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GCN Circular 15313

Subject
GRB 131004A: Swift/UVOT Detection
Date
2013-10-05T16:42:18Z (11 years ago)
From
MSSL Swift/UVOT team at MSSL/Swift <msslba@googlemail.com>
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).
A source consistent with the XRT position (Evans et al. GCN Circ. 15308)
and the position of the source given in Xu et al. (GCN Circ. 15304)
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).
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