Detailed opacity calculations for astrophysical applications

Abstract

Nowadays, several opacity codes are able to provide data for stellar structure models, but the computed opacities may show significant differences. In this work, we present state-of-the-art precise spectral opacity calculations, illustrated by stellar applications. The essential role of laboratory experiments to check the quality of the computed data is underlined. We review some X-ray and XUV laser and Z-pinch photo-absorption measurements as well as X-ray emission spectroscopy experiments involving hot dense plasmas produced by ultra-high-intensity laser irradiation. The measured spectra are systematically compared with the fine-structure opacity code SCO-RCG. Focus is put on iron, due to its crucial role in understanding asteroseismic observations of $\beta$ Cephei-type and Slowly Pulsating B stars, as well as of the Sun. For instance, in $\beta$ Cephei-type stars, the iron-group opacity peak excites acoustic modes through the "kappa-mechanism". A particular attention is paid to the higher-than-predicted iron opacity measured at the Sandia Z-machine at solar interior conditions. We discuss some theoretical aspects such as density effects, photo-ionization, autoionization or the "filling-the-gap" effect of highly excited states.

submitted to "Atoms"

References in corpus (14)

• Helioseismology and Solar Abundances
• A New Generation of Los Alamos Opacity Tables
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• Photoionization of astrophysically relevant atomic ions at PIPE
• Plasma opacity calculations using the Starrett and Saumon average-atom model with ion correlations
• An Expanded Set of Los Alamos OPLIB Tables in MESA: Type-1 Rosseland-mean Opacities and Solar Models
• A quantitative study of some sources of uncertainty in opacity measurements
• The number of populated electronic configurations in a hot dense plasma
• A $\nu$ look at the Sun: Probing the conditions of the solar core using ${}^8$B neutrinos
• Towards solar measurements of nuclear reaction rates