Recently, the Stellar Physics Group of Yunnan Observatories, Chinese Academy of Sciences, has made progress in the research of asteroseismology of solar-like stars. The research was carried out by master's student WANG Shuai and Associate Researcher ZHANG Qiansheng, and the research findings were published in Research in Astronomy and Astrophysics (RAA). The study utilized Kepler asteroseismic data to constrain stellar parameters of a group of solar-like main sequence stars and investigate their element diffusion properties.

Asteroseismology is the scientific study that uses the properties of stellar oscillations to probe the internal structure of stars. By comparing the frequencies of stellar models with observed frequencies, fundamental stellar parameters such as mass, radius, and age can be obtained. It also helps to constrain physical processes in stellar interior, such as convective overshooting and diffusion.

They constructed stellar evolution models and oscillation databases for stars with 0.9 to 1.4 solar masses with and without element. By fitting the observed frequencies of 16 stars using the database, they rapidly obtained their stellar parameters. The most interesting result is the initial helium abundance of the stars. Without considering diffusion, the majority of target stars have initial helium abundances lower than the primordial helium abundance from Big Bang nucleosynthesis. However, when considering diffusion, the initial helium abundance significantly increases, resolving this issue. Furthermore, the oscillation frequencies of the best-fitting stellar models, considering diffusion, generally match the observations better than the case without diffusion. This demonstrates the importance of element diffusion in models of solar-like stars.

Element diffusion in stars depends on complex microphysical processes, and the current theoretical models are still incomplete. This study also investigated the intensity of element diffusion in stars by analyzing the second differences of p-mode oscillations, which are highly sensitive to element diffusion. They found that the observed second difference signals were significantly stronger than predicted by theoretical models, indicating that the current model underestimates the actual effects of element diffusion.

This work is co-sponsored by the National Key R&D Program of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Natural Science Foundation of China, the Danish National Research Foundation, the Foundation of the Chinese Academy of Sciences (Light of West China Program and Youth Innovation Promotion Association), and the Yunnan Ten Thousand Talents Plan Young & Elite Talents Project.

Contact: 
ZHANG Qiansheng 
Yunnan Observatories, CAS
Email: zqs@ynao.ac.cn