The Variable Period of W Delphini

Volume 2 number 1 (1973)

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Douglas S. Hall

Abstract

The tendency for the period changes in eclipsing binaries to appear sinusoidal led astronomers in the first half of this centruy to suggest apsidal motion or orbital motion around a third body as explanations. Clear-cut examples of both of these phenomena have been found; but as more and more time of minimum are observed and the base line in time gets longer, it has become clear that in the large majority of cases the period variations are not really sinusoidal or even periodic.