[vsnet-grb-info 11037] GRB 111018A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12455
SUBJECT: GRB 111018A: Swift-XRT refined Analysis
DATE:    11/10/19 07:53:17 GMT
FROM:    Vanessa Mangano at INAF-IASFPA  <vanessa at ifc.inaf.it>

V. Mangano (INAF IASFPA) and F. E. Marshall (NASA/GSFC) reports on
behalf of the Swift-XRT team:

We have analysed 11 ks of XRT data for GRB 111018A (Marshall  et al.
GCN Circ. 12450), from 115 s to 36.2 ks after the  BAT trigger. The
data comprise 37 s in Windowed Timing (WT) mode (the first 6 s were
taken while Swift was slewing) with the remainder in Photon Counting
(PC) mode. The enhanced XRT position for this burst was given by Goad
et al. (GCN. Circ 12453).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.01 (+0.15, -0.13).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+0.8, -0.7). The
best-fitting absorption column is  1.2 (+0.8, -0.6) x 10^22 cm^-2, in
excess of the Galactic value of 2.5 x 10^21 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 6.7 x 10^-11 (1.2 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.2 (+0.8, -0.6) x 10^22 cm^-2
Galactic foreground: 2.5 x 10^21 cm^-2
Excess significance: 3.4 sigma
Photon index:	     1.8 (+0.8, -0.7)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00505801.

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