Suzaku observation of IGR J16318-4848

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 (X²ᵣₑd = 0.99) 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 NH = 1.95(3) x 10²⁴ cm⁻². Consistent with earlier work, strong fluorescent emission lines of Fe Kα , Fe Kβ , and Ni Kα are observed. Despite the large NH, 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 3.4 x 10⁻¹⁰ erg cm⁻² s⁻¹, the source exhibits significant variability on timescales of hours.