Brief history of SAHA-S
SAHA-S is an equation of state (EOS) for astrophysical plasma developed primarily for the Sun and solar-type stars. Its authors are V.K. Gryaznov, I.L. Iosilevskiy, A.N. Starostin and V.E. Fortov. SAHA-S is developed in the framework of chemical picture but includes Coulomb contributions from the physical picture.
The first version appeared in early 2000; the first publication is dated 2004. Next version was calculated in 2011 and named SAHA-S version 3. It takes into account ionization transition, Coulomb correction, electron degeneracy, relativistic effects. In addition to hydrogen and helium, eight heavy elements are included in computations: C, N, O, Ne, Mg, Si, S, Fe. EOS includes all ions of these elements and many molecules. The total mass fraction of Z of the heavy elements is varied from 0.0 to 0.02; only one set of relative abundances of elements was computed. SAHA-S version 3 has been incorporated in several stellar evolution codes: HPCSE (SAI MSU, Russia), CESAM2k and CESTAM (France), CLES (Belgium).
The revised and updated version 7 of SAHA-S was released in the middle of 2019. Physical and numerical algorithms have been improved. Particular attention is given to an effect of relative abundances of heavy elements. The EOS tables are computed for three mixtures of relative abundances: AGSS09, GN93, and OPAL EOS mixture.
More details about SAHA-S and its applications can be found in papers presented on tab “References” and in documentation supplied with the EOS tables.