Influence of Projection Operator on Oxygen Line Shapes and its effect on Rosseland-Mean Opacity in Stellar Interiors
Abstract
The Rosseland-Mean opacity (RMO) is an important quantity in determining radiation transport through stars. The solar-convection-zone boundary predicted by the standard solar model disagrees with helioseismology measurements by many sigma; a 14% increase in the RMO would resolve this discrepancy. Experiments at Sandia National Laboratories are now measuring iron opacity at solar-interior conditions, and significant discrepancies are already observed. Highly-ionized oxygen is one of the dominant contributions to the RMO. The strongest line, Lyman alpha, is at the peak of the Rosseland weighting function. The accuracy of line-broadening calculations has been called into question due to various experimental results and comparisons between theory. We have developed an ab-initio calculation to explore different physical effects, our current focus is treating penetrating collisions explicitly. The equation of motion used to calculate line shapes within the relaxation and unified theories includes a projection operator, which performs an average over plasma electron states; this is neglected due to past calculations approximate treatment of penetrations. We now include this projection term explicitly, which results in a significant broadening of spectral lines from highly-charged ions (low-Z elements are not much affected). The additional broadening raises the O Ly-alpha wing opacity by a factor of 5; we examine the consequences of this additional broadening on the Rosseland mean.
- Publication:
-
American Astronomical Society Meeting Abstracts #231
- Pub Date:
- January 2018
- Bibcode:
- 2018AAS...23145202G