GCN Circular 28850
Subject
GRB 201104B: Swift-XRT refined Analysis
Date
2020-11-06T09:09:44Z (4 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) and
B. Sbarufatti report on behalf of the Swift-XRT team:
We have analysed 4.9 ks of XRT data for GRB 201104B (Sbarufatti et al.
GCN Circ. 28825), from 105 s to 131.7 ks after the BAT trigger. The
data comprise 347 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 546 s of PC mode data and 3 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 =
5.21441, +7.84185 which is equivalent to:
RA (J2000): 00h 20m 51.46s
Dec(J2000): +07d 50' 30.7"
with an uncertainty of 2.3 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an
index of alpha=0.11 (+0.11, -0.12), followed by a break at T+338 s to
an alpha of 1.21 (+0.05, -0.04).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.80 (+/-0.07). The
best-fitting absorption column is 1.12 (+0.30, -0.28) x 10^22 cm^-2,
at a redshift of 1.954, in addition to the Galactic value of 5.7 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 WT-mode spectrum is thus:
Galactic foreground: 5.7 x 10^20 cm^-2
Intrinsic column: 1.12 (+0.30, -0.28) x 10^22 cm^-2 at z=1.954
Photon index: 1.80 (+/-0.07)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01004168.
This circular is an official product of the Swift-XRT team.