[vsnet-grb-info 12437] GRB 120923A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13812
SUBJECT: GRB 120923A: Swift-XRT refined Analysis
DATE:    12/09/24 05:28:05 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at star.le.ac.uk>

J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P. Beardmore
(U. Leicester), P.A. Evans (U. Leicester), O.M. Littlejohns (U.
Leicester), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), P.
D'Avanzo (INAF-OAB) and V.N. Yershov report on behalf of the Swift-XRT
team:

We have analysed 9.0 ks of XRT data for GRB 120923A (Yershov  et al.
GCN Circ. 13796), from 151 s to 57.5 ks after the  BAT trigger. The
data comprise 331 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN. Circ 13801).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=0.84 (+0.11, -0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.78 (+0.47, -0.26). The
best-fitting absorption column is  1.08 (+1.30, -0.10) x 10^21 cm^-2,
consistent with the Galactic value of 9.8 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 4.2 x 10^-11 (5.1 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.08 (+1.30, -0.10) x 10^21 cm^-2
Galactic foreground: 9.8 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.78 (+0.47, -0.26)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00534402.

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