglow consistent with the enhanced XRT position (A. P. Beardmore et al.,GCN Circ. 10800) 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) 151 301 147 >21.1 u (FC) 310 559 246 >20.1 white 151 7321 783 >22.4 v 640 6296 313 >20.3 b 565 7116 491 >21.5 u 310 6911 717 >21.3 w1 690 6706 471 >20.9 m2 4865 6501 393 >20.6 w2 791 7374 263 >20.6 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)