The chemical composition and equation of state of the sun inferred from seismic models through an inversion procedure

Chia Hsien Lin, Werner Däppen

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The remarkable quality of present helioseismic data provides the possibility to investigate the microscopic physics of the solar interior. An inversion procedure to reveal the equation of state and chemical composition in the Sun has been developed. The method is based on using the discrepancy in the adiabatic gradient γ1 ≡ (∂ In P/∂ In ρ)s (s being the specific entropy) to infer the discrepancies in the equation of state and in the chemical composition between the Sun and solar models. Adequate accuracy and stability of the procedure have been demonstrated. Our inverted δγ11 between the Sun and model S of Christensen-Dalsgaard et al. is consistent with the earlier result obtained by Basu et al. We also found that the inverted δγ 11 between the Sun and an envelope model implemented with the so-called CEFF equation of state (Christensen-Dalsgaard & Däppen) basically shows two dips. The dips are located at 0.975 and 0.988 R. Both dips cannot be eliminated merely by tuning the helium abundance over a reasonable range; hence, it appears that the dips are a manifestation of inappropriate approximations used in the equation of state of the underlying models.

Original languageEnglish
Pages (from-to)556-570
Number of pages15
JournalAstrophysical Journal
Volume623
Issue number1 I
DOIs
StatePublished - 10 Apr 2005

Keywords

  • Equation of state
  • Stars: evolution
  • Sun: evolution
  • Sun: helioseismology
  • Sun: interior

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