TITLE: GCN CIRCULAR NUMBER: 19168 SUBJECT: GRB 160310A: Swift/UVOT Upper Limits DATE: 16/03/11 22:47:55 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and A. Maselli (INAF/IASF) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160310A 40247 s after the LAT trigger (Vianello et al., GCN Circ. 19158). No source is detected in the initial UVOT exposures at a position consistent with the position of the possible XRT afterglow (Gibson et al., GCN Circ. 19162) or the possible optical counterpart (Kruehler et al., GCN Circ. 19164). Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 40247 46726 1273 >20.4 white 41072 41890 805 >21.3 v 41897 42757 843 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.53 in the direction of the burst (Schlegel et al. 1998).