GCN Circular 15292

K.L. Page (U. Leicester), C. Pagani (U. Leicester), B. Sbarufatti
(INAF-OAB/PSU), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), M.C. Stroh
(PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), A.P. Beardmore (U.
Leicester) and	report on behalf of the Swift-XRT team: report on
behalf of the Swift-XRT team:

We have analysed 6.5 ks of XRT data for GRB 131002A,  from 56 s to 29.9
ks after the  BAT trigger. The data comprise 44 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+5.1 ks) can be modelled with  a
power-law decay with a decay index of alpha=1.05 (+0.26, -0.24).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.03 (+0.19, -0.18). The
best-fitting absorption column is  1.0 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 5.6 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 (4.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.0 (+0.5, -0.4) x 10^21 cm^-2
Galactic foreground: 5.6 x 10^20 cm^-2
Excess significance: 1.9 sigma
Photon index:	     2.03 (+0.19, -0.18)

If the light curve continues to decay with a power-law decay index of
1.05, the count rate at T+24 hours will be 7.7 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x
10^-13 (3.6 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/00572721.

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