GCN Circular 8252

E. A. Hoversten (PSU) and G. Stratta (ASDC) report on behalf of the
Swift UVOT team:

The Swift/UVOT began settled observations of the field of
GRB 080916B, 1359s after the BAT trigger (Stratta et al., GCN 8240
Not found
 
 
).
There is a possible detection of an afterglow in the UVOT white filter
at:

     RA (J2000)  10:54:39.78
    Dec (J2000)  69: 3:57.9

with an estimated uncertainty of 0.8 arcsec (radius, 90% confidence).
This position is consistent with the UVOT enhanced XRT position (Evans
et al., GCN 8247
Not found
 
 
).  The afterglow candidate does not appear in the DSS
images, and photometry from the second orbit of Swift observations
suggests that it has faded.

UVOT magnitudes and 3-sigma upper limits are reported in the following
table:

Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-----------------------------------------------------
white    1359.0    1458.8    98.2   20.50 +/- 0.21
white    7826.0    8025.7   196.6     > 21.27
v        1340.9    2920.7   342.1     > 19.62
b        1516.3    2676.5   155.6     > 20.32
u        1491.6    2651.7   155.6     > 19.91
uvw1     1467.3    2627.3   155.5     > 19.91
uvm2     1604.9    3076.8   285.0     > 20.06
uvw2     1556.0    2716.0   155.5     > 19.91

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight of E_{B-V} = 0.02 mag.
All photometry is on the UVOT flight system described in Poole et al.
(2008, MNRAS, 383, 627).