TITLE: GCN CIRCULAR NUMBER: 19589 SUBJECT: GRB 160625B: Swift/UVOT Detection DATE: 16/06/26 11:15:45 GMT FROM: Samantha Oates at MSSL GRB 160625B: Swift/UVOT Detection S. R. Oates (U. Warwick) and A. D'Aì (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160625B 9616 s after the LAT trigger (Dirirsa et al., GCN Circ. 19580). A source consistent with the RATIR position (Troja et al. GCN Circ. 19588) and the edge of the XRT position (Melandri et al. GCN Circ. 19585) is detected in the initial UVOT exposures. Preliminary detections 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 u 9616 9978 353 16.41 +/- 0.04 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).