On the importance of inner-shell transitions for opacity calculations

For high temperatures and densities, stellar opacities obtained from the Opacity Project (OP) were smaller than those obtained from the OPAL project. Iglesias and Rogers (1995 Astrophys. J. 443 469) suggested that the discrepancy was due to the omission by OP of important atomic inner-shell processes, and considered in detail results for a mixture of six elements: H, He, C, 0, S and Fe. Extensive new inner-shell data have now been computed using the code AUTOSTRUCTURE. It is shown that the inclusion of these data in the OP work gives opacities for the six-element mix which are in much closer agreement with those from OPAL. We also discuss a number of problems relating to the calculation of opacities and of equations of state for dense plasmas.