Equilibrium Structure of Differentially Rotating and Tidally Distorted Polytropic Models of Star

Abstract

There are still number of mysteries about the universe and a star plays an important role in newlinethe universe. Some of the experimental results are known about the structures and newlineoscillations of stars but the model based on the radius has not been attempted. The basic aim newlineof this thesis is to make some different models to calculate structures and oscillations of newlinestars. This study is related to the computations of equilibrium structures, oscillations of newlinedifferentially rotating and tidally distorted polytrophic stellar models. Illustration of the newlineeffect of mass variation of secondary star of a binary system on the equilibrium structure of newlinedifferentially rotating and/or tidally distorted models of primary polytropic star is one of the newlinemain objectives of the present work. The analysis of the equilibrium structures, equipotential newlinesurfaces and oscillations of various differentially rotating stellar models, has been done by newlineincorporating the effect of mass variation inside the star. It is assumed that the entire mass is newlineconcentrated at the centre, therefore, Roche equipotential is obtained which is further utilized newlineto describe the equipotential surface of rotationally and tidally distorted primary component newlineof a binary system of stars. The concept of Roche equipotential with conjunction of the newlineaveraging technique of Kippenhahn and Thomas (1970) has been used to obtain stellar newlinestructures. The results obtained for structure parameters, such as volume, surface area, newlineangular velocity, have also been compared with the results obtained by other authors who newlinestudied about the stellar structures and oscillations without incorporating the effect of mass newlinevariation. In this way, the approach is also used to determine the eigen-value problem newlinedescribing the radial and non-radial modes of oscillations of differentially rotating and tidally newlinedistorted stars. However, the system of Roche Coordinates is briefly extended for this effect newlineto calculate the metric coefficients and Roche harmonics. The formulation of the newlinemathematical modelling to