Structure and evolution of rotationally and tidally distorted stars

TL;DR

This study models the configuration and evolution of stars in binary systems considering rotational and tidal distortions, revealing how these effects influence stellar structure, luminosity, and mass ejection processes.

Contribution

It introduces a detailed model of distorted binary stars incorporating second-degree harmonic potentials, accretion luminosity, and stellar equilibrium equations.

Findings

Distortion increases with system evolution and time.

Luminosity in rotating stars is slightly weaker than in non-rotating stars.

Tidal effects enhance polar ejection and may promote equatorial ring ejection.

Abstract

This paper aims to study the configuration of two components caused by rotational and tidal distortions in the model of a binary system. The potentials of the two distorted components can be approximated to 2nd-degree harmonics. Furthermore, both the accretion luminosity ($\sigma_{i}$) and the irradiative luminosity are included in stellar structure equations. The equilibrium structure of rotationally and tidally distorted star is exactly a triaxial ellipsoids. A formula describing the isobars is presented, and the rotational velocity and the gravitational acceleration at the primary surface simulated. The results show the distortion at the outer layers of the primary increases with temporal variation and system evolution. Besides, it was observed that the luminosity accretion is unstable, and the curve of the energy-generation rate fluctuates after the main sequence in rotation sequences. The luminosity in rotation sequences is slightly weaker than that in non-rotation sequences. As a result, the volume expands slowly. Polar ejection is intensified by the tidal effect. The ejection of an equatorial ring may be favoured by both the opacity effect and the $g_{e}(\theta,\varphi)$-effect in the binary system.