Photometric Effects for Highly Distorted White Dwarf Secondaries in Close Binary Systems

Abstract

As a by-product of an analysis of the light curves of the early-type close binary systems (Ruciński 1969a), similar computations for the highly distorted white dwarf hypothetical secondaries of certain peculiar systems were made. The computations were carried out numerically by integrating the monochromatic fluxes emerging from the atmosphere over the visible surface of the star. The effects of eclipses were not taken into account; the reflection effect was also excluded at this step of analysis. A slightly different model atmosphere was used at each point of the star’s surface depending on the local effective temperature (with the assumption of von Zeipel proportionality T_e ∼ g ^1/4). The shape, variations of the effective gravitaty g, and the cosine of the angle between the local normal to the surface and the direction to the observer, μ, were described using the first order perturbation theory for close binary systems (Chandrasekhar 1933). In that theory the Legendre polynomial P₂ gives the ellipticity of the star; the next P₃ and P₄ polynomials describe respectively the non-symmetric and symmetric deviations from ellipticity.