GCN Circular 6546
M. De Pasquale (MSSL/UCL), R. Starling (Univ. Leicester) and P. Schady (MSSL/UCL) report, on the behalf ot the Swift UVOT team: The Swift UVOT telescope began its White filter finding chart exposure of GRB070616 (Starling et al., GCN circ 6542) 144 seconds after the trigger. The XRT position lies on a bright object, listed in the USNO-B1.0 catalogue, therefore we caution that this source strongly affects the photometry. In the XRT error circle we do not detect any optical afterglow. We derive the following 3 sigma upper limits: Filter Time after trigger (s) Exposure (s) 3s U.L. White 144-243 98 18.3 V 250-649 390 18.1 White 144-979 209 18.6 V 250-1122 547 18.3 B 729-738 10 17.1 U 707-874 39 17.2 UW1 680-850 39 17.1 UM2 655-825 39 17.3 UW2 758-777 20 17.0 No correction has been made for the high Galactic reddening of E(B-V)=0.4. We note that this value should be taken with caution, having the burst occurred at low Galactic latitude.