Structure and evolution of rotationally and tidally distorted stars

Free access article

Issue		A&A Volume 504, Number 1, September II 2009


Page(s)		161 - 170
Section		Stellar structure and evolution
DOI		http://dx.doi.org/10.1051/0004-6361/200811144
Published online		09 July 2009

A&A 504, 161-170 (2009)
DOI: 10.1051/0004-6361/200811144

Structure and evolution of rotationally and tidally distorted stars

H. F. Song^{1, 2}, Z. Zhong¹, and Y. Lu¹

¹ College of science, Guizhou University, Guiyang, 550025, PR China
e-mail: sci.hfsong@gzu.edu.cn; zhongzhen307@yahoo.cn
² Joint Centre for Astronomy, National Astronomical Observatories-Guizhou University, Guiyang, 550025, PR China
e-mail: songhanfeng@163.com

Received 14 October 2008 / Accepted 2 June 2009

Abstract
Aims. This paper aims to study the configuration of two components caused by rotational and tidal distortions in the model of a binary system.
Methods. 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.
Results. 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 $g_{\rm e}(\theta,\varphi)$ -effect in the binary system.

Key words: stars: rotation -- stars: binaries: close

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