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Author Rogers, F. J. ♦ Swenson, F. J. ♦ Iglesias, C. A.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PHYSICS ♦ OPACITY ♦ ANALYTICAL SOLUTION ♦ STAR MODELS ♦ EQUATIONS OF STATE ♦ NUMERICAL SOLUTION ♦ STARS ♦ ENTROPY ♦ ASTROPHYSICS ♦ COULOMB FIELD ♦ PLASMA ♦ STAR EVOLUTION ♦ ELEMENT ABUNDANCE ♦ IONIZATION ♦ PARTITION FUNCTIONS ♦ STELLAR INTERIORS ♦ INTERNAL ENERGY
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 {approximately}0.8 {ital M}{sub {circle_dot}}. An interpolation code is provided along with the tables to facilitate their use. {copyright} {ital 1996 The American Astronomical Society.}
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-01-01
Publisher Department Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publisher Place United States
Journal Astrophysical Journal
Volume Number 456
Issue Number 2
Organization Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)


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