Asynchronous rotation in close binary systems with circular orbits.
Abstract
The origin of asynchronism observed in some binary systems in which the components rotate much more rapidly or much more slowly than the orbital rate was investigated using Pylyser's (1988) evolutionary models of stars of 1.0, 1.5, and 2.0 solar masses. Under the assumption of rigid-body rotation, the evolution of the angular rotation velocity from the main sequence up to the red-giant branch is derived; the orbital circularity of these systems is explained by strong tidal interaction, either during the early premain-sequence phase, or, for systems containing a white dwarf, during the red-giant phase of its progenitor. It is argued that, at the zero-age main sequence (ZAMS), the binary components rotate much faster than the orbital rate. During the evolution off the ZAMS, the angular rotation rate of the components decreases, mainly because of the increase of the moment of inertia, and, possibly, because of magnetic braking.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 1989
- Bibcode:
- 1989A&A...211...56H
- Keywords:
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- Binary Stars;
- Circular Orbits;
- Stellar Evolution;
- Stellar Rotation;
- Angular Velocity;
- F Stars;
- G Stars;
- Hertzsprung-Russell Diagram;
- K Stars;
- Stellar Orbits;
- Astrophysics