GCN Circular 15926
Subject
GRB 140304A: Swift-XRT refined Analysis
Date
2014-03-05T02:57:04Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), C. Pagani (U. Leicester), A. Maselli
(INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU),
J.A. Kennea (PSU), V. Mangano (PSU), M.C. Stroh (PSU), A.P. Beardmore
(U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.4 ks of XRT data for GRB 140304A (Evans et al. GCN
Circ. 15915), from 81 s to 23.1 ks after the BAT trigger. The data
comprise 42 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. 15925). The late-time light curve (from
T0+5.2 ks) is consistent with a constant source of mean count rate
1.1e+00 ct/sec. A power-law fit gives an index of 0.2 (+/-0.7).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.00 (+0.15, -0.14). The
best-fitting absorption column is 9.8 (+3.4, -3.1) x 10^20 cm^-2, in
excess of the Galactic value of 6.0 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.6 x 10^-11 (4.6 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 9.8 (+3.4, -3.1) x 10^20 cm^-2
Galactic foreground: 6.0 x 10^20 cm^-2
Excess significance: 2.0 sigma
Photon index: 2.00 (+0.15, -0.14)
If the light curve continues to decay with a power-law decay index of
0.2, the count rate at T+24 hours will be 0.024 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x
10^-13 (1.1 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/00590206.
This circular is an official product of the Swift-XRT team.