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Emulating the OPAL equation of state

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Abstract

The equation of state for the structure of the Sun and stars has to be precise to allow comparisons with observations, i.e., helioseismic inversions of thermodynamic quantities. Among the two of the most popular formalisms are (1) the OPAL equation of state developed at Livermore and (2) the Mihalas-Hummer-Däppen (MHD) equation of state. While OPAL has a solid theoretical foundation, and matches the observational data better, the MHD formalism is more intuitive, easy to realize, and has the possibility of adjustable parameters. Furthermore, it an open-source product in contrast to the proprietary OPAL. Recently a version of MHD has been obtained by including the so-called “Plank-Larkin partition function” and by adding scattering-state terms. The resulting formalism matches OPAL rather well. Here, we report on the next logical step, the implementation of this MHD upgrade into the simple and popular CEFF equation of state. Such an implementation will make it a flexible and convenient tool, allowing an approximative on-line implementation of OPAL in solar and stellar models.

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Authors and Affiliations

  1. University of Southern California, Los Angeles, USA

    Hsiao-Hsuan Lin & Werner Däppen

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  1. Hsiao-Hsuan Lin
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  2. Werner Däppen
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Correspondence to Hsiao-Hsuan Lin.

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Lin, HH., Däppen, W. Emulating the OPAL equation of state. Astrophys Space Sci 328, 175–178 (2010). https://doi.org/10.1007/s10509-010-0264-7

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  • DOI: https://doi.org/10.1007/s10509-010-0264-7

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