OPAL Equation-of-State Tables for Astrophysical Applications

TLDR

OPAL opacities have resolved long‑standing discrepancies between theory and observation, and the OPAL approach differs from free‑energy minimization methods by naturally incorporating composite particles, many‑body effects, and subtle quantum corrections through a systematic Coulomb‑coupling expansion. The authors aim to provide the equation‑of‑state data that complements these successful OPAL opacity calculations. They construct the EOS via an activity expansion of the grand canonical partition function, naturally including composite particles and many‑body effects, and generate tables of pressure, internal energy, entropy, and derivatives over a wide range of stellar conditions, together with an interpolation code. The EOS predicts pressure ionization as a natural consequence of the theory. Published in The Astrophysical Journal (Jan 1996), DOI 10.1086/176705.

Abstract

view Abstract Citations (802) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OPAL Equation-of-State Tables for Astrophysical Applications Rogers, Forrest J. ; Swenson, Fritz J. ; Iglesias, Carlos A. Abstract OPAL opacities have recently helped to resolve a number of long-standing discrepancies between theory and observation. This success has made it important to provide the associated equation-of-state (EOS) data. The OPAL EOS is based on an activity expansion of the grand canonical partition function of the plasma in terms of its fundamental constituents (electrons and nuclei). The formation of composite particles and many- body effects on the internal bound states occur naturally in this approach. Hence, pressure ionization is a consequence of the theory. In contrast, commonly used approaches, all of which are based on minimization of free energy, are forced to assert the effect of the plasma on composite particles and must rely on an ad hoc treatment of pressure ionization. Another advantage of the OPAL approach is that it provides a systematic expansion in the Coulomb coupling parameter that includes subtle quantum effects generally not considered in other EOS calculations. Tables have been generated that provide pressure, internal energy, entropy, and a variety of derivative quantities. These tables cover a fairly broad range of conditions and compositions applicable to general stellar-evolution calculations for stars more massive than ∼0.8 Msun. An interpolation code is provided along with the tables to facilitate their use. Publication: The Astrophysical Journal Pub Date: January 1996 DOI: 10.1086/176705 Bibcode: 1996ApJ...456..902R Keywords: ATOMIC PROCESSES; EQUATION OF STATE; ATOMIC DATA full text sources ADS |