TITLE: GCN CIRCULAR NUMBER: 19593 SUBJECT: GRB 160625A: Swift/UVOT Upper Limits DATE: 16/06/26 20:48:32 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale (UCL-MSSL) and A. Maselli (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160625A 7183 s after the BAT trigger (Maselli et al., GCN Circ. 19577). No optical afterglow consistent with the XRT position (Burrows et al. GCN Circ. 19578) is detected in the UVOT exposures. We note the presence of a source approximately 3'' from the XRT position. This source is present in the USNO catalogue. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 7183 7952 344 >20.8 v 8163 8363 197 >19.0 b 7548 7747 197 >19.9 u 7342 7542 197 >19.4 m2 8368 8483 113 >18.9 w2 7958 8158 197 >19.6 The magnitudes in the table are not corrected for the substantial Galactic extinction due to the reddening of E(B-V) = 1.51 in the direction of the burst (Schlegel et al. 1998). -- Dr. Massimiliano De Pasquale Research associate - Swift UVOT scientist Mullard Space Science Laboratory, University College London