Irradiation effects in close binaries in an electron scattering medium

Abstract

In a close binary system, the effects of irradiation are studied from an extended surface of the secondary component on the atmosphere of the primary. Primary and the secondary components are assumed to have equal radii and the thickness of the atmosphere is assumed to be twice that of the stellar radius of the primary component. Self radiation of the primary component (Ss) is calculated through a numerical solution of line transfer equation in the comoving frame with Compton broadening due to electron scattering. The solution is developed through discrete space theory to deal with different velocities in a spherically expanding medium. The irradiation from the secondary (SI ) is calculated using one dimensional rod model. It is assumed to be one, five and ten times the self radiation. The total source function (S = Ss + SI) is the sum of the source functions due to self radiation and that due to irradiation. The line fluxes are computed along the line of sight by using the above source functions. Line profiles are also computed for different line center optical depths along the line of sight of the observer at infinity. We noticed that the source functions against the optical depth show order of magnitude difference in the medium with and without reflection and also with the proximity of the secondary component. It is also noticed that the expansion of the medium produces P Cygni type profiles and the irradiation enhances the emission in the lines.