TITLE: GCN CIRCULAR NUMBER: 20478 SUBJECT: GRB 170115A: Swift/UVOT Upper Limits DATE: 17/01/17 16:39:49 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) 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 170115A 100 s after the BAT trigger (Page et al., GCN Circ. 20462). No optical afterglow consistent with the enhanced XRT position (Osborne et al. GCN Circ. 20465) 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) 100 250 147 >20.40 white 4804 6335 291 >20.66 v 5214 35195 816 >19.67 b 4599 40415 838 >20.68 u (fc) 260 328 67 >18.98 u 5829 6029 196 >19.65 uvw1 5624 5824 196 >19.32 uvm2 5419 5619 196 >19.37 uvw2 5009 11435 992 >20.69 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst (Schlegel et al. 1998).