GCN Circular 14887

A. A. Breeveld (MSSL-UCL) 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 130612A 94 
s after the BAT trigger (Racusin et al., GCN Circ. 14874
Not found
 
 
).
A fading source consistent with the XRT position (Beardmore et al. GCN 
Circ. 14884
Not found
 
 
) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  17:19:10.58 = 259.79408 (deg.)
     Dec (J2000) = +16:43:11.9  =  16.71996 (deg.)
with an estimated uncertainty of 0.53 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the early exposures are:

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

white               94          185           89         18.97 � 0.07
v                  763         7763          549        >20.6
b                  688        13692         1307        >21.3
u                  664         1655          117         19.68 � 0.24
w1                 639        18651         2143        >21.6
m2                 614        17743         1406        >21.6
w2                 738         7559          549        >21.1

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.08 in the direction of the 
burst (Schlegel et al. 1998).