GCN Circular 11644

A. P. Beardmore (U Leicester) reports on behalf of the Swift-XRT team:

We have analysed 14 ks of XRT data for GRB 110205A (Beardmore  et al.
GCN Circ. 11629
Not found
 
 
), from 145 s to 30.7 ks after the  BAT trigger. The
data comprise 737 s in Windowed Timing (WT) mode (the first 9 s were
taken while Swift was slewing) with the remainder in Photon Counting
(PC) mode. The enhanced XRT position for this burst was given by
Beardmore et al. (GCN. Circ 11639).

The light curve comprises a number of flares (at ~T0+145 s, T0+175 s to
T0+275 s, T0+615 s) followed by a power-law decay. The late-time light
curve (from T0+5.1 ks) can be modelled with  a power-law decay with a
decay index of alpha=1.63 (+/-0.10).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.420 (+/-0.020). The
best-fitting absorption column is  4.2 (+/-0.6) x 10^21 cm^-2, at a
redshift of 2.22, in addition to the Galactic value of 1.6 x 10^20
cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index
of 1.99 (+0.08, -0.07) and a best-fitting absorption column of 3.5
(+1.6, -1.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10
keV flux conversion factor deduced from this spectrum  is 3.7 x 10^-11
(4.2 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.6 x 10^20 cm^-2
Intrinsic column:    3.5 (+1.6, -1.5) x 10^21 cm^-2 at z=2.22
Photon index:	     1.99 (+0.08, -0.07)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00444643.

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