GCN Circular 15093

A. A. Breeveld (UCL-MSSL) and V. D'Elia (ASDC) report on behalf of the 
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 130812A 
139 s after the BAT trigger (D'Elia et al., GCN Circ. 15088
Not found
 
 
).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 15089
Not found
 
 
) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system 
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding 
chart (FC) exposure and subsequent exposures are:

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

u_FC               139          389          246         >20.3
v                  445        12868         1191         >20.5
b                  394        11236         1459         >21.7
u                  139         7030          884         >20.8
w1                 494         6825          491         >20.5
m2                 469         6619          452         >20.3
w2                 421        12142         1376         >21.3

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.23 in the direction of the 
burst (Schlegel et al. 1998).