Dynamical evolution of active detached binaries on the log Jo–log M diagram and contact binary formation
Dynamical evolution of active detached binaries on the log Jo–log M diagram and contact binary formation
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DOI：
10.1111/j.1365-2966.2006.11073.x
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发表时间：
2006-09
影响因子：
4.8
通讯作者：
Z. Eker;O. Demircan;S. Bilir;Y. Karatas
中科院分区：
文献类型：
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作者：
Z. Eker;O. Demircan;S. Bilir;Y. Karatas
研究了色球活跃双星 (CAB) 和大熊座 W (W UMa) 系统的轨道角动量 (OAM, J o )、系统质量 (M) 和轨道周期 (P) 分布。 log J o -logP、logM-logP 和 log J o -log M 图由 119 颗 CAB 和 102 颗 W UMa 星组成。人们发现 log J o -log M 图对于展示双星轨道的动态演化最有意义。在 log J o -log M 图上发现了一条稍微弯曲的边界线（接触边界），将分离系统和接触系统分开。由于双星的轨道大小 (a) 和周期 (P) 由它们当前的 J o 、M 和质量比 q 决定，OAM 损失率 (d log J o /dt) 和质量损失率 (d log M/dt) 是确定动力学演化方向和速度的主要参数。如果一个分离系统自身的动态演化使其能够通过 log J o -log M 图上的接触边界，那么它就成为接触系统。除非每个组件的质量损失率已知，否则质量损失分离系统的 q 演化是未知的。假设 q 在第一近似中恒定，并使用 CAB 恒星运动年龄的 Jo 和 M 的平均递减率，预测当前 CAB 恒星中的 11%、23% 和 39% 将转变为 W UMa 系统，如果它们的核演化允许它们分别存活 2、4 和 6 Gyr。
Orbital angular momentum (OAM, J o ), 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 log J o -logP, logM-logP and log J o -log M were formed from 119 CAB and 102 W UMa stars. The log J o -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 J o -log M diagram. Since the orbital size (a) and period (P) of binaries are determined by their current J o , M and mass ratio, q, the rates of OAM loss (d log J o /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 eontact system if its own dynamical evolution enables it to pass the contact border on the log J o -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.