Types of Contact Binary Systems and Ways to Find Them

Abstract

Generally, the designation of contact system among close binary systems means that the components are so close that they are physically touching each other or are joined together. They can be classified into four distinct groups based on the characteristics of their common atmospheres: late-type low mass systems (W UMa systems) with common convective atmospheres, early-type massive systems with common radiative atmospheres, mix- or intermediate-type systems consisting of a cooler component with a convective stellar atmosphere and a hotter companion with a radiative stellar atmosphere, and supergiant contact systems with very deep common convective atmospheres. In addition, there is one very peculiar group called double contact systems. In these systems, each of their components is being in contact with its respective critical equal potential surface but the components are not in physical contact with each other!