GCN Circular 15798

A. Maselli (INAF-IASFPA), A. Y. Lien (NASA/GSFC/ORAU) and P. A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

We have analysed 14 ks of XRT data for GRB 140206A (Lien et al. GCN
Circ. 15784
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 ), from 33 s to 30.2 ks after the BAT trigger. The data
comprise 1.2 ks in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 15793
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 ).

The light curve shows initial flaring activity with two flares peaking
at about 61 s and 223 s after the trigger. The underlying emission can
be modelled with a broken power-law decay: a flat decay with an index
alpha=0.756 (+0.026, -0.028), a break at T+10.7 ks and a late-time
decay with an index 1.31 (+0.15, -0.12).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.762 (+/-0.028). The
best-fitting absorption column is 1.25 (+/-0.07) x 10^21 cm^-2, in
excess of the Galactic value of 4.8 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 1.95 (+0.08, -0.07)
and a best-fitting absorption column of 1.22 (+0.19, -0.18) x 10^21
cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.8 x 10^-11 (4.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.22 (+0.19, -0.18) x 10^21 cm^-2
Galactic foreground: 4.8 x 10^20 cm^-2
Excess significance: 6.6 sigma
Photon index:	     1.95 (+0.08, -0.07)

If the light curve continues to decay with a power-law decay index of
1.31, the count rate at T+24 hours will be 0.088 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.3 x
10^-12 (4.3 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00585834.

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