EQUILIBRIUM STRUCTURE AND OSCILLATIONS OF ROTATIONALLY AND TIDALLY DISTORTED GAS SPHERES

Abstract

In the present thesis we have primarily addressed ourselves to certain shortcomings noticed in the work of Mohan, Saxena and Agarwal (Astrophys. Space Sci., Vol.163, p.23,1990 and Vo1.178, p.89, 1991) which relates to the problems of computing the equilibrium structure and periods of oscillations of rotating stars and star in binary system. In this work equipotentials surfaces of the rotationally and tidally distorted primary component of a binary star are approximated by Roche equipotential surfaces which are obtained by assuming the whole mass of the star to be concentrated at its centre which acts as a point mass surrounded by an evanescent envelope in which density varies as the square of distance from the centre. Since even in this approximation analytic solutions in closed form are not possible, following Kopal (1972) series expansions have been to represent the potential on an equipotentials surface. Convergence of this series expansion has not been possible. We have tried to analyze the effects of incorporating the effects of including mass variation inside a star on the computation of its equipotential surfaces while computing the equilibrium structures as well as periods of oscillations of rotating stars and stars in binary system. The problem of the validity of series expansions for certain parameters has also been considered.