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Characterizing potentially habitable planets around low mass stars is a key focus of current and upcoming missions such as JWST and TESS. This focus stresses the need for a comprehensive understanding of the radiation environments in which such planets reside. Low-mass stars are typically much more active than solar type stars and the proximity of their habitable zones can be one tenth the distance. The far-ultraviolet (FUV) radiation emitted by these stars has the potential to alter an orbiting planet.s atmospheric photochemistry comma while the extreme-ultraviolet (EUV) radiation can cause the loss of planetary atmospheres and surface volatiles. Ly-a emission at 1216 A is the dominant radiation source for low mass stars at FUV wavelengths and is critical for informing stellar atmosphere models used to predict the EUV spectrum comma but directly measuring a low-mass star.s Ly-a emission is almost always impossible because of the contaminating effects of interstellar hydrogen. Using Gaia DR2 comma we have identified a unique sample of six low mass stars for which a complete and accurate measurement of their Ly-a line profile is possible due to their very large radial velocities. Stars with very large radial velocities (>100 km-s) will have their Ly-a emission Doppler shifted away from contaminating sources allowing for the rare opportunity to measure intrinsic Ly-a emission. These proposed observations of this rare sample of stars will triple the number of stars with Ly-a emission measured in this way and will improve the accuracy of computed spectra for all low-mass stars across wavelengths that drive planetary atmospheric evolution.

对低质量恒星周围潜在宜居行星的特性表征工作，是当前及未来诸如詹姆斯·韦布空间望远镜（JWST）、凌日系外行星巡天卫星（TESS）等航天任务的核心研究方向。这一研究重点凸显了全面认知此类行星所处辐射环境的迫切需求。低质量恒星通常比太阳型恒星更为活跃，且其宜居带与恒星的距离仅为日地距离的十分之一。此类恒星辐射的远紫外（FUV）辐射，可改变环绕行星的大气光化学过程；而极紫外（EUV）辐射则会导致行星大气与表面挥发物的散失。波长1216埃的莱曼α（Ly-a）辐射是低质量恒星远紫外波段的主要辐射源，对构建用于预测极紫外光谱的恒星大气模型至关重要；但受星际氢的污染影响，几乎无法直接测量低质量恒星的莱曼α辐射。借助盖亚数据发布2（Gaia DR2），我们筛选出一组特殊的6颗低质量恒星样本：得益于它们极大的径向速度，我们可完整且精准地测量其莱曼α谱线轮廓。径向速度极高（>100 km/s）的恒星，其莱曼α辐射会因多普勒效应发生频移，从而脱离污染辐射源的波段范围，这为我们提供了难得的直接测量恒星本征莱曼α辐射的机会。本次针对该稀有样本的观测计划，将使通过此类方式测得莱曼α辐射的恒星数量增至三倍，同时还将提升所有低质量恒星在驱动行星大气演化的各波段上的计算光谱精度。