TITLE:   GCN CIRCULAR
NUMBER:  7255
SUBJECT: GRB 080205: Swift XRT refined analysis
DATE:    08/02/05 17:45:32 GMT
FROM:    Rhaana Starling at U of Leicester  <rlcs1@star.le.ac.uk>

R.L.C. Starling (U. Leicester) and C.B. Markwardt (CRESST/GSFC/UMD) report 
on behalf of the Swift XRT team:

Swift XRT observations of GRB 080205 (trigger=302506) began 101 seconds 
after the BAT trigger (Markwardt et al., GCN 7250) in Windowed Timing mode 
and continued in Photon Counting (PC) mode 208 s after the trigger. The 
enhanced XRT position is given in Osborne et al. GCN 7252.

The light curve out to 13.5 ks post-trigger can be fit with a power law 
with two breaks. The initial steep decay has a slope of alpha1 = 4.5+/-0.3 
breaking at Tbk1 = 203+20/-8 s to a plateau with slope alpha2 = 0.4+/-0.4. 
The plateau phase ends at Tbk2 = 570+170/-120 s and the decay continues 
with alpha3 = 1.8+/-0.1.

We fit the first orbit PC mode spectrum, totalling 1.5ks of data and 
covering T0+208s-T0+1728s, with an absorbed power law. We measure a photon 
index of Gamma = 1.8+/-0.2 and intrinsic absorption of N_H = (1.0+/-0.7)e21 
cm^-2 (at z=0), whilst fixing the Galactic absorption at 7.1e20 cm^-2 
(Kalberla et al. 2005). 
The 0.5-10 keV observed (unabsorbed) flux is 6e-11 (7.2e-11) erg/cm^2/s. 
The count rate to flux conversion is approximately 1 count/s = 4.7e-11 
erg/cm^2/s.

The predicted count rate at T+24h is 2e-4 counts/s, or 1e-14 erg/cm^2/s.

This is an official product of the Swift XRT team.