TITLE:   GCN CIRCULAR
NUMBER:  7375
SUBJECT: GRB 080307: Swift/UVOT Upper Limits 
DATE:    08/03/07 20:20:40 GMT
FROM:    Stephen Holland at USRA/NASA/GSFC/SSC  <sholland@milkyway.gsfc.nasa.gov>

S. T. Holland (CRESST/GSFC/USRA) reports on the behalf of the Swift
UVOT team:

        The Swift/UVOT observed the field of GRB 080307 starting 105 s
after the BAT trigger (Holland et al. 2008, GCN Circ. 7362).  We do not
find any source, in any of the UVOT observations, at the location of
the Gemini-North source (Tanvir, 2008 GCN Circ. 7369).

        The 3-sigma upper limits for detecting a source at this
location in the co-added images are:


Filter    T_start   T_stop    Exp(s)    Mag (3-sigma upper limit)
-----------------------------------------------------------------
   v         212      5754       676     >20.7
   b         691      6574       412     >21.4
   u         666      6369       432     >21.1
  uvw1       642      6164       432     >20.9
  uvm2       618      5959       413     >20.6
  uvw2       721      6816       245     >20.7
white       105      6779       599     >22.3
-----------------------------------------------------------------

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.03 mag.  All photometry is on the UVOT flight
system described in Poole et al. (2008, MNRAS, 383, 627).