[vsnet-grb-info 14278] GRB 131209A: Swift XRT and UVOT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15592
SUBJECT: GRB 131209A: Swift XRT and UVOT observations 
DATE:    13/12/11 16:28:07 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <dxg35 at psu.edu>

Dirk Grupe (PSU) and Alice Breeveld (MSSL) report on behalf of the 
Swift team:

We report on Swift observations of the field of the FERMI/LAT-
discovered GRB 131209A (Vianello et al., GCN circ. 15587) starting
26.5 hours after the FERMI/LAT trigger. Swift  performed three 
observations with and exposure tome of 3 ks each to cover most of 
the IPN error box reported by Hurley et al. (GCN circ. 15588). 
We found two X-ray sources with in the IPN error box, one 
of which coincides with a radio source, NVSS J090753-333724. The
second source at the position 
 
RA-2000:   09 07 19.2 
Dec-2000: -33 51 20.0

does not have an entry in the NED or Simbad. Its count rate in the
XRT is at a level of (4.7+/-1.9)e-3 counts/s which is equivalent to
a flux in the 0.3-10 keV band of (1.9+/-0.7)e-13 erg/s/cm2.
Swift started observing the tile that covered this source 33 hours
after the Fermi/LAT trigger (Vianello et al., GCN Circ. 15587). 

Only one of the XRT potential candidate 
sources (source 2) is in the field of view of the UVOT and there 
is no new source found at this position. Preliminary 3-sigma upper 
limits using the UVOT photometric system (Breeveld et al. 2011, 
AIP Conf. Proc. 1358, 373) for the initial summed exposures are:

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

white        33.16          33.37          754         >21.8
v            33.37          33.60          801         >20.1
u            32.94          34.78         1367         >21.1

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.36 in the direction 
of the burst (Schlegel et al. 1998).