Effects of rotational mixing on the asteroseismic properties of solar-type stars

TL;DR

This study investigates how rotational mixing influences the evolution and asteroseismic characteristics of solar-type stars, revealing significant effects on their structure, chemical composition, and observable seismic parameters.

Contribution

It provides new insights into the impact of rotational mixing and magnetic fields on stellar evolution and seismic properties of solar-type stars.

Findings

Rotational mixing increases effective temperature and shifts evolutionary tracks to the blue.

Rotating models show higher large frequency separations at the same evolutionary stage.

Magnetic fields reduce the efficiency of rotational mixing in solar-type stars.

Abstract

The influence of rotational mixing on the evolution and asteroseismic properties of solar-type stars is studied. Rotational mixing changes the global properties of a solar-type star with a significant increase of the effective temperature resulting in a shift of the evolutionary track to the blue part of the HR diagram. These differences are related to changes of the chemical composition, because rotational mixing counteracts the effects of atomic diffusion leading to larger helium surface abundances for rotating models than for non-rotating ones. Higher values of the large frequency separation are then found for rotating models than for non-rotating ones at the same evolutionary stage, because the increase of the effective temperature leads to a smaller radius and hence to an increase of the stellar mean density. Rotational mixing also has a considerable impact on the structure and chemical composition of the central stellar layers by bringing fresh hydrogen fuel to the core, thereby enhancing the main-sequence lifetime. The increase of the central hydrogen abundance together with the change of the chemical profiles in the central layers result in a significant increase of the values of the small frequency separations and of the ratio of the small to large separations for models including shellular rotation. This increase is clearly seen for models with the same age sharing the same initial parameters except for the inclusion of rotation as well as for models with the same global stellar parameters and in particular the same location in the HR diagram. By computing rotating models of solar-type stars including the effects of a dynamo that possibly occurs in the radiative zone, we find that the efficiency of rotational mixing is strongly reduced when the effects of magnetic fields are taken into account, in contrast to what happens in massive stars.