TITLE: GCN CIRCULAR NUMBER: 15266 SUBJECT: GRB 130925A: Swift/UVOT Upper Limits DATE: 13/09/27 11:37:03 GMT FROM: Stephen Holland at STScI S. T. Holland (STScI) and A. Y. Lien (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130925A 157 s after the BAT trigger (Lien et al. 2013, GCNC 15246). We do not detect any new source consistent with the GROND afterglow position (Sudilovsky et al. 2013, GCNC 15247) in any of the UVOT exposures. Preliminary 3-sigma upper limits, using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373), for the finding chart and summed exposures are presented below. --------------------------------------------------- Filter TSTART TSTOP Exposure Mag --------------------------------------------------- white (FC) 157 306 147 >21.4 u (FC) 315 564 246 >20.6 --------------------------------------------------- v 645 7269 381 >20.0 b 571 6121 170 >20.6 u 719 5983 274 >20.4 uvw1 5579 11,956 701 >21.1 uvm2 5374 11,436 1082 >21.2 uvw2 4964 7136 393 >20.7 white 595 6929 618 >22.0 --------------------------------------------------- The quoted upper limits have not been corrected for the expected extinction due to the Galactic reddening along the line of sight to this burst of E(B-V) = 0.02 mag (Schlafly et al. 2011, ApJS, 737, 103).