Investigating the angular momentum evolution of pre-main-sequence (PMS) stars provides important insight into the interactions between Sun-like stars and their protoplanetary disks, and the timescales that govern disk dissipation and planet formation. We present projected rotational velocities (v sin i values) of 254 T Tauri stars (TTSs) in the ∼3 Myr old open cluster NGC 2264, measured using high-dispersion spectra from the WIYN 3.5 m telescope’s Hydra instrument. We combine these with literature values of temperature, rotation period, luminosity, disk classification, and binarity. We find some evidence that weak-lined TTSs may rotate faster than their classical TTS counterparts and that stars in binary systems may rotate faster than single stars. We also combine our v sin i measurements with rotation period to estimate the projected stellar radii of our sample stars, and then use a maximum likelihood modeling technique to compare our radii estimates to predicted values from stellar evolution models. We find that starspot-free models tend to underestimate the radii of the PMS stars at the age of the cluster, while models that incorporate starspots are more successful. We also observe a mass dependence in the degree of radius inflation, which may be a result of differences in the birth-line location on the HR diagram. Our study of NGC 2264 serves as a pilot study for analysis methods to be applied to four other clusters ranging in age from 1−14 Myr, which is the timescale over which protoplanetary disks dissipate and planetary systems begin to form.

中文翻译：

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NGC 2264中低质量前主序星的旋转速度和半径估计


研究前主序 （PMS） 恒星的角动量演化为了解类太阳恒星与其原行星盘之间的相互作用以及控制盘耗散和行星形成的时间尺度提供了重要的见解。我们展示了 ∼3 Myr 旧疏散星团 NGC 2264 中 254 颗 T 金牛座恒星 （TTS） 的投影旋转速度（v sin i 值），使用 WIYN 3.5 m 望远镜的 Hydra 仪器的高色散光谱测量。我们将这些与温度、旋转周期、光度、圆盘分类和二值排序的文献值相结合。我们发现一些证据表明，弱线 TTS 可能比经典的 TTS 对应物旋转得更快，而双星系统中的恒星可能比单颗恒星旋转得更快。我们还将 v sin i 测量值与自转周期相结合，以估计样本恒星的投影恒星半径，然后使用最大似然建模技术将我们的半径估计值与恒星演化模型的预测值进行比较。我们发现，无星黑子的模型往往低估了星团年龄时PMS星的半径，而包含星斑的模型则更成功。我们还观察到桡骨膨胀程度的质量依赖性，这可能是由于 HR 图上出生线位置的不同造成的。我们对 NGC 2264 的研究作为一项试点研究，将分析方法应用于其他四个星团，年龄从 1-14 Myr 不等，这是原行星盘消散和行星系统开始形成的时间尺度。