GCN Circular 11541

B. Sbarufatti (INAF-OAB/IASFPA) reports on behalf of the Swift-XRT
team:

We have analysed 6.2 ks of XRT data for GRB 110106B (Sbarufatti  et al.
GCN Circ. 11525
Not found
 
 
), from 339 s to 30.3 ks after the  BAT trigger. The
data comprise 24 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN. Circ 11532).

The light curve can be modelled with a series of power-law decays. The
light curve initially rises, with an index alpha=-1.5 (+0.0, -1.3). At
T+470 s it breaks to an alpha of 0.64 (+/-0.07) before breaking again
at T+14354 s to a final decay with index alpha=1.6 (+1.0, -0.5).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.20 (+/-0.16). The
best-fitting absorption column is  2.08 (+0.44, -0.22) x 10^21 cm^-2,
in excess of the Galactic value of 2.4 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.8 x 10^-11 (6.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.08 (+0.44, -0.22) x 10^21 cm^-2
Galactic foreground: 2.4 x 10^20 cm^-2
Excess significance: 15.4 sigma
Photon index:	     2.20 (+/-0.16)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00441676.

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