TITLE: GCN CIRCULAR NUMBER: 15972 SUBJECT: GRB 140311B: Swift/UVOT Upper Limits DATE: 14/03/12 19:26:59 GMT FROM: Stephen Holland at STScI S. T. Holland (STScI) and J. L. Racusin (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 140311B 3398 s after the BAT trigger (Racusin et al. 2014, GCNC 15945). We do not detect any new source consistent with the Nansan afterglow position (Xu et al. 2014, GCNC 15949) 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) 3398 3548 147 >21.2 --------------------------------------------------- v 3555 5191 393 >20.0 b 4375 5990 372 >20.4 u 4170 5806 393 >20.2 uvw1 3965 5601 393 >20.3 uvm2 3760 5396 393 >20.2 uvw2 4787 4986 197 >20.1 white 4580 4780 197 >21.4 --------------------------------------------------- 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) = 0.05 mag (Schlafly et al. 2011, ApJS, 737, 103).