Asteroseismic study of helium and heavy element diffusion in solar-type stars

Free access article

Issue		A&A Volume 508, Number 2, December III 2009


Page(s)		849 - 854
Section		Stellar structure and evolution
DOI		http://dx.doi.org/10.1051/0004-6361/200912417
Published online		21 October 2009

A&A 508, 849-854 (2009)
DOI: 10.1051/0004-6361/200912417

Asteroseismic study of helium and heavy element diffusion in solar-type stars

N. Gai¹, S. L. Bi¹, Y. K. Tang², and L. H. Li³

¹ Department of Astronomy, Beijing Normal University, Beijing 100875, PR China
    e-mail: gaining@mail.bnu.edu.cn; bisl@bnu.edu.cn
² Department of Physics, Dezhou University, Dezhou 253023, PR China
    e-mail: tyk450@163.com
³ Department of Astronomy, Yale University, New Haven, CT06520, USA
    e-mail: li@astro.yale.edu

Received 3 May 2009 / Accepted 18 September 2009

Abstract
Aims. Element diffusion is a basic physical element transport mechanism which induces the redistribution of chemical elements. Using the asteroseismic method, we study the effects of helium and heavy element diffusion on the internal structure and stellar evolution of solar-type stars. We also provide asteroseismic parameters for a grid of models which would be useful for direct comparison with the Kepler mission observations.
Methods. We construct a grid of solar-type stellar models with various masses (from 0.8 $M_{\odot}$ to 1.2 $M_{\odot}$ ) and metallicities (Z_i = 0.03, 0.025, 0.02, 0.015, 0.01, 0.005) with and without helium and heavy element diffusion. We compute “second differences” and “small separations” of the solar-metallicity models (Z_i = 0.02) to analyze the effects of diffusion on the convection zone, helium abundance and the evolutionary sequence of the star. In order to study the asteroseismic property of models with and without diffusion, we compute the p-mode oscillation frequencies of low-degree modes for a grid of models and construct the $(\langle \Delta\nu_{0} \rangle, \langle d_{02} \rangle)$ asteroseismic diagram.
Results. We find that the element diffusion could speed up the evolution of the star, especially in the main sequence. The results show that it could enlarge the convective core and change the base of the convection envelope. In addition, the helium and heavy element diffusion make the models evolve to lower large and small separations in the asteroseismic diagram. This effect is more efficient at lower metallicity.

Key words: stars: evolution -- stars: interiors -- stars: oscillations

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.