量化短时标恒星活动对M型矮星凌星探测的影响
Quantifying the Effect of Short-timescale Stellar Activity Upon Transit Detection in M Dwarfs
AI总结：
本文利用TESS观测的Hα活跃与不活跃M型矮星，在剔除自转和大耀发后开展凌星注入回收，量化未分辨短时标活动对不同半径和周期行星探测信噪比及灵敏度的影响。
摘要：
M型矮星占银河系恒星总数的70%至80%，并拥有银河系中的大多数岩石行星。它们还与类太阳恒星存在重要差异：在数十亿年甚至更长时间内都处于“活跃”状态，表现为快速自转、频繁耀发，并辐射大量紫外光和X射线。恒星活动对测光和光谱学的影响使其系外行星更难被探测，而M型矮星表现出这种行为的时间比典型类太阳恒星长数千倍。尽管耀发和恒星自转等活动信号较容易在测光数据中建模或移除，但未分辨的恒星活动对凌星灵敏度的贡献更难量化。本文研究NASA的TESS任务观测的一组M型矮星周围行星凌星可探测性的差异；这些恒星具有共同的恒星半径、有效温度和TESS星等特征。我们根据Hα发射线的存在，将样本划分为“活跃”或“不活跃”两类。在移除更容易识别的活动特征（恒星自转和大型耀发）之后，我们对每颗恒星进行凌星注入与回收分析。我们为样本中的每颗恒星提取作为行星半径和轨道周期函数的探测灵敏度。随后，为便于比较，我们分别生成“活跃”恒星和“不活跃”恒星的平均灵敏度图。在将活跃恒星与具有相同温度和视亮度的不活跃恒星进行比较时，我们量化了凌星探测中信噪比降低的程度。我们希望这些灵敏度图能在未来的M型矮星行星发生率研究中为系外行星界提供帮助。
英文摘要：
M dwarf stars comprise 70-80% of the galaxy's stars and host most of its rocky planets. They also importantly differ from Sunlike stars in that they are "active" for billions of years or more: rotating quickly, flaring often, and emitting large amounts of UV and X-ray light. The effects of stellar activity upon both photometry and spectroscopy make their exoplanets more difficult to detect, and M dwarfs exhibit this behavior for thousands of times longer than a typical Sunlike star. While activity signals such as flaring and stellar rotation can be more readily modeled or removed from photometry, the contribution of unresolved stellar activity to transit sensitivity is harder to quantify. In this paper, we investigate the difference in the detectability of planetary transits around a sample of M dwarfs observed by NASA's TESS Mission, characterized by a common stellar radius, effective temperature, and TESS magnitude. Our sample is classified as either "active" or "inactive" based upon the presence of H$α$ in emission. After removing the more readily identifiable signatures of activity: stellar rotation and large flares, we perform an injection-and-recovery analysis of transits for each star. We extract detection sensitivity as a function of planetary radius and orbital period for each star in the sample. Then, we produce averaged sensitivity maps for the "active" stars and the "inactive" stars, for the sake of comparison. We quantify the extent to which signal-to-noise is degraded for transit detection, when comparing an active star to an inactive star of the same temperature and apparent brightness. We aim for these sensitivity maps to be useful to the exoplanet community in future M dwarf occurrence rate studies.
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