Abstract
It has been well known for some time that some close binary stars have a semidetached or contact configuration. Many late-type systems ----- W WMa systems ----- are known to have these configurations. Their dimensions are typically of solar mass to fractions of solar masses, and solar radius to fractions of solar radii. Early-type systems with semidetached and contact configurations have been found in recent years. Their typical dimensions are from several solar masses to tens of solar masses, and from several solar radii to tens of solar radii. Generally, both late and early-type close systems are located in the vicinity of ZAMS and TAMS in an H-R diagram. They are believed to be the result of case A or B mass exchange of close binary evolution. Some of us have been wondering why we do not find semidetached or contact systems with much larger dimensions consisting of supergiant stars?
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