TITLE: GCN CIRCULAR NUMBER: 11298 SUBJECT: GRB100925A UVOT afterglow DATE: 10/09/25 12:23:06 GMT FROM: Phil Evans at U of Leicester F. E. Marshall (NASA/GSFC) reports on behalf of the Swift team: In response to GRB100925 (Swift/BAT trigger 434928), UVOT took a finding chart exposure of 150 seconds with the White filter starting 1882 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 16:59:01.68 = 254.75702 DEC(J2000) = -15:15:28.4 = -15.25789 with a 90%-confidence error radius of about 0.61 arc sec. This position is 11" from the center of the XRT error circle (Mangano et al. GCN Circ. 11296). The estimated magnitude is 16.83 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.61.