[vsnet-grb-info 24000] GRB 191029A: CORRECTED Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26099
SUBJECT: GRB 191029A: CORRECTED Swift-XRT refined analysis
DATE:    19/10/30 09:56:42 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

P.A. Evans and K.L. Page (U. Leicester) report on behalf of the
Swift-XRT team:

The XRT refined analysis for GRB 191029A, given in GCN 26094 was
incorrect. There is an AGN within the BAT error circle and unfortunately
the automated light curve and spectral analysis had been performed for
this source, rather than the afterglow.

The correct refined analysis is below. We apologise for any
inconvenience.

We have analysed 13 ks of XRT data for GRB 191029A (Evans et al. GCN
Circ. 26088), from 3.1 ks to 62.0 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Evans et al. (GCN Circ. 26095).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.77 (+0.13, -0.12).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.81 (+0.23, -0.19). The
best-fitting absorption column is  3.4 (+5.3, -1.6) x 10^20 cm^-2,
consistent with the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 3.5 x 10^-11 (3.7 x
10^-11) erg cm^-2 count^-1.

A summary of the PC-mode spectrum is thus:
Total column:        3.4 (+5.3, -1.6) x 10^20 cm^-2
Galactic foreground: 1.8 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:        1.81 (+0.23, -0.19)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00932058.