TITLE: GCN CIRCULAR NUMBER: 22299 SUBJECT: GRB 180102A: Swift/UVOT Upper Limits DATE: 18/01/03 12:37:47 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180102A 74 s after the BAT trigger (Page et al., GCN Circ. 22292). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 22294) 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 74 224 147 >20.8 u_FC 286 535 246 >19.9 white 74 7508 824 >21.3 v 616 6484 352 >19.3 b 541 7303 529 >20.3 u 286 7098 717 >20.4 w1 665 6893 529 >20.1 m2 640 6688 350 >19.7 w2 591 7692 528 >20.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).