GCN Circular 9751

C. A. Swenson (PSU) and Cannizzo (NASA/UMBC)report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090807
164 s after the BAT trigger (Cannizzo et al., GCN Circ. 9746
Not found
 
 
).
No optical afterglow consistent with the XRT position (Beardmore et al.,
GCN Circ. 9748
Not found
 
 
) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           164          313          147         >21.2
u_FC               322          571          246         >20.1
white              164         1026          295         >21.1
u                  322          571          246         >20.1

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.18 in the direction of the burst
(Schlegel et al. 1998).