[vsnet-grb-info 12303] GRB 120819A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13687
SUBJECT: GRB 120819A: Swift-XRT refined Analysis
DATE:    12/08/20 05:47:04 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

O.M. Littlejohns (U. Leicester), V. D'Elia (ASDC), A. Maselli 
(INAF-IASFPA), V. Mangano (INAF-IASFPA), D.N. Burrows (PSU), J.A.
Kennea (PSU), M.C. Stroh (PSU), J.P. Osborne (U. Leicester), K.L. Page
(U. Leicester) and A.P. Beardmore report on behalf of the Swift-XRT
team:

We have analysed 10 ks of XRT data for GRB 120819A (Beardmore  et al.
GCN Circ. 13681), from 159 s to 23.0 ks after the  BAT trigger. The
data comprise 67 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN. Circ 13684).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.75 (+0.12, -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.7 (+/-0.4). The
best-fitting absorption column is  3.3 (+2.0, -1.5) x 10^21 cm^-2, in
excess of the Galactic value of 8.9 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 4.2 x 10^-11 (6.0 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     3.3 (+2.0, -1.5) x 10^21 cm^-2
Galactic foreground: 8.9 x 10^20 cm^-2
Excess significance: 2.6 sigma
Photon index:	     1.7 (+/-0.4)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00531428.

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