[vsnet-grb-info 2241] GRB051008: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4080
SUBJECT: GRB051008: Swift XRT refined analysis
DATE:    05/10/10 16:38:55 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri at asdc.asi.it>

M. Perri, M. Capalbi (ASDC), D. N. Burrows, J. Kennea (PSU), D. Hinshaw
(GSFC-SPSYS), P. Meszaros (PSU) report on behalf of the Swift XRT team:

We have analysed the first 22 orbits of Swift XRT data for GRB 051008
(Marshall et al., GCN 4069). XRT observations began in Photon Counting
(PC) mode 3038 seconds after the BAT trigger.

The 0.3-10 keV light curve of the X-ray afterglow (Perri et al., GCN
4073) in the time interval 3-120 ks after the trigger is well fitted by
a broken power-law model with decay indices alpha_1=-0.86+/-0.07,
alpha_2=-2.0+/-0.1 and temporal break t_b=16.5+/-2.1 ks.

The 0.3-10 keV X-ray spectrum in the time interval 3-40 ks after the
trigger is well described by an absorbed power-law model with photon
index Gamma=1.9+/-0.1. The derived NH is (3.1+/-0.5)E21 cm^-2, which is
higher than the Galactic value (1.05E20 cm^-2, Dickey & Lockman 1990).

Extrapolating the light curve at later times, we estimate the unabsorbed
flux in the 0.3-10 keV energy band to be ~8E-14 ergs/s/cm^2 48 hours
after the burst.