[vsnet-grb-info 1762] GRB050713b: XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3602
SUBJECT: GRB050713b: XRT refined analysis
DATE:    05/07/13 21:37:29 GMT
FROM:    David Burrows at PSU/Swift  <dxb15 at psu.edu>

K. Page, S. Vaughan, M. Goad (Leicester), D. N. Burrows (PSU), M. Ajello 
(MPE), R. Fink and N. Gehrels (GSFC) report on behalf of the Swift XRT team:

We have analysed the first two orbits of data for GRB050713b (GCN 3590, 
Vaughan et al., 2005).  Using xrtcentoid, the refined position is:

RA(J2000) = 20h 31m 15.5s
Dec(J2000) = +60d 56' 40.4"

with an uncertainty of 6 arcsec. This is only 2 arcsec from the original 
XRT position (GCN 3590, Vaughan et al., 2005).

The light-curve shows a steeply fading afterglow during the first orbit, 
with a decay slope of
alpha = 2.88 +/- 0.12 between 143 and 600 seconds after the trigger.  After 
~5000 seconds (i.e. on the second orbit), the light-curve flattens 
significantly; more data are required to constrain the slope following the 
break in the light curve.

The WT spectrum can be fitted by an absorbed power-law with a spectral
index, Gamma = 1.70 +0.11/-0.09 and excess NH of (1.97 +0.50/-0.43)e21
cm^-2.

The unabsorbed 0.3-10 keV flux (averaged over 143 and 330 seconds after
the burst) is (9.02 +0.16/0.80)e-10 erg cm^-2 s^-1.