GCN Circular 9786

P. Schady (MSSL-UCL) and J.R. Cummings (NASA/UMBC) report on behalf of the 
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090813 88s 
after the BAT trigger (Cummings et al., GCN Circ 9781). No new source is 
detected within the XRT error circle or at the optical position reported 
by Cenko (GCN Circ. 9783
Not found
 
 
) in any of the individual or combined UVOT 
filters.

The 3-sigma upper limits of detected a source at the position of the 
optical afterglow reported by Cenko (GCN Circ. 9783
Not found
 
 
) in the first white 
band finding chart (fc) observation, and in consecutive coadded 
observations for each of the UVOT filters are as follows:

Filter  T_start(s)  T_stop(s)  Exp(s)  Mag 3-sig UL
wh (fc)    88         237      147       > 20.55
wh         581        1894     264       > 21.35
vv         631        1943     156       > 19.39
bb         556        1869     136       > 20.29
uu         300        2017     382       > 20.44
w1         681        1992     156       > 19.73
m2         656        1967     156       > 19.41
w2         607        1919     156       > 19.83

The values quoted above are not corrected for the Galactic extinction due 
to the large reddening of E(B-V) = 0.17 in the direction of the burst 
(Schlegel et al., 1998). The photometry is on the UVOT photometric system 
described in Poole et al. (2008, MNRAS, 383, 627).