[vsnet-grb-info 12582] GRB 121031A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13946
SUBJECT: GRB 121031A: Swift-XRT refined Analysis
DATE:    12/11/02 16:48:38 GMT
FROM:    Valerio D'Elia at ASDC  <delia at asdc.asi.it>

V. D'Elia (ASDC) reports on behalf of the Swift-XRT team:

We have analysed 9.2 ks of XRT data for GRB 121031A (D'Elia  et al. GCN
Circ. 13934), from 68 s to 22.6 ks after the  BAT trigger. The data
comprise 276 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 13935, 13944).

The late-time light curve (from T0+4.7 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.86 (+/-0.07).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.03 (+/-0.08). The
best-fitting absorption column is  4.6 (+0.4, -0.3) x 10^21 cm^-2, in
excess of the Galactic value of 4.0 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.33 (+/-0.10) and a
best-fitting absorption column of 5.2 (+/-0.4) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.9 x 10^-11 (9.1 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     5.2 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 4.0 x 10^20 cm^-2
Excess significance: 18.5 sigma
Photon index:	     2.33 (+/-0.10)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00537195.

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