GCN Circular 18892
L. M. Z. Hagen (PSU) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160117A 68.7 ks after the BAT trigger (Markwardt et al. GCN Circ. 18874). No optical afterglow consistent with the XRT position of Source 1 (Maselli et al. GCN Circ. 18888) 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 exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag v 75251 76158 885 >19.75 u 70499 70799 295 >19.80 w1 69593 80420 1226 >20.52 m2 68687 76854 1565 >20.90 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).