发表机构
School of Astronomy and Space Science, University of Chinese Academy of Sciences; National Astronomical Observatories, Chinese Academy of Sciences; Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University; New Cornerstone Science Laboratory, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院大学天文与空间科学学院; 中国科学院国家天文台; 北京师范大学天文与天体物理前沿研究院; 中国科学院国家天文台新基石科学实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究基于钱德拉与XMM-牛顿观测，发现F/G型矮星X射线演化呈两阶段、K/M型呈三阶段，且低质量恒星日冕辐射主导性更强，不同类型恒星周围行星的XUV环境存在差异。
AI 中文摘要
恒星的X射线辐射是日冕活动的直接诊断指标，与日冕加热过程存在根本关联，同时还会强烈影响其轨道系外行星的大气层及长期宜居性。因此，研究这种高能辐射的演化，对理解恒星磁发电机的演化以及行星大气层与宜居性至关重要。本研究基于钱德拉（Chandra）和XMM-牛顿望远镜的观测数据，调查了F型至M型矮星样本的X射线活动与极紫外（XUV）辐射演化。研究发现，F型和G型恒星大致遵循传统演化图像：早期为饱和（或微弱衰减）阶段，随后进入适度衰减阶段；而K型和M型恒星则呈现清晰的三阶段演化：饱和阶段、快速衰减的中间阶段，以及最终的适度衰减阶段。通过结合X射线、紫外和Ca II H&K波段数据，研究表明，质量越低的恒星，其日冕辐射的主导性越强。基于拟合关系计算得到的累积XUV辐射，F型和G型恒星周围的行星所处的XUV环境相对温和；而K型和M型恒星周围的行星，在到达主序后不久便可能超出经验宇宙海岸线，不过该结论取决于所采用的海岸线取值。
英文摘要
Stellar X-ray emission serves as a direct diagnostic of coronal activity, which is fundamentally linked to coronal heating processes. It also strongly influences the atmospheres and long-term habitability of orbiting exoplanets. Investigating how this high-energy emission evolves is therefore essential for understanding the evolution of stellar magnetic dynamos and planetary atmospheres and habitability. In this work, we investigate the evolution of X-ray activity and XUV irradiation for a sample of F-M dwarf stars based on Chandra and XMM-Newton observations. We find that F- and G-type stars broadly follow the traditional evolutionary picture of an early saturated (or weakly declining) phase followed by a modest decline, whereas K- and M-type stars exhibit a clear three-phase evolution of a saturated phase, an intermediate phase of rapid decay, and a final modest decline phase. By combining X-ray, ultraviolet, and Ca II H&K bands, we show that coronal emission becomes increasingly dominant toward lower-mass stars. Based on the cumulative XUV emission calculated from our fitted relation, planets around F- and G-type stars experience relatively moderate XUV environments, while those around K- and M-type stars may exceed the empirical cosmic shoreline shortly after reaching the main sequence, though this conclusion depends on the adopted shoreline value.
Comments22 pages, 16 figures, 3 tables. Accepted for publication in ApJS
