GCN Circular 11721

G. Stratta (ASDC) and V. D'Elia (ASDC) report on behalf of the
Swift-XRT team:

We have analysed 22 ks of XRT data for GRB 110213A (D'Elia  et al. GCN
Circ. 11705
Not found
 
 
), from 81 s to 54.5 ks after the  BAT trigger. The data
comprise 121 s in Windowed Timing (WT) mode (the first 8 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 Osborne et
al. (GCN. Circ 11712).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=5.2 (+0.5, -0.4). At T+141 s  the decay
flattens to an alpha of -0.22 (+0.10, -0.14). The light curve breaks
again at T+1489 s to a decay with alpha=1.10 (+0.07, -0.08),  before a
final break at T+9954 s s after which the decay index is 2.14 (+0.10,
-0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.11 (+/-0.07). The
best-fitting absorption column is  2.81 (+0.24, -0.23) x 10^21 cm^-2,
in excess of the Galactic value of 2.2 x 10^21 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.1 x 10^-11 (6.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.81 (+0.24, -0.23) x 10^21 cm^-2
Galactic foreground: 2.2 x 10^21 cm^-2
Excess significance: 20.5 sigma
Photon index:	     2.11 (+/-0.07)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00445414.

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