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GCN Circular 14649

Subject
GRB 130514A: Swift-XRT refined Analysis
Date
2013-05-15T01:30:03Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
B.P. Gompertz (U. Leicester), A. Maselli  (INAF-IASFPA), V. Mangano
(INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU), J.A. Kennea
(PSU), M.C. Stroh (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester) and E. Sonbas report on behalf of the Swift-XRT team:

We have analysed 8.5 ks of XRT data for GRB 130514A (Sonbas  et al. GCN
Circ. 14632),  from 95 s to 37.1 ks after the  BAT trigger. The data
comprise 405 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 14637).

The late-time light curve (from T0+5.8 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.15 (+0.13, -0.12).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.82 (+/-0.03). The
best-fitting absorption column is  3.14 (+0.13, -0.12) x 10^21 cm^-2,
in excess of the Galactic value of 7.6 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 1.99 (+0.20, -0.19)
and a best-fitting absorption column of 1.4 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.7 x 10^-11 (5.0 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.4 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 7.6 x 10^20 cm^-2
Excess significance: 2.1 sigma
Photon index:	     1.99 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
1.15, the count rate at T+24 hours will be 9.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.4 x
10^-13 (4.5 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00555821.

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