GCN Circular 32651
Subject
GRB 221009A: Swift-XRT refined Analysis
Date
2022-10-10T11:19:36Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A.
Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB),
D.N. Burrows (PSU) and E Bissaldi report on behalf of the Swift-XRT
team:
We have analysed 12 ks of XRT data for GRB 221009A (E Bissaldi et al.
GCN Circ. 32637), from 159 s to 58.4 ks after the BAT trigger. The
data are entirely in Windowed Timing (WT) mode (the first 10 s were
taken while Swift was slewing). A spectrum formed from the WT mode data
can be fitted with an absorbed power-law with a photon spectral index
of 1.836 (+0.012, -0.011). The best-fitting absorption column is 6.76
(+/-0.16) x 10^21 cm^-2, at a redshift of 0.151, in addition to the
Galactic value of 5.4 x 10^21 cm^-2 (Willingale et al. 2013). The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 5.7 x 10^-11 (1.0 x 10^-10) erg cm^-2
count^-1.
A summary of the WT-mode spectrum is thus:
Galactic foreground: 5.4 x 10^21 cm^-2
Intrinsic column: 6.76 (+/-0.16) x 10^21 cm^-2 at z=0.151
Photon index: 1.836 (+0.012, -0.011)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01126853.
This circular is an official product of the Swift-XRT team.