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Astron. Astrophys. 326, 187-194

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Solar models: influence of equation of state and opacity

M. Yldz1 and N. Kzloglu2

1Ege University, Department of Astronomy and Space Sciences, Izmir 35100 , Turkey
2Middle East Technical University, Physics Department, Ankara 06531, Turkey

Received 18 September 1996 / Accepted 23 April 1997


Solar models through evolutionary phases of gravitational contraction, pre-main sequence and MS phases, up to current age FORMULA and FORMULA , were studied adopting different prescriptions for the equation of state (EOS) and different opacity tables.

Old EOS in Ezer's evolutionary code that we adopted in previous studies includes pressure ionization, and degeneracy of electrons. In the present study the EOS is obtained by minimization of the free energy (Mihalas et al. 1990, MHD), and the radiative opacity is derived from recent OPAL tables, implemented by the low temperature tables of Alexander & Ferguson. The results are compared with solar models we computed with different radiative opacities (Cox & Stewart 1970) and different EOS, as with models computed by other authors.

Finally we provide the internal run of the thermodynamic quantities of our preferred solar model which possesses the following characteristics: age FORMULA , initial He abundance by mass 0.285, parameter of the mixing length FORMULA , radius and temperature at the bottom of the convective envelope are FORMULA and FORMULA , respectively.

Key words: Sun: interior - solar evolution - equation of state

Send offprint requests to: M. Yildiz

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 20, 1998