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GCN Circular 14040

Subject
GRB 121202A: Swift-XRT refined Analysis
Date
2012-12-02T18:41:45Z (11 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K.L. Page (U. Leicester) and S. R. Oates (UCL-MSSL) report on behalf of
the Swift-XRT team:

We have analysed 12 ks of XRT data for GRB 121202A (Oates  et al. GCN
Circ. 14032), from 2.8 ks to 31.9 ks after the	BAT trigger. The data
comprise 16 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Evans et al. (GCN. Circ 14038).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.66 (+/-0.08).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.08 (+/-0.15). The
best-fitting absorption column is  1.7 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 3.9 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 (5.3 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.7 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 3.9 x 10^20 cm^-2
Excess significance: 5.5 sigma
Photon index:	     2.08 (+/-0.15)

If the light curve continues to decay with a power-law decay index of
1.66, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.5 x
10^-14 (1.1 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/00540255.

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