GCN Circular 15056

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

The Swift/UVOT began settled observations of the field of GRB 130727A
3495 s after the BAT trigger (Stroh et al., GCN Circ. 15046
Not found
 
 
).
A source consistent with the XRT position (Goad et al. GCN Circ. 15051
Not found
 
 
)
is detected in initial UVOT Finding Chart (FC) exposure taken in white
filter, and it is also detected in summed UVOT exposures taken with white
and u filters. The same source is marginally detected (confidence level
~2 sigma) in b and uw1 filters.

Its UVOT position (J2000) is

RA = 22h 03m 11.62s = 330.79842
Dec = -65d 32m 18.8s = -65.53856.

with an estimated uncertanties of 0.7 arcseconds. The position of the
optical source is consistent with that given by the Faulkes Telescope
(Guidorzi et al., GCN 15050
Not found
 
 
).

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          3495         3645          147          21.27 � 0.34
white             3495         4876          344          21.35 � 0.24
v                 3651        16978          880         >20.96
b                 4471         4671          197          21.44 � 0.60
u                 4266        11215          934          20.99 � 0.26
w1                4061        10452         1082          21.89 � 0.54
m2                3856         5452          355         >20.50
w2                4882        16473         1082         >21.80

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).