GCN Circular 24961
Subject
GRB 190701A: Swift-XRT refined Analysis
Date
2019-07-02T02:35:59Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
E. Ambrosi (INAF-IASFPA) , V. D'Elia (ASDC), D.N. Burrows (PSU), J. D.
Gropp (PSU), A. Tohuvavohu (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. D'Ai
(INAF-IASFPA) and T.N. Ukwatta report on behalf of the Swift-XRT team:
We have analysed 8.4 ks of XRT data for GRB 190701A (Ukwatta et al. GCN
Circ. 24934), from 144 s to 34.9 ks after the BAT trigger. The data
comprise 10 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Osborne et al. (GCN Circ. 24935).
The light curve can be modelled with an initial power-law decay with an
index of alpha=8.0 (+0.0, -0.9), followed by a break at T+239 s to an
alpha of 0.40 (+0.08, -0.09).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.81 (+0.23, -0.12). The
best-fitting absorption column is consistent with the Galactic value
of 6.4 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 4.7 x 10^-11 (7.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 6.4 (+/-1.0) x 10^21 cm^-2
Galactic foreground: 6.4 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.81 (+0.23, -0.12)
If the light curve continues to decay with a power-law decay index of
0.40, the count rate at T+24 hours will be 0.018 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.5 x
10^-13 (1.3 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/00912310.
This circular is an official product of the Swift-XRT team.