TITLE: GCN CIRCULAR NUMBER: 15997 SUBJECT: GRB 140318A: Swift/UVOT Upper Limits DATE: 14/03/19 14:07:38 GMT FROM: Mike Siegel at PSU/Swift MOC B. Porterfield (PSU) and Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 140318A 132 s after the BAT trigger (Cenko et al., GCN Circ. 15986). No optical afterglow consistent with the XRT position (Cenko et al. GCN Circ. 15986) or NOT position (Schulze et al., GCN Circ 15987) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 132 282 147 >21.2 white 132 5340 541 >21.9 v 4115 5750 393 >19.6 b 3499 5135 393 >20.9 u 4730 4930 197 >20.1 w1 4525 6063 298 >20.5 m2 4320 5955 393 >21.2 w2 3910 5546 393 >20.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).