X-Ray Recombination Line Spectral Modeling for Cen X-3

We fit the X-ray emission line spectrum of the Cen X-3 X-ray binary system obtained in and out of eclipse with ASCA. The emission lines are due to recombination in the wind of the companion star which is photo-ionized by the X-rays from the neutron star. The large X-ray luminosity of the neutron star would be expected to ionize the wind and destroy the ions which provide the opacity for the radiation-driven wind. However, we find that the best fit wind parameters agree very well with those of isolated stars of the same stellar type. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.