Iron lines in X-ray spectra of high mass X-ray binaries

Abstract

Observations of high mass X-ray binaries with EXOSAT have shown that the X-ray spectra can be modeled with absorption by a gas stream from the primary trailing the neutron star. The dense gas stream highly absorbs the direct X-rays from the neutron star at orbital phases when the line of sight passes through the gas stream. A second, low-absorption component becomes visible which can be explained by Thomson scattering of X-rays around the dense gas stream. The spectra of GX301-2 show an iron emission line near 6.4 keV with a wide range of line intensities. Adding the iron line to the low-absorption component of the spectrum the derived Fe column densities to explain the line intensity are consistent with the equivalent H column densities causing the photo-electric absorption of the low-absorption component.