Structure and Oscillations of Rotationally and Tidally Distorted White Dwarf Models of Stars

Abstract

In the present thesis we have studied the possibility of using Mohan, Saxena and Agarwal approach to obtain the effect of rotation and tidal forces on the equilibrium structures and the eigenfrequencies of the radial and nonradial modes of oscillations of theoretical models of the stars. Mathematical models of rotationally and tidally distorted stars have been developing in general and used to compute the equilibrium structures and eigenfrequencies of small adiabatic modes of oscillations of certain rotationally white dwarfs. Effects of tidal distortion, occurring due the presence of companion’s stars in binary system, on the equilibrium structure and periods of oscillations rotating stars have also been discussed. The study is expected to help in understanding the limitations and scope of Mohan, Saxena structure and pulsations of theoretical models of stars. Thesis consists of three chapters. Chapter I is introductory in nature. in this chapter we briefly discuss the astrophysical significance of the problem of determining the equilibrium structure and periods of small adiabatic oscillations of rotationally and tidally distorted stellar models of stars .A brief summary of literature available on the subject is also presented in this chapter and summary of the work presented in the succeeding chapter of the thesis also appearing in this chapter

In chapter II we use the approach of Mohan, Saxena and Agarwal (1990) and Lal et al (2000) to determine the equilibrium structure of rotationally and tidally distorted white dwarfs models of stars under the assumptions that angular velocity of rotation is not too large .Numerical result have been computed for certain rotationally and tidally distorted white dwarfs models for the parameters and analysis the result. In chapter III we analyze the effect of rotation and tidal distortion on the eigenfrequencies of small adiabatic barotropic mode of oscillations of stars. The eigenvalued boundary value problems which determine the eigenfrequencies of small adiabatic pseudo-radial modes of oscillations of rotationally and tidally distorted white dwarf models have been formulated using Mohan, Saxena and Agarwal (1990) approach and computed the eigenfrequencies of various pseudo-radial modes of oscillations rotationally and tidally distorted white dwarfs stars with central degeneracy parameters . Chapter IV is devoted to study the effect of rotation and tidal distortion on the eigenfrequencies of small adiabatic barotropic mode of oscillations of stars. The eigenvalued boundary value problems which determine the eigenfrequencies of small adiabatic nonradial modes of oscillations of rotationally and tidally distorted white dwarf stars have been formulated using Mohan, Saxena and Agarwal (1990) approach. The eigenfrequencies of various nonradial modes of oscillations rotationally and tidally distorted white dwarfs stars with parameters have been computed using the approach ealier discussed by Mohan and Saxena(1985). Conclusions based on the present study are also summarized in this chapter.