TITLE: GCN CIRCULAR NUMBER: 18922 SUBJECT: GRB 160121A: Swift/UVOT Upper Limits DATE: 16/01/22 09:26:13 GMT FROM: Samantha Oates at MSSL S. R. Oates (IAA-CSIC/UCL-MSSL) and L. M. Z. Hagen (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160121A 152 s after the BAT trigger (Hagen et al., GCN Circ. 18912). No optical afterglow consistent with the optical position reported by MOA (Oates et al., GCN Circ. 18917) 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 u_FC 152 401 246 >19.7 v 435 830 78 >18.6 u 152 918 356 >19.9 w1 484 754 58 >18.3 m2 459 854 78 >18.4 w2 410 805 78 >18.5 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 (Schlafly and Finkbeiner 2011).