从百万年到回转年的自转-活动关系
The Age-Rotation-Activity Relation: From Myrs to Gyrs
摘要：
在过去的40年里，观测调查已经建立了恒星的年龄，自转周期和磁场活动之间的紧密关系。这种年龄-自转-活动关系记录了恒星的磁发电机和角动量演化之间的相互作用，并为孤立场恒星提供了一个有价值的年龄估计。虽然年龄旋转活动的关系已被广泛研究，在集群小于5亿年，经验测量的旋转周期是稀缺的老年人。利用帕洛玛瞬变工厂（PTF），我们已经开始了一项恒星自转巡天，以绘制出年龄-自转-活动关系的后期演化：哥伦比亚/康奈尔/加州理工PTF（CCCP）对疏散星团的巡天。第一个CCCP目标是附近的约6亿年Hyades-类似Praesepe，PTF已经产生了超过3个月的光变曲线，包含约650个集群成员的>150个测量值。通过分析这些光变曲线，我们测量了40个K & M星团成员的自转周期，填补了以前报道的太阳型毕宿星团（Radick et al. 1987，Prosser et al. 1995）和少数低质量Praesepe成员（Scholz et al. 2007）的周期之间的空白。我们的测量结果表明，Praesepe的周期颜色关系在过渡的特征光谱类型的~M1 -从一个定义良好的奇异关系在较高的质量，在较低的质量更分散的分布的快速和慢速旋转。这一转变的位置与基于对年轻星团的观测的预期大致一致，并且假设恒星自旋下降是影响约6亿年角动量演化的主要机制。除了介绍我们的Praesepe光度监测的结果，我们总结了CCCP调查的现状和未来。
英文摘要：
Over the past 40 years, observational surveys have established the existence of a tight relationship between a star's age, rotation period, and magnetic activity. This age-rotation-activity relation documents the interplay between a star's magnetic dynamo and angular momentum evolution, and provides a valuable age estimator for isolated field stars. While the age-rotation-activity relation has been studied extensively in clusters younger than 500 Myr, empirically measured rotation periods are scarce for older ages. Using the Palomar Transient Factory (PTF), we have begun a survey of stellar rotation to map out the late-stage evolution of the age-rotation-activity relation: the Columbia/Cornell/Caltech PTF (CCCP) survey of open clusters. The first CCCP target is the nearby ~600 Myr Hyades-analog Praesepe, where PTF has produced light curves spanning more than 3 months and containing >150 measurements for ~650 cluster members. Analyzing these light curves, we have measured rotation periods for 40 K & M cluster members, filling the gap between the periods previously reported for solar-type Hyads (Radick et al. 1987, Prosser et al. 1995) and for a handful of low-mass Praesepe members (Scholz et al. 2007). Our measurements indicate that Praesepe's period-color relation undergoes at transition at a characteristic spectral type of ~M1 --- from a well-defined singular relation at higher mass, to a more scattered distribution of both fast and slow-rotators at lower masses. The location of this transition is broadly consistent with expectations based on observations of younger clusters and the assumption that stellar-spin down is the dominant mechanism influencing angular momentum evolution at ~600 Myr. In addition to presenting the results of our photometric monitoring of Praesepe, we summarize the status and future of the CCCP survey.
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