Abstract:
For theoretical modeling of binary systems, one has to consider
realistic models which takes into account the radiative transfer, hydrodynamics,
and the effect of irradiation from the secondary component on the atmosphere
of primary component. Since the problem is complex, we studied in the thesis
idealized models which will help us in understanding the important physical
processes in close binaries. As a first step to understand the reflection effect we
have developed a method of obtaining radiation field from the spherical surface
irradiated by an external (i) point source (ii) extended source of radiation in
close binary systems. The method has been extended in the case of atmospheres
distorted due to self rotation of the component and tidal effects due to the presence
of its companion. In all the cases we used two-level atom approximation
with complete redistribution in calculating the spectral lines formed in the atmosphere
of the primary star. The effects of irradiation from the secondary
component on the atmosphere of the primary is calculated depending upon the
geometrical shape of the illuminated surface, proximity of the secondary component
to the primary and ratio of the luminosities of the primary and the
secondary. We calculated the line profiles with various parameters like density
and velocity variations.
We notice that the expansion of the medium produces P Cygni type profiles
and the irradiation enhances the emission in the lines although the equivalent
widths reduce considerably. In the case of rotationally distorted star without
tidal forces we find the radiation to be diluted. Close binary systems with tidal
distortion produce emission profiles filling the self absorption from the primary
component.
