THE STRUCTURE AND PULSATION OF STARS

Abstract

This thesis is an attempt to study some aspects of the pulsation theory of variable stars. The thesis is divided into two parts. A detailed introduction to the present work and a chapter-wise summary of the contents of the thesis is given in chapter I. The equation for small, adiabatic radial oscillations is derived in the second chapter and the solution is obtained for two models. The third chapter deals with two models for commensurable case and the fourth with the effect of central condensation, and the effect of surface gravity on some of pulsation characteristics. The fifth and sixth chapters deal with anharmonic pulsations of some polytropic models. t ,, In part two, we consider the pulsations of an early ( main sequence star of ten solar masses. In chapter VII, a it detailed investigation is made regarding its anharmonic ^ pulsations. An attempt has been made here (and also in Part I) to study the effects of higher modes, the inclusion of different number of terms, and the variation of the amplitude of pulsation on the shape and skewness of the radial velocity curve. Inclusion of the non-adiabatic effects of the outer layers and the contribution of the second helium ionization towards the pulsational stability of the model and the observed phase lag of the model has been explored in chapter VIII. -11- In chapter IX besides obtaining some other results, the results obtained in the previous chapters have been fully discussed. They are also compared with the observations and the theoretical results obtained by other workers and conclusions drawn.