The X-Ray Photo-ionized Wind in Cen X-3/V779 Cen

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 using spectral models of recombination in an X-ray photoionized wind. We test models where the wind comes from the companion star and also models where the wind comes from the accretion disk and find that the wind in the system cannot be dominated by an accretion disk wind. The parameters which we derive for the companion star wind, especially the mass-loss rate divided by the terminal velocity, are consistent with the UV radiation driven winds of isolated O stars. This is surprising as the normal radiation driving mechanism cannot work in highly X-ray photonized plasma. We have also observed Cen X-3 in eclipse with Chandra. The line flux ratios in helium-like triplets confirm our interpretation that the emission lines are due to recombination in a photoionized plasma. Preliminary results suggest that the velocity of the wind derived from line shifts and line widths is lower than that of winds in isolated O stars and so the mass-loss rate is also less than that for isolated O stars. 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.