HAZMAT I：早期M星远紫外和近紫外辐射的演化
HAZMAT I: The Evolution of Far-UV and Near-UV Emission from Early M Stars
摘要：
M型矮行星宿主高能辐射的光谱能量分布、变化和演化对于理解行星的大气演化和可居住性以及解释行星的光谱至关重要。恒星的极紫外（EUV），远紫外（FUV）和近紫外（NUV）辐射可以随着时间的推移化学改变，吸收和侵蚀大气。这使得确定这样的行星的生命周期暴露于恒星紫外线辐射的关键两个行星的大气层的演变和我们的潜力来表征it. Using早期的M恒星成员附近的年轻移动集团（YMG），采样的关键年龄在行星形成和演化，我们测量的GALEX NUV和FUV通量作为年龄的函数。中位紫外线通量保持在“饱和”水平达数亿年之久，类似于X射线辐射的观测结果。到毕宿星团的年龄（6.5亿年），我们测量到紫外线通量下降了2-3倍，然后是老（几个回旋）场星的急剧下降。超过3亿年后，活动的下降大致遵循t^{-1}。尽管有这种明显的演变，但每个年龄段观察到的排放水平仍然存在1-2个数量级的广泛范围。这些紫外线数据提供了急需的限制M矮高层大气模型，这将提供积极的EUV预测和更准确的年龄依赖的紫外线光谱输入行星光化学模型。
英文摘要：
The spectral energy distribution, variability and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV) and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups (YMGs), which sample critical ages in planet formation and evolution, we measure the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a "saturated" level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650 Myr), we measure a drop in UV flux by a factor of 2-3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300 Myr follows roughly t^{-1}. Despite this clear evolution, there remains a wide range of 1-2 orders of magnitude in observed emission levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically-motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models.
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