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GCN Circular 26144

Subject
GRB 191101A: Swift-XRT refined Analysis
Date
2019-11-02T06:34:50Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J. D. Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), M. Capalbi (INAF-IASFPA), M.
Perri (ASDC), V. D'Elia (ASDC), A. Tohuvavohu (U. Toronto), J.A. Kennea
(PSU) and A. D'Ai report on behalf of the Swift-XRT team:

We have analysed 7.9 ks of XRT data for GRB 191101A (D'Ai et al. GCN
Circ. 26135), from 92 s to 24.5 ks after the  BAT trigger. The data
comprise 190 s in Windowed Timing (WT) mode (the first 5 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 Beardmore
et al. (GCN Circ. 26137). The late-time light curve (from T0+4.8 ks) is
consistent with a constant source of mean count rate 4.8e+00 ct/sec. A
power-law fit gives an index of 0.18 (+0.22, -0.21).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.28 (+/-0.05). The
best-fitting absorption column is  9.9 (+1.2, -1.1) x 10^20 cm^-2, in
excess of the Galactic value of 1.3 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.08 (+0.15, -0.14)
and a best-fitting absorption column of 6.2 (+3.2, -2.9) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.1 x 10^-11 (3.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.2 (+3.2, -2.9) x 10^20 cm^-2
Galactic foreground: 1.3 x 10^20 cm^-2
Excess significance: 2.8 sigma
Photon index:	     2.08 (+0.15, -0.14)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00932742.

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