CAREER: Fundamental properties of young and pre-main-sequence stars

恒星构成了许多现代天文学的基础，并直接影响到宇宙距离尺度、星系结构和演化、化学元素的合成、行星形成和生命起源等不同的子领域。因此，精确了解恒星的基本参数，如质量、半径、年龄和光度是必不可少的。然而，对于年轻的低质量恒星，由于在这一群体中缺乏能够准确确定这些量的已知日食和天体测量双星，因此在这方面的知识存在很大差距。这项拟议的研究将利用最近由Gaia、K2和Tess调查确定的双星系统，得出年轻、低质量恒星的准确光度、半径、年龄和质量。该项目还将支持一名研究生和几名本科生的研究活动，以及首席研究员为天文学课程开发互动活动的努力，以及基于这项研究为北卡罗来纳大学教堂山校园的莫尔黑德天文馆制作的互动/多媒体展览。研究人员将通过分析低质量日食和天体测量双星样本的光曲线，得出年龄为500-5亿年的K&M恒星的恒星参数，准确度高于5%。这是一种经过验证的方法，通常应用于年龄更大、质量更大的恒星。使用这些系统作为“基准”，他们将推导出经验的质量-光度-年龄关系，调查磁活动对所得参数的影响，并根据给定年龄的直接观测数据确定恒星半径、光度和表面温度的经验关系。他们将使用光谱确定的锂丰度，并通过对多个种群的显式建模，进一步探索星团中的年龄分布。这项工作的一个主要动机是为年轻的行星宿主提供更好的参数，然而，直接可观测性和基本性质之间的推导关系将适用于广泛的科学应用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Stars form the foundation upon which much of modern astronomy rests and directly impact sub- fields as diverse as the cosmic distance scale, galaxy structure and evolution, the synthesis of chemical elements, planet formation, and the origin of life. Precise knowledge of basic stellar parameters such as mass, radius, age, and luminosity are thus essential. However, substantial gaps in this knowledge exist for young, low-mass stars due to the paucity of known eclipsing and astrometric binary stars among this population that enable accurate determinations of these quantities. The proposed research will derive accurate luminosities, radii, ages, and masses for young, low-mass stars using binary systems recently identified by Gaia, K2, and TESS surveys. This project will also support research activities by a graduate and several undergraduate students, as well as efforts by the principal investigator to develop interactive activities for astronomy courses and an interactive/multimedia-based exhibit based on this research for the Morehead Planetarium on the UNC Chapel Hill campus.The researchers will derive stellar parameters to better than 5% accuracy for 5-500 million year old K & M stars through the analysis of light curves in a sample of low-mass eclipsing and astrometric binary systems. This is a proven method that is routinely applied to older, more massive stars. Using these systems as ``benchmarks’’ they will derive empirical mass-luminosity-age relations, investigate the impact of magnetic activity on the derived parameters, and determine empirical relations for stellar radii, luminosity, and surface temperature from direct observables given an age. They will further explore age distributions in star clusters using spectroscopically determined lithium abundances and through explicit modeling of multiple populations. A major motivation of this work is to provide improved parameters for young planetary hosts, however the derived relations between direct observables and fundamental properties will be applicable to a wide variety of scientific applications.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.