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GCN Circular 16256

Subject
GRB 140512A: Swift-XRT refined Analysis
Date
2014-05-13T07:56:04Z (10 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), V. D'Elia
(ASDC), M. de Pasquale (INAF-IASFPA), A. Maselli  (INAF-IASFPA), V.
Mangano (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), J.P. Osborne (U.
Leicester) and C. Pagani report on behalf of the Swift-XRT team:

We have analysed 6.1 ks of XRT data for GRB 140512A (Pagani  et al. GCN
Circ. 16249),  from 87 s to 12.6 ks after the  BAT trigger. The data
comprise 841 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. 

The late-time light curve (from T0+4.6 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.06 (+/-0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.460 (+0.029, -0.016). The
best-fitting absorption column is  consistent with the Galactic value
of 1.5 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.80 (+/-0.07) and a best-fitting absorption column
of 2.02 (+0.28, -0.26) x 10^21 cm^-2. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.0 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.02 (+0.28, -0.26) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 3.4 sigma
Photon index:	     1.80 (+/-0.07)

If the light curve continues to decay with a power-law decay index of
1.06, the count rate at T+24 hours will be 0.15 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x
10^-12 (7.4 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/00598819.

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