GCN Circular 15313

M. De Pasquale (UCL-MSSL) and L. M. Z. Hagen (PSU) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 131004A
75 s after the BAT trigger (Hagen et al., GCN Circ. 15303
Not found
 
 
).
A source consistent with the XRT position (Evans et al. GCN Circ. 15308
Not found
 
 
)
and the position of the source given in Xu et al. (GCN Circ. 15304
Not found
 
 
)
is detected in the initial and summed UVOT exposures.

The preliminary coordinates of this source are:

    RA  (J2000) =  19:44:27.09 = 296.11287 (deg.)
    Dec (J2000) = -02:57:30.4  =  -2.95844 (deg.)

with an estimated uncertainty of 0.55 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_FC            75          225          147         19.23 �� 0.11
white               75         5688          520         20.18 �� 0.12

u_FC               288          537          246         19.96 �� 0.34
u                  288         6715          659         20.72 �� 0.40

v                  617         6100          432         >20.24
b                  543         6770          285         >21.0

w1                 666         6510          432         >20.9
m2                 814         6305          413         >20.8
w2                 593         5895          432         >21.0


The magnitudes in the table are not corrected for substantial Galactic
extinction
due to the reddening of E(B-V) = 0.28 in the direction of the burst
(Schlegel et al. 1998).