Collaborative Research: Understanding exoplanets orbiting fully convective stars with the Habitable-zone Planet Finder

该团队将使用10米霍比-埃伯利望远镜上的多普勒光谱仪——宜居带行星发现者（HPF），对距离地球8秒差距内的M级红矮星以及距离地球更远的小于M4级的恒星进行调查。该团队将尝试通过宿主恒星发出的光的特征径向速度（RV）颜色波动来识别这些系统中的系外行星。人们对这些较小恒星周围的系外行星数量知之甚少。该团队试图回答这样的问题：在完全对流的恒星周围，系外行星系统是什么样子的？在低质量的主星周围，超级地球的比例是否有所增加？该团队希望为即将到来的超大望远镜的后续成像建立一个目标群。该团队将开展各种外展活动，包括在麦克唐纳天文台举办教师研讨会，在加州大学欧文分校为来自代表性不足群体的学生提供指导，以及参与HPF博客。该团队还将培训研究生作为工作的一部分。HPF调查将提供的数据主要用于回答两个问题。首先，研究小组将确定围绕完全对流恒星运行的系外行星的发生率，作为行星大小和轨道周期的函数。先前的系外行星调查表明，M矮星通常拥有小型行星，并且有微弱的证据表明，在M星中后期，较大的超级地球和海王星大小的行星的频率增加。然而，这些调查仍然以早期m亚型（更大质量的恒星）为主；这项调查将为M型的完全对流端行星人口提供经验证据。其次，团队将解决恒星抖动的问题。来自恒星磁活动的天体物理噪声或“抖动”正在迅速成为RV测量中的限制性噪声源，M矮星也不例外。然而，完全对流的恒星对磁发电机和非常红的光谱能量分布知之甚少。这意味着它们表面的磁现象和用于诊断它们的可观测数据可能与类日恒星不同。凭借其稳定的仪器轮廓和近红外波长覆盖范围，HPF将提供对抖动现象的关键见解，并支持其贡献的复杂模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The team will use the Habitable-zone Planet Finder (HPF), a Doppler spectrometer on the 10-m Hobby-Eberly Telescope, to conduct a survey of Class M red dwarf stars within 8 parsecs of Earth, as well as stars smaller than Class M4 further from Earth. The team will attempt to identify exoplanets in these systems from characteristic radial velocity (RV) color fluctuations in light emitted by the host stars. The exoplanet population around these smaller stars is poorly understood. The team seeks to answer the question of what exoplanetary systems look like around fully convective stars, and whether there is an increase in the fraction of super-Earths around lower-mass host stars. The team hopes to build a population of targets for follow-up imaging by upcoming Extremely Large Telescopes. The team will conduct a variety of outreach activities, including a teacher workshop at the MacDonald Observatory, mentorships at UC Irvine for students from under-represented groups, and participation on the HPF blog. The team will also train graduate students as part of the work.The HPF survey will provide data principally to answer two questions. First, the team will determine the occurrence rates for exoplanets orbiting fully-convective stars as a function of planet size and orbital period. Previous exoplanet surveys have shown that M dwarfs typically host small planets, and there is tenuous evidence that the frequency of larger super-Earth and Neptune-sized planets increases for mid-to-late M stars. However, these surveys are still dominated by early-M subtypes (more massive stars); this survey will offer empirical evidence for the planet population of the fully-convective end of the M type. Second, the team will tackle the problem of stellar jitter. Astrophysical noise, or "jitter," originating from stellar magnetic activity is rapidly becoming the limiting noise source in RV measurements, and M dwarfs are no exception. However, fully convective stars have poorly understood magnetic dynamos and very red spectral energy distributions. This means both the magnetic phenomena on their surfaces and the observables used to diagnose them may differ from those of Sunlike stars. With its stable instrument profile and NIR wavelength coverage, HPF will provide critical insights into jitter phenomena and support sophisticated models of its contribution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.