GCN Circular 9908

P.A. Curran (MSSL-UCL) and T. N. Ukwatta (GSFC/GWU) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090912 796s after 
the BAT trigger (Ukwatta et al., GCN 9905
Not found
 
 
). No optical afterglow consistent 
with the enhanched Swift XRT position (Beardmore et al., GCN 9906
Not found
 
 
)  is detected 
in the 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) and subsequent exposures are:


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

white          796          946           147         >20.50 (FC)
white          796          7707          608         >21.09
v              1129         8118          294         >19.04
b              1228         7502          254         >19.91
u              1204         7297          313         >19.58
w1             1179         7092          313         >19.82
m2             6688         8273          344         >19.78
w2             7713         7913          197         >19.78

The values quoted above are not corrected for the Galactic extinction due to 
the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 
1998).