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.