[vsnet-grb-info 2395] GRB051109B: XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4232
SUBJECT: GRB051109B: XRT refined analysis 
DATE:    05/11/09 18:42:43 GMT
FROM:    Gianpiero Tagliaferri at OAB-INAF  <taglia at merate.mi.astro.it>

G. Tagliaferri (INAF-OAB), S. Campana (INAF-OAB),
P. Romano (INAF-OAB), T. Mineo (INAF-IASFPA),
D.N. Burrows (PSU) report on behalf of the Swift/XRT team:

We have analysed 4.3 ks of XRT observations of the afterglow of
GRB051109B (Tagliaferri et al., GCN 4222; Campana et al. GCN4226).

The X-ray light-curve from 100s after the burst up to about 10 ks
after the burst is quite flat and well represented by a single power
law with a decay index alpha=-0.55+/-0.08 (90% containment).

The spectrum  can be modeled with a power-law with photon index
Gamma = 2.33+/-0.30 (90% containment). There is evidence for an
absorbing column higher than the Galactic value (1.3e21 cm^-2)
at a level of (3.1+/-1.2)e21 cm^-2.

At 200 s the 0.5-10 keV unabsorbed flux was 1.7e-10 erg cm^-2 s^-1.
At 10000 s the afterglow had faded to flux level of 2.0e-11 erg cm^-2 s^-1.
Assuming the current flat  decay we predict a flux of ~5.6e-13 erg cm^-2 
s^-1
at 1 d from the burst.