TITLE:   GCN CIRCULAR
NUMBER:  35128
SUBJECT: GRB 231117A: Swift-XRT refined Analysis
DATE:    23/11/19 19:28:53 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), D.N. Burrows (PSU), A.P. Beardmore (U.
Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB) and
P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 8.8 ks of XRT data for GRB 231117A, from 85 s to 223.3
ks after the  BAT trigger. The data comprise 9 s in Windowed Timing
(WT) mode (taken while Swift was slewing), with the remainder in Photon
Counting (PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.65 (+0.07, -0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.81 (+0.17, -0.13). The
best-fitting absorption column is  consistent with the Galactic value
of 6.1 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 3.6 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.1 (+/-3.8) x 10^20 cm^-2
Galactic foreground: 6.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.81 (+0.17, -0.13)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01197027.

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