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GCN Circular 16961

Subject
GRB 141026A: Swift-XRT refined Analysis
Date
2014-10-26T17:51:04Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
V. D'Elia (ASDC), M. de Pasquale (INAF-IASFPA), D.N. Burrows (PSU),
J.A. Kennea (PSU), V. Mangano (PSU), P.A. Evans (U. Leicester), B.P.
Gompertz (U. Leicester), J.P. Osborne (U. Leicester), A. Maselli 
(INAF-IASFPA) and L.M.Z. Hagen report on behalf of the Swift-XRT team:

We have analysed 10 ks of XRT data for GRB 141026A (Hagen  et al. GCN
Circ. 16950),  from 160 s to 46.2 ks after the	BAT trigger. The data
comprise 49 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Beardmore et al. (GCN Circ. 16956).

The late-time light curve (from T0+3.5 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.35 (+0.11, -0.12).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.07 (+0.09, -0.08). The
best-fitting absorption column is  4.9 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.92 (+0.28, -0.26)
and a best-fitting absorption column of 2.8 (+1.2, -1.0) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.8 x 10^-11 (5.4 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.8 (+1.2, -1.0) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: 2.0 sigma
Photon index:	     1.92 (+0.28, -0.26)

If the light curve continues to decay with a power-law decay index of
0.35, the count rate at T+24 hours will be 0.023 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.9 x
10^-13 (1.2 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00616502.

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