THE MASS-DEPENDENCE OF ANGULAR MOMENTUM EVOLUTION IN SUN-LIKE STARS
THE MASS-DEPENDENCE OF ANGULAR MOMENTUM EVOLUTION IN SUN-LIKE STARS
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DOI：
10.1088/2041-8205/799/2/l23
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发表时间：
2014-12
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通讯作者：
S. Matt;A. Brun;I. Baraffe;J. Bouvier;Gilles Chabrier University of Exeter;UK.;C. Saclay;France;'Ecole Normale Sup'erieure de Lyon;U. G. Alpes;Cnrs;Ipag;Grenoble
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作者：
S. Matt;A. Brun;I. Baraffe;J. Bouvier;Gilles Chabrier University of Exeter;UK.;C. Saclay;France;'Ecole Normale Sup'erieure de Lyon;U. G. Alpes;Cnrs;Ipag;Grenoble
为了更好地理解观测到的类太阳和低质量恒星的旋转速率和磁活动分布，我们推导了一个物理驱动的尺度，用于恒星风转矩对罗斯比数的依赖。扭矩也包含了经验推导出的恒星质量（和半径）的比例，这为恒星磁场和风性质对质量的依赖提供了新的见解。我们证明，这个新的公式解释了为什么最低质量的恒星被观察到保持快速旋转的时间比太阳质量的恒星长得多，同时为什么年龄较大的恒星群表现出一系列缓慢旋转的恒星，其中低质量的恒星旋转得比太阳质量的恒星慢。该模型还再现了开普勒场的周期-质量图中一些以前无法解释的特征，特别是：分布的“上包膜”的特殊形状，表明开普勒场中有测量到的旋转周期的恒星中有95%的恒星年龄小于4 Gyr；以及“下包层”的形状，对应于恒星在磁性饱和和不饱和状态之间转换的位置。
To better understand the observed distributions of the rotation rate and magnetic activity of Sun-like and low-mass stars, we derive a physically motivated scaling for the dependence of the stellar wind torque on the Rossby number. The torque also contains an empirically derived scaling with stellar mass (and radius), which provides new insight into the mass-dependence of stellar magnetic and wind properties. We demonstrate that this new formulation explains why the lowest mass stars are observed to maintain rapid rotation for much longer than solar-mass stars, and simultaneously why older populations exhibit a sequence of slowly rotating stars, in which the low-mass stars rotate more slowly than solar-mass stars. The model also reproduces some previously unexplained features in the period–mass diagram for the Kepler field, notably: the particular shape of the “upper envelope” of the distribution, suggesting that ∼95% of Kepler field stars with measured rotation periods are younger than ∼4 Gyr; and the shape of the “lower envelope,” corresponding to the location where stars transition between magnetically saturated and unsaturated regimes.