[vsnet-grb-info 21584] GRB 190114A: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23683
SUBJECT: GRB 190114A: Swift-XRT refined Analysis
DATE:    19/01/14 11:21:34 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A.
Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.P.
Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester) and S.J. LaPorte report on behalf of the Swift-XRT team:

We have analysed 6.8 ks of XRT data for GRB 190114A (LaPorte et al. GCN
Circ. 23677), from 235 s to 19.0 ks after the  BAT trigger. The data
comprise 64 s 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 Evans et
al. (GCN Circ. 23679).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=7.87 (+0.13, -0.43). At T+403 s  the decay
flattens to an alpha of 0.01 (+0.20, -0.17) before breaking again at
T+2398 s to a final decay with index alpha=1.16 (+/-0.14).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.38 (+0.17, -0.12). The
best-fitting absorption column is  1 (+13, -1) x 10^21 cm^-2, at a
redshift of 3.3765, in addition to the Galactic value of 1.6 x 10^21
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.80 (+0.09, -0.08) and a best-fitting absorption column of 2 (+10,
-2) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 3.9 x 10^-11 (4.8 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.6 x 10^21 cm^-2
Intrinsic column:    2 (+10, -2) x 10^21 cm^-2 at z=3.3765
Photon index:	     1.80 (+0.09, -0.08)

If the light curve continues to decay with a power-law decay index of
1.16, the count rate at T+24 hours will be 0.013 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.0 x
10^-13 (6.2 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00883600.

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