On the Reflection of Light in a Close Binary System

Abstract

Among the eclipsing variable stars which have been studied in recent years there are a number which in addition to the eclipse variation show a marked increase of light as the fainter component moves from inferior to superior conjunction. The physical interpretation of this so-called “radiation effect” is obviously the increased brightness of the faint companion on the side toward the primary, for in the systems where this effect is conspicuous the least distance between the surfaces of the two components does not much exceed the diameter of the main body. This increase of intensity on one side of the companion may be attributed in part to reflection, but because of the energy of radiation received at a small distance from the central star, any body would be heated up to incandescence. In the case of Algol it may be shown that the surface of the companion toward the main star must receive per unit area more radiation than is emitted from the surface of the sun, and since a condition of equilibrium has been reached, the companion must be incandescent on one side, though probably it is hot enough on its own account to be self-luminous independent of the primary.

The following investigation was carried on more than ten years ago, while I was spending a sabbatical year at Munich, and I was much indebted to Geheimrat Seeliger for various suggestions. I am now glad to join with other students of Seeliger in honor of his anniversary, which should be an occasion for congratulations from astronomers of every land.