A SIMPLE NONLINEAR MODEL FOR THE ROTATION OF MAIN-SEQUENCE COOL STARS. I. INTRODUCTION, IMPLICATIONS FOR GYROCHRONOLOGY, AND COLOR–PERIOD DIAGRAMS
A SIMPLE NONLINEAR MODEL FOR THE ROTATION OF MAIN-SEQUENCE COOL STARS. I. INTRODUCTION, IMPLICATIONS FOR GYROCHRONOLOGY, AND COLOR–PERIOD DIAGRAMS
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主序冷星旋转的简单非线性模型 I. 简介、陀螺年代学的含义和彩色周期图。
DOI：
10.1088/0004-637x/722/1/222
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
S. Barnes
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文献类型：
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作者：
S. Barnes
本文引入一个简单的非线性模型来描述主序星上冷星的自转演化。它仅用Rossby数（Ro = P/τ）、它的倒数和两个我们用太阳和疏散星团数据指定的无量纲常数来表示。该模型有两个恒星旋转的极限情况，以前称为C和I，对应于两个观察到的年轻疏散星团中快速和缓慢旋转的恒星序列。该模型描述了恒星从具有特定质量和年龄依赖性的C型到具有不同质量和年龄依赖性的I型的演化，通过旋转间隙g将它们分开。该模型解释了恒星自转的各个方面，并提供了旋转冷星星年龄的P和τ的精确表达式，从而推广了陀螺年代学。利用它，我们计算了恒星到达旋转间隙所需的时间间隔-一个单调增加的，轻度非线性函数τ。从观测到的初始周期的范围开始，我们发现旋转周期中的（质量相关的）色散最初增加，然后随着时间的推移迅速减小。周期的初始色散对太阳质量场恒星的陀螺年龄误差的贡献高达1.28亿年。最后，我们转换到色周期空间，计算适当的等时线，并表明，该模型解释了一些详细的功能，在观察到的疏散星团的色周期图，包括位置和形状的序列，以及观察到的恒星密度在这些图表。
We here introduce a simple nonlinear model to describe the rotational evolution of cool stars on the main sequence. It is formulated only in terms of the Rossby number (Ro = P/τ), its inverse, and two dimensionless constants which we specify using solar and open-cluster data. The model has two limiting cases of stellar rotation, previously called C and I, that correspond to two observed sequences of fast and slowly rotating stars in young open clusters. The model describes the evolution of stars from C-type, with particular mass and age dependencies, to I-type, with different mass and age dependencies, through the rotational gap, g, separating them. The proposed model explains various aspects of stellar rotation, and provides an exact expression for the age of a rotating cool star in terms of P and τ, thereby generalizing gyrochronology. Using it, we calculate the time interval required for stars to reach the rotational gap—a monotonically increasing, mildly nonlinear function of τ. Beginning with the range of initial periods indicated by observations, we show that the (mass-dependent) dispersion in rotation period initially increases, and then decreases rapidly with the passage of time. The initial dispersion in period contributes up to 128 Myr to the gyro-age errors of solar-mass field stars. Finally, we transform to color–period space, calculate appropriate isochrones, and show that this model explains some detailed features in the observed color–period diagrams of open clusters, including the positions and shapes of the sequences, and the observed density of stars across these diagrams.