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
Not found
 
 
), 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
Not found
 
 
).

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.