TITLE: GCN CIRCULAR NUMBER: 20016 SUBJECT: GRB 161007A: Swift/UVOT Upper Limits DATE: 16/10/08 17:29:28 GMT FROM: Lea Hagen at PSU L. M. Z. Hagen (PSU) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 161007A 133 s after the BAT trigger (D'Elia et al., GCN Circ. 20008). No optical afterglow consistent with the XRT position (Goad et al., GCN Circ. 20013) or the possible GTC optical counterpart (de Ugarte Postigo et al., GCN Circ. 20014) 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 early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 133 1716 411 >20.79 v 621 1593 116 >18.39 b 547 1691 116 >19.26 u 291 1666 343 >19.73 uvw1 671 1642 116 >18.69 uvm2 646 1617 116 >18.81 uvw2 596 1735 129 >19.04 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.12 in the direction of the burst (Schlegel et al. 1998).