TITLE:   GCN CIRCULAR
NUMBER:  17157
SUBJECT: GRB 141207A: Swift-XRT afterglow candidate detection
DATE:    14/12/10 20:56:07 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, K.L. Page & A. Amaral-Rogers (U. Leicester) report on behalf 
of the Swift-XRT team:

Swift has continued to observe the field of the Fermi-LAT GRB 141207A 
(Arimoto et al., GCN Circ. 17146). The uncatalogued X-ray source 
reported by Amaral-Rogers & Evans (GCN. Circ 17149) shows no evidence of 
fading.

An additional uncatalogued X-ray source has also been detected at 
RA,Dec=159.8547, 3.71139 degrees, which is equivalent to:

RA (J2000)  = 10h 39m 25.13s
Dec (J2000) = +03d 42' 41.0"

with an uncertainty of 4.9 arcsec (radius, 90% confidence). This source 
was initially detected with a count-rate of 0.012 +/- 0.003 ct/sec. In a 
second observation, from T0+191 ks to T0+231 s, the source has faded to 
a count-rate of 1.0 (+/-0.5) x 10^-3 ct/sec. We therefore suggest that 
this is likely the afterglow of GRB 141207A.

The PC mode spectrum of this source can be fitted with an absorbed 
power-law with a photon index of 2.1 (+1.5, -0.7). The best-fitting 
absorption column is 5.2 (+18, -4.8) x 10^21 cm^-2, consistent with the 
Galactic value of 0.4 x 10^21 cm^-2 (Willingale et al. 2013).

A summary of the PC-mode spectrum is thus:

Total column:	     5.2 (+18, -4.8) x 10^21 cm^-2
Galactic foreground: 3.7 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.1 (+1,5, -0.7)

This circular is an official product of the Swift-XRT team.