Mon. Not. R. Astron. Soc., 373, 1483-1494 (2006/December-3)
Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation.
EKER Z., DEMIRCAN O., BILIR S. and KARATAS Y.
Abstract (from CDS):
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 logJo-logM were formed from 119 CAB and 102 W UMa stars. The logJo-logM 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 logJo-logM 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 (dlogJo/dt) and mass loss (dlogM/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 logJo-logM 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 Joand 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.
2006 The Authors. Journal compilation © 2006 RAS
binaries: spectroscopic - stars: evolution - stars: mass-loss
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<Available at CDS (J/MNRAS/373/1483): table1.dat table2.dat>
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