标题： 一颗年轻低质量恒星周围的等离子环 显示英文标题

标题： A Plasma Torus Around a Young Low-Mass Star

摘要： 年龄小于1亿年的红矮星中有一小部分显示出结构化的周期性光学光变曲线，这暗示可能存在与恒星共同旋转的不透明物质凌星现象。然而，这种物质的组成、起源甚至是否存在都尚不确定。主要的替代假设是这些复杂的周期性变化变量（CPVs）可以通过恒星表面亮区或暗区的复杂分布来解释。 在这里，我们展示了对一颗快速旋转（$P$=3.9 小时）的 CPV 星，TIC 141146667 的时序光谱和测光数据。光谱显示，在恒星赤道速度的两倍到四倍处出现了正弦时间变化的 H$\alpha$发射线，这直接证明了在 CPV 的共同旋转区域存在冷却（$\lesssim$10$^4$ K）等离子体团块。这些数据支持年轻且快速旋转的 M 型矮星能够维持类似其他快速旋转磁星的冷却等离子体扭曲环。 尚未解决的问题包括这些等离子体环中的尘埃团是否可以解释 CPV 光变曲线，以及这些环是源自恒星本身还是由外部来源供给。粗略估计表明，大约有$\gtrsim$10% 的 M 型矮星在其早期生命阶段具有类似的结构。 显示英文摘要

摘要： A small fraction of red dwarfs younger than 100 million years show structured, periodic optical light curves suggestive of transiting opaque material that corotates with the star. However, the composition, origin, and even the existence of this material are uncertain. The main alternative hypothesis is that these complex periodic variables (CPVs) are explained by complex distributions of bright or dark regions on the stellar surfaces. Here, we present time-series spectroscopy and photometry of a rapidly-rotating ($P$=3.9 hr) CPV, TIC 141146667. The spectra show sinusoidal time-varying H$\alpha$ emission at twice to four times the star's equatorial velocity, providing direct evidence for cool ($\lesssim$10$^4$ K) plasma clumps trapped in corotation around a CPV. These data support the idea that young, rapidly-rotating M dwarfs can sustain warped tori of cool plasma, similar to other rapidly-rotating magnetic stars. Outstanding questions include whether dust clumps in these plasma tori explain CPV light curves, and whether the tori originate from the star or are fed by external sources. Rough estimates suggest $\gtrsim$10% of M dwarfs host similar structures during their early lives.