On the Evolution of Close Binary Systems.
Frank Wood · The Astronomical Journal · 1960
Three problems in the study of close binaries are large ranges in mass ratios, many departures from the mass4uminosity relation, and the fact that when one component fills the Jacobian limiting surface, this is usually the less massive component. Efforts to explain these by large scale mass transfer have not shown how this can be done without disturbing the equilibrium. A protostar with two condensation centers will become a binary. Recent work on the evolution of single stars suggests that the contraction centers probably have a higher initial condensation of dust to gas than the medium from which they are condensing, and later will attract the gas which comprises most of the star. In the case of a close binary, these centers will compete for the gas (chiefly hydrogen) in the medium from which the stars form. If one center is more massive than the other, its contraction stages will take place more rapidly. At the time this component reaches the main sequence, the less massive component will not be able to retain the material lying outside the Jacobian limiting surface, and this must be acquired by the other component or be lost to the system. Qualitatively this concept offers a possible answer to the problems cited. The mass ratios may become large because much of the original mass was either lost or acquired by the more massive star. The secondary component will be hydrogen-poor, and hence will have a higher central temperature than normal for its mass and the composition of the original mixture; thus its departure from mass luminosity would always be in the same direction. If the heavier component also loses mass it will be overluminous for the same reason; if it does not, it will be normal; if it acquires much of the hydrogen which otherwise would have gone to the secondary, it will be underluminous. These cases all exist. Finally, the less massive components will be found at the limiting boundary surfaces, not because of normal evolution, but because the matter beyond this limit was lost to the other component or to the entire system.