An Explanation of Observed Trends in the X-ray Emission from Single Wolf-Rayet Stars.

The O and early B star winds show empirical corre- lations between X-ray (Lx) and Bolometric (LBol) luminosity as well as wind properties such as wind momentum and wind kinetic energy. Wolf-Rayet stars do not. We discuss scaling rela- tions to qualitatively explain this lack of correlation among the WR winds and to quantitatively reproduce the observed ratio of X-ray luminosities between the N-rich WN types and C-rich WC types. If (a) the filling factor of hot X-ray emitting gas varies as ( u M/v1) 1 for stars of different mass loss and terminal speed and (b) the ambient Wolf-Rayet wind component is optically thick to the hot gas X-rays, then a lack of correlation between Lx and wind parameters is to be expected. The emergent X-ray emission then depends only on factors relating to relative abun- dances and ionization. The observed ratio LX(WN)/LX(WC) is consistent with our scaling analysis using typical WN and WC abundances.