Silicon X-ray absorption in the Galactic ISM: the gaseous component
  We present a detailed analysis of the gaseous component of the Si K edge
using high-resolution Chandra spectra of low-mass X-ray binaries. We fit the
spectra with amodified version of the ISMabs model, including new
photoabsorption cross sectionscomputed for all Si ionic species. We estimate
column densities for Si i, Si ii, Si iii, Si xii and Si xiii, which trace the
warm, intermediate temperature and hot phases of the Galactic interstellar
medium. We find that the ionic fractions of the first two phases are similar.
This may be due to the physical state of the plasma determined by the
temperature or to the presence of absorber material in the close vicinity of
the sources. Our findings highlight the need for accurate modeling of the
gaseous component before attempting to address the solid component.
