Photometric Effects of Reflection in Close Binary Systems

Abstract

The aim of the present investigation has been to study the mutual illumination of two luminous spheres, reflecting light in accordance with Lambert's law, by taking into account the finite angular size of the light source. After an expository section containing an outline of our problem (Section 1), exact expressions will be set up which govern the amount of light of one sphere reflected by the other for any geometrical configuration (Section 2). In Section 3 we shall specify the flux of radiation incident upon the fully illuminated as well as penumbral zones of the reflecting component; while in the subsequent Section 4 the exact results of Section 3 will be simplified to the order of accuracy to which two fluid components of a close binary system can be regarded as spheres. Section 5 will then contain a derivation of the law governing the variation of the amount of reflected light with the phase; while the concluding Section 6 will be devoted to a brief analysis of this law, as well as to an outline of its generalization to the case of distorted binary systems, or to systems exhibiting eccentric orbits.