GCN Circular 9678

A. Breeveld (MSSL/UCL) and L. Vetere (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090715B
53 s after the BAT trigger (Vetere et al., GCN Circ. 9668
Not found
 
 
).
The optical afterglow reported in Vetere et al., GCN 9668
Not found
 
 
 and  
confirmed by Smith et al., GCN 9670
Not found
 
 
, Malesani et al., GCN 9671
Not found
 
 
,  
Wiersema et al., GCN 9673
Not found
 
 
 and Antonelli et al., GCN 9675
Not found
 
 
 is detected  
by the UVOT only in the initial white exposure. The detected magnitude  
and preliminary 3-sigma upper limits obtained using a 3" aperture and  
the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposure and subsequent summed exposures are:

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

white_FC         53            203          147         20.37 +/- 0.15
white            4052         4252          196         >21.3
v                    5989       22687          795         >21.0
b                    3848         4047          197         >20.3
u                      266       16495          428         >21.2
w1              12053       16278          894         >21.2
m2                6195       10367          826         >21.0
w2                4258       22065          995         >21.4

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).