[vsnet-grb-info 6427] GRB 080727C: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8041
SUBJECT: GRB 080727C: Swift XRT refined analysis
DATE:    08/07/28 11:53:51 GMT
FROM:    Rhaana Starling at U of Leicester  <rlcs1 at star.le.ac.uk>

R.L.C. Starling (U. Leicester) and A.M. Parsons (GSFC) report on behalf of 
the Swift XRT team:

We have analysed the first five orbits of Swift XRT data for GRB 080727C 
(trigger=318170, Parsons et al. GCN Circ. 8035) beginning at T0+79 s until 
T0+22.6 ks. The enhanced XRT position is given in Osborne et al. 
(GCN Circ. 8038).

Up to approximately T0+110 s the light curve appears to be flat. 
Thereafter the light curve can be fitted with a broken power law with 
alpha1 = 1.5+/-0.1, breaking at Tbk = 740 +1880/-370 s to a slightly 
shallower decay of alpha2 = 1.2 +0.1/-0.3. 

The Photon Counting mode spectrum consisting of 502 s of data during the 
first orbit is well fitted with an absorbed power law of photon index 
Gamma = 1.4+/-0.3 and intrinsic absorption (assuming z=0) of N_H = (1.2 
+0.5/-0.2) e22 cm-2 in addition to the high Galactic absorption in this 
direction of N_H = 6.8e21 cm-2 (Kalberla et al. 2005). 
We measure an average observed (unabsorbed) 0.3-10 keV flux over this time 
of 1.1e-10 (1.7e-10) erg/cm2/s corresponding to an observed count rate to 
flux conversion of 1 count/s = 9.9e-11 erg/cm2/s.

The predicted count rate at T+24 hr is 0.001 count/s corresponding to an
observed 0.3-10 keV flux of 1.35e-13 erg/cm2/s, assuming the decay 
continues with alpha=1.2.

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