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GCN Circular 9711

Subject
GRB 090726: Swift-XRT Team refined analysis
Date
2009-07-27T13:30:11Z (15 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team:

We have analysed the first five orbits of data collected for GRB 090726, 
comprising 9.4 ks between 3.6 and 28 ks after the trigger, all in Photon 
Counting mode. The enhanced XRT position for this burst was given by Evans 
et al. in GCN Circ. 9710.

The X-ray light-curve can be modelled with a single power-law with a decay 
index of alpha = 1.29 +/- 0.12.

A spectrum formed from these PC data can be fitted with an absorbed 
power-law of Gamma = 2.50 +0.26/-0.24 and a total absorbing column of NH = 
(1.2 +/- 0.5) x 10^21 cm^-2, which is in excess of the Galactic value 
(3.83 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 3.1 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1.

If the light-curve continues to decay with alpha ~ 1.29, the predicted 
count rate at 24 hours is 3.4 x 10^-3 count s^-1, corresponding to an 
observed (unabsorbed) flux of 1.1 x 10^-13 (1.7 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/00358422.

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