TITLE:   GCN CIRCULAR
NUMBER:  16128
SUBJECT: GRB 140419A: Swift-XRT refined Analysis
DATE:    14/04/19 17:31:39 GMT
FROM:    Alessandro Maselli at INAF/IASF Palermo  <maselli@ifc.inaf.it>

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), 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).

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.