GCN Circular 15708

A. A. Breeveld (UCL-MSSL) and J. L. Racusin (NASA/GSFC) report on behalf 
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140108A
78 s after the BAT trigger (Racusin et al., GCN Circ. 15699
Not found
 
 
).
A fading source consistent with the optical position (Gorbovskoy et al. 
GCN Circ. 15701
Not found
 
 
, Strobl et al. GCN Circ. 15703
Not found
 
 
) is detected in the 
initial UVOT exposures.

The preliminary detection and 3-sigma upper limits using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the finding chart (FC) and other early exposures are:

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

white_FC            78          228          147         20.17 � 0.20
white              571         1021          189        >21.3
v                  621         1420           97        >18.9
b                  547         1345           78        >19.8
u                  291         1320          304        >20.6
w1                 670         1462           90        >20.3
m2                 646         1444           97        >19.8
w2                 596         1395           83        >20.2

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 1.00 in the direction of the 
burst (Schlegel et al. 1998).