GCN Circular 16128

A. Maselli, M. De Pasquale (INAF-IASFPA), P. A. Evans (U Leicester) and
F. E. Marshall (NASA/GSFC) report on behalf of the Swift-XRT team:

We have analysed 10 ks of XRT data for GRB 140419A (Marshall et al. GCN
Circ. 16118
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 ), from 79 s to 24.3 ks after the BAT trigger. The data
comprise 849 s in Windowed Timing (WT) mode (the first 5 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. 16124
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 ).

The late-time light curve (from T0+5.4 ks) can be modelled with a
power-law decay with a decay index of alpha=1.29 (+/-0.07).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.803 (+0.029, -0.028). The
best-fitting absorption column is 1.7 (+2.8, -1.7) x 10^21 cm^-2, at a
redshift of 3.956, in addition to the Galactic value of 3.9 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.83 (+/-0.06) and a best-fitting absorption column of 1.2 (+/-0.6)
x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.0 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 3.9 x 10^20 cm^-2
Intrinsic column:    1.2 (+/-0.6) x 10^22 cm^-2 at z=3.956
Photon index:	     1.83 (+/-0.06)

If the light curve continues to decay with a power-law decay index of
1.29, the count rate at T+24 hours will be 0.042 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x
10^-12 (1.7 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/00596426.

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