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GCN Circular 20050

Subject
GRB 161014A: Swift-XRT refined Analysis
Date
2016-10-15T14:31:20Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri
(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R.
Roegiers (PSU) and J.L. Racusin report on behalf of the Swift-XRT team:

We have analysed 5.5 ks of XRT data for GRB 161014A (Racusin et al. GCN
Circ. 20035), from 108 s to 34.8 ks after the  BAT trigger. The data
comprise 48 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. Using 5612 s of PC mode data and 8 UVOT images, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 332.64760, +7.46873
which is equivalent to:

RA (J2000): 22h 10m 35.42s
Dec(J2000): +07d 28' 07.4"

with an uncertainty of 1.4 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.45 (+/-0.12), followed by a break at T+1757 s to an
alpha of 1.59 (+0.14, -0.13).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.83 (+0.11, -0.10). The
best-fitting absorption column is  1.5 (+0.9, -0.8) x 10^22 cm^-2, at a
redshift of 2.823, in addition to the Galactic value of 7.5 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 3.7 x
10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 7.5 x 10^20 cm^-2
Intrinsic column:    1.5 (+0.9, -0.8) x 10^22 cm^-2 at z=2.823
Photon index:	     1.83 (+0.11, -0.10)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00717500.

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