Collaborative Research: A Fresh Look at M Dwarf Stars

超过70%的恒星是“M矮星”，它们比太阳小得多，温度低得多，亮度也低。更好地理解它们的物理性质涉及星系化学演化，星系动力学，恒星大气，分子天体物理学，星星形成，行星形成和系外行星特征。 该小组将通过联合恒星内部和大气的最佳物理模型并通过高质量的观测来测试它们来促进我们的理解。这些项目有一个重要的培训组成部分，因为大部分工作将由加州大学圣克鲁斯，亚利桑那州州立大学和波士顿大学的研究生完成。本科生也将参与这项研究，该团队将创建一个新的课程和培训材料，包括一个网络研讨会，让学生了解未来的职业。该团队将对M矮星的大气、内部和演化进行全面的建模研究。以前对M矮星物理学的研究使用了为更大质量的恒星设计的方法和代码，工作人员将质量降低到M矮星。这个小组将使用为褐矮星开发的建模工具，褐矮星的质量比M星低，然后质量上升来建模这些物体。M矮星和棕矮星有许多共同的特性，比如分子主导的大气和部分退化的内部。 该团队将使用M星的光谱“检索”模型，这是一种完全由贝叶斯数据驱动的方法，以产生最适合的温度结构和丰度，而不受预先计算的大气网格的约束。 他们将把重点放在基准上，在类似太阳的初级恒星轨道上进行充分研究的M星。 根据这项工作的结果，他们将计算一个大的辐射对流模型大气网格，以产生温度、重力和金属丰度的趋势，这将对整个天文学界有用。这样的模型也将作为新的自洽M矮星演化模型与梅萨，其中将包括一个新的氢状态方程的上边界条件。这将使他们能够与以前的理论和观测工作进行详细的比较M矮大气，它们在H-R图上的位置，以及观察到的质量半径关系。这个奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Over 70% of all stars are “M dwarfs”, which are much smaller, cooler, and less luminous than the Sun. A better understanding of their physical properties touches on galactic chemical evolution, the dynamics of the galaxy, stellar atmospheres, molecular astrophysics, star formation, planet formation, and exoplanet characterization. This group will advance our understanding by uniting the best physical models of stellar interiors and atmospheres and testing them with high-quality observations. These projects have an important training component, as much of the work will be done by graduate students at UC Santa Cruz, Arizona State University, and Boston University. Undergraduate students will also be involved in the research, and the team will create a new curriculum and training materials, including a webinar for students to learn about future careers. The team will carry out a thorough modeling study of M dwarf atmospheres, interiors, and evolution. Previous work on M dwarf physics has used methods and codes devised for more massive stars, with workers moving down in mass to M dwarfs. This group will use modeling tools developed for brown dwarfs, just lower in mass than the M stars, and then move up in mass to model these objects. M dwarfs and brown dwarfs share many properties, like molecule-dominated atmospheres and partially degenerate interiors. This team will use spectral "retrieval" models for M stars, a fully Bayesian data-driven method, to yield best-fit temperature structures and abundances that are not bound to pre-computed atmosphere grids. They will focus on benchmark, well-studied M stars in orbit around Sun-like primaries. Based on the outcomes of this work, they will then compute a large grid of radiative-convective model atmospheres to yield trends in temperature, gravity, and metallicity, which will be of use to the entire astronomical community. Such models will also serve as the upper boundary conditions for new self-consistent M dwarf evolution models with MESA, which will include a new hydrogen equation of state. This will allow them to pursue detailed comparisons with previous theoretical and observational work on M dwarf atmospheres, their locations on the H-R diagram, and observed mass-radius relations.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.