[vsnet-grb-info 5932] GRB 080409: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7578
SUBJECT: GRB 080409: Swift XRT refined analysis
DATE:    08/04/09 11:53:54 GMT
FROM:    Rhaana Starling at U of Leicester  <rlcs1 at star.le.ac.uk>

R.L.C. Starling, P.A. Evans, K.L. Page (U. Leicester) and S.T. Holland 
(CRESST/USRA/GSFC) report, on behalf of the Swift XRT team:

We have analysed the first three orbits of Swift XRT data (5.8 ks of data 
from T0+96s to T0+1.29e4s) for GRB 080409 (Holland et al., GCN Circ. 
7573). The enhanced position for the X-ray afterglow is given in Evans et 
al. (GCN Circ. 7575).

The light curve shows an initial increase with slope of alpha1~0.6 up to
T~480s. The light curve then turns over to decay with a slope of
alpha2=-0.8+/-0.1.  

The Photon Counting mode spectrum collected from the first three orbits 
can be fit with an absorbed power law of photon index Gamma=2.2+0.5/-0.7 
and a total absorbing column of NH=(5 +5/-4)e21 cm-2, exceeding the 
Galactic value of 2.4e21 cm-2. The 0.3-10 keV observed (unabsorbed) flux 
is 3.2e-12 (6.7e-12) erg/cm2/s, corresponding to a count rate of 5.8e-2 
count/s and a count rate to flux conversion of 1 count/s = 5.6e-11 erg/cm2/s.

The predicted count rates at T0+24h and T0+48h are 6.8e-3 and 4.0e-3 
count/s respectively, assuming the decay continues with alpha=-0.8.

This is an official product of the Swift XRT team.