[vsnet-grb-info 10179] GRB 110201A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11627
SUBJECT: GRB 110201A: Swift-XRT refined Analysis
DATE:    11/02/02 16:02:43 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe at astro.psu.edu>

D. Grupe and M. H. Siegel (PSU) report on behalf of the Swift-XRT team:


We have analyzed 21 ks of XRT data for GRB 110201A (Siegel  et al. GCN
Circ. 11622), from 54 s to 83.0 ks after the  BAT trigger. The data
comprise 6 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode. 

The light curve can be modeled with  a broken power-law model with an
initial decay slope of alpha-1 = 3.25 (+0.40, -0.66) and a break at
Tbreak-1 = 380 (+120, -55) s. After this break the afterglow decays
with a slope of alpha-2 = 1.03 (+0.12, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.04 (+0.26, -0.29). The
best-fitting absorption column is  3.1 (+0.5, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 2.8 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 4.3 x 10^-11 (7.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.1 (+0.5, -1.0) x 10^21 cm^-2
Galactic foreground: 2.8 x 10^20 cm^-2
Excess significance: 5.3 sigma
Photon index:	     2.04 (+0.26, -0.29)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00444230.

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