TITLE: GCN CIRCULAR NUMBER: 10989 SUBJECT: GRB 100725A: Swift/UVOT Upper Limits DATE: 10/07/25 23:00:31 GMT FROM: Tyler Pritchard at PSU GRB 100725A: Swift/UVOT Upper Limits T. A. Pritchard (PSU) and C. B. Markwardt (CRESST/GSFC/UMD) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100725A 85 s after the BAT trigger (Markwardt et al., GCN Circ. 10979). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 10985) 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 85 234 147 >20.7 u_FC 297 547 246 >20.3 white 85 11646 1486 >21.8 v 626 13269 1202 >20.2 b 552 7488 440 >20.6 u 297 7353 736 >20.5 w1 675 7148 510 >20.4 m2 651 6942 510 >20.3 w2 602 12552 1396 >21.2 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998).