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GCN Circular 13009

GRB 120305A: Swift-XRT refined Analysis
2012-03-06T08:03:06Z (12 years ago)
Phil Evans at U of Leicester <>
K.L. Page (U. Leicester), C. Pagani (U. Leicester), V. D'Elia (ASDC),
A. Maselli  (INAF-IASFPA), V. Mangano (INAF-IASFPA), M.C. Stroh (PSU),
D.N. Burrows (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester)
and G. Stratta report on behalf of the Swift-XRT team:

We have analysed 8.2 ks of XRT data for GRB 120305A (Stratta  et al.
GCN Circ. 13004), from 69 s to 24.9 ks after the  BAT trigger. The data
comprise 85 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 13008).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=2.66 (+0.22, -0.19).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.94 (+0.21, -0.20). The
best-fitting absorption column is  4.7 (+1.1, -0.9) x 10^21 cm^-2, in
excess of the Galactic value of 1.1 x 10^21 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.5 x 10^-11 (7.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     4.7 (+1.1, -0.9) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: 6.4 sigma
Photon index:	     1.94 (+0.21, -0.20)

The results of the XRT-team automatic analysis are available at

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