The properties of the absorbing and line-emitting material in IGR J16318 - 4848

Abstract

We have performed a detailed analysis of the XMM-Newton observation of IGR J16318-4848, to study the properties of the matter responsible for the obscuration and for the emission of Fe and Ni lines. Even if the line-of-sight material has a column density of about 2 × 1024 cm -2, from the Fe Kα line EW and Compton Shoulder we argue that the matter should have an average column density of a few × 10 23 cm-2, along with a covering factor of about 0.1-0.2. The iron Kα line varies on time-scales as short as 1000 s, implying a size of the emitting region smaller than about 3 × 1013 cm. The flux of the line roughly follows the variations of the continuum, but not exactly, suggesting a variation of the geometrical properties of the emitting region on similar time-scales.