Asteroseismology of solar-type stars: signatures of convective and/or helium cores

Abstract

Asteroseismology of solar-type stars is an important tool for constraining stellar parameters and internal structure. Several frequency combinations are largely used for comparisons between models and observations. In particular, the ``small separations'' are very sensitive to stellar cores. We showed in a previous paper that they can change sign, in contradiction with the ``asymptotic theory'', and that this behaviour could correspond to signatures of convective and/or helium cores. Here we analyse this behaviour in detail by systematic modelling during stellar evolution. We computed evolutionary tracks for models with various masses (from 1.05 to 1.25 Msun) and various chemical composition, with and without overshooting. We computed the adiabatic oscillation frequencies of the models and analysed the evolution of their small separations along an evolutionary track. We found that, for all cases, the stars go through a stage, during their evolution time, where the small separations computed between degrees l=0 and l=2 become negative in the observed range of frequencies. This behaviour is clearly related to the signature of a helium-rich core. We discuss the consequences for the interpretation of the acoustic frequencies observed in solar-type stars.

arXiv comment14 pages, 10 figures, accepted for publication in A&A

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Cited by in corpus (6)

• Effects of Uniform and Differential Rotation on Stellar Pulsations
• Modelling the Autocovariance of the Power Spectrum of a Solar-Type Oscillator
• Precise Modeling of the Exoplanet Host Star and CoRoT Main Target HD 52265
• New seismic analysis of the exoplanet-host star Mu Arae
• The Solar and $\alpha$ Centauri A and B models improved by opacity enhancement - a possible explanation for the oversize cool stars
• What do stars tell us about planets? Asteroseismology of exoplanet-host stars