2006/09/14 by Z. Eker, O. Demircan, S. Bilir +2 · 2 citations
Physics and Astronomy · #Angular momentum #Astro and Planetary Science #Astrophysics #Astrophysics and Star Formation Studies #Binary number #Binary star #Classical mechanics #Contact binary #Diagram #Mass ratio #Orbital period #Physics #Stars #Statistics #Stellar evolution #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2006.11073.x
published as Mon.Not.Roy.Astron.Soc.373:1483-1494,2006 · 28 pages, including 6 figures and 2 tables, accepted for publication in MNRAS
arxiv created 2006/09/14 · openalex publication_date 2006/11/17 · arxiv updated 2009/12/01 · openalex created_date 2020/11/23 · openalex updated_date 2026/08/05
Orbital angular momentum (OAM, Jo), systemic mass (M) and orbital period (P) distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W UMa) systems were investigated. The diagrams of and log Jo–log M were formed from 119 CAB and 102 W UMa stars. The log Jo–log M diagram is found to be most meaningful in demonstrating dynamical evolution of binary star orbits. A slightly curved borderline (contact border) separating the detached and the contact systems was discovered on the log Jo–log M diagram. Since the orbital size (a) and period (P) of binaries are determined by their current Jo, M and mass ratio, q, the rates of OAM loss (d log Jo/dt) and mass loss (d log M/dt) are primary parameters to determine the direction and the speed of the dynamical evolution. A detached system becomes a contact system if its own dynamical evolution enables it to pass the contact border on the log Jo–log M diagram. The evolution of q for a mass-losing detached system is unknown unless the mass-loss rate for each component is known. Assuming q is constant in the first approximation and using the mean decreasing rates of Jo and M from the kinematical ages of CAB stars, it has been predicted that 11, 23 and 39 per cent of current CAB stars would transform to W UMa systems if their nuclear evolution permits them to live 2, 4 and 6 Gyr, respectively.