RADIATIVE OPACITIES FOR CARBON-RICH AND OXYGEN-RICH MIXTURES

Recent OPAL calculations have obtained significant differences in the Rosseland mean opacities compared with earlier Los Alamos work. These new opacities have had a favorable impact on several astrophysical pro blems, but the efforts have concentrated on hydrogen main-sequence sta rs or stellar envelopes. The present calculations consider carbon- and oxygen-rich mixtures. It is shown that for such mixtures the Coulomb corrections beyond the weak-coupling approximation are not negligible in the ionization-balance calculations when Rosseland mean opacities a re computed. As for hydrogen-rich compositions, the hydrogen-depleted mixtures can show factors of 2-3 enhancements in the opacity compared with the Los Alamos results at temperatures of a few hundred thousand degrees. For temperatures above a million degrees there are opacity in creases as well as decreases of approximately 20%, depending on densit y. Tables of Rosseland mean opacities are provided that allow accurate interpolation for compositions of arbitrary amounts of hydrogen, carb on, and oxygen.