Suzaku observation of IGR J16318-4848

TL;DR

This paper presents the first Suzaku X-ray observation of IGR J16318-4848, revealing its highly absorbed spectrum, fluorescent emission lines, and variability, contributing to understanding the nature of extreme absorbed X-ray binaries.

Contribution

First Suzaku observation providing detailed spectral analysis of IGR J16318-4848, highlighting its non-spherical absorber and spectral features.

Findings

Highly absorbed power law spectrum with cutoff at 20.5 keV

Detection of Fe and Ni fluorescent lines without Compton shoulder

Significant variability on hourly timescales

Abstract

We report on the first Suzaku observation of IGR J16318-4848, the most extreme example of a new group of highly absorbed X-ray binaries that have recently been discovered by the International Gamma-Ray Astrophysics Laboratory INTEGRAL. The Suzaku observation was carried out between 2006 August 14 and 17, with a net exposure time of 97 ks. The average X-ray spectrum of the source can be well described with a continuum model typical for neutron stars i.e., a strongly absorbed power law continuum with a photon index of 0.676(42) and an exponential cutoff at 20.5(6) keV. The absorbing column is 1.95(3)x10e24 cm-2. Consistent with earlier work, strong fluorescent emission lines of Fe Kalpha, Fe Kbeta, and Ni Kalpha are observed. Despite the large absorbing column, no Compton shoulder is seen in the lines, arguing for a non-spherical and inhomogeneous absorber. Seen at an average 5-60 keV absorbed flux of 3.4x10e-10 erg cm-2 s-1, the source exhibits significant variability on timescales of hours.