GCN Circular 15296

M.C. Stroh and B. Sbarufatti report on behalf of the Swift-XRT team:

We have analysed 1.8 ks of XRT data for GRB 131002B,  from 58 s to 6.5
ks after the  BAT trigger. The data comprise 282 s in Windowed Timing
(WT) mode with the remainder in Photon Counting (PC) mode. 

The light curve consists of a relatively flat region of WT data from
T+58 to T+333 s with a count rate ranging between 10 and 50 cts/s. The
WT observation ended when Swift entered the SAA. PC data exists from
T+5.0 to T+6.5 ks with a count rates between 0.1 and 0.04 cts/s. Since
there is only 1.8ks of data on this source, it is difficult to be
confident that a fit to these data points truly models the overall
behavior in this GRB.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.46 (+0.04, -0.03). The
best-fitting absorption column is  consistent with the Galactic value
of 9.1 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 4.7 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Galactic foreground: 9.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.46 (+0.04, -0.03)

If the light curve continues to decay with a power-law decay index of
2.05, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.2 x
10^-15 (1.0 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00572742.

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