RUI: Using a Large Sample of White Dwarf Stars to Study Stellar Evolution

对绝大多数恒星来说，白矮星是恒星演化的终点。因此，它们是研究恒星生命周期最后阶段的有用的法医探测器。白矮星是一种致密的恒星，其体积与太阳的质量相当（大约比地球小一百万倍）。白矮星不再像太阳那样经历核聚变，而是在数十亿年的时间里继续散发余热。德克萨斯农工大学商学院的一个研究小组将执行一项计划，利用盖亚太空任务的数据，结合地面望远镜的观测，将年轻疏散星团（或由几千颗年龄大致相同的恒星组成的星团）中已知的WDs样本增加一倍。这些科学家将利用这些大样本的WDs来解决一系列天体物理学领域的几个悬而未决的问题，包括：恒星演化后期恒星总质量损失的可变性，超新星或恒星爆炸的较低质量，近距离多星系统的演化，以及行星系统的命运。该项目将扩大现有的成功努力，通过提供资金来培训和指导本科生学习助理，以修改后的、以学习者为中心的天文学入门课程，提高本科生在STEM入门课程中的学习和保留。该项目还将为第一代大学生和来自贫困农村地区的代表性不足的学生提供参与天文学研究的机会。疏散星团中的白矮星是研究恒星生命周期最后阶段的多功能和强大的法医探测器。特别是，白矮星研究使我们能够约束恒星在后主序演化过程中的总质量损失，核心坍缩超新星祖先的质量下限，双简并系统的形成速率，红巨星核心的旋转速率及其与恒星包膜的耦合，以及白矮星大气和结构演化。疏散星团中的白矮星在很大程度上是特别有用的工具，因为许多关键的恒星参数是已知的，包括总年龄（白矮星冷却时间加上祖星寿命）和金属丰度。该项目建立在早期研究人员对疏散星团中的白矮星的研究基础上；来自盖亚任务的视差和固有运动数据以及疏散星团的多历元深度成像几乎消除了星团成员的不确定性，大大减少了目前在已发表的文献中做出的推断数量。通过使用国家、州和地方大学的设施，研究人员希望将已知疏散星团白矮星的数量增加近一倍，并能够实施白矮星形成和演化的整体研究。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。

White dwarf (WD) stars are the endpoint of stellar evolution for the vast majority of stars. As such, they are useful forensic probes for studying the end stages of the stellar life cycle. A white dwarf is a compact star that contains the mass of the Sun within a volume comparable to that of the Earth (about a million times smaller). White dwarfs no longer undergo nuclear fusion like the Sun, but continue to glow from residual heat for billions of years. A research group at Texas A&M University-Commerce will carry out a program to use data from the Gaia space mission combined with observations from ground-based telescopes to double the sample of known WDs in young open clusters, or groupings of a few thousand stars of about the same age. These scientists will use this large sample of WDs to address several open questions in a range of astrophysical areas including: variability in total mass lost by stars during late stages of stellar evolution, the lower mass of the progenitors of supernovae, or stellar explosions, the evolution of close multiple star systems, and the fate of planetary systems. This project will expand an existing successful effort to improve undergraduate student learning and retention in introductory STEM classes by providing funding to train and mentor undergraduate learning assistants for revised, learner-centered introductory astronomy courses. The project will also offer first-generation college students and underrepresented students from depressed rural areas opportunities to participate in astronomy research.White dwarf stars in open star clusters are versatile and powerful forensic probes for studying the end stages of the stellar life cycle. In particular, white dwarf studies allow us to constrain the total mass lost by stars during their post-main sequence evolution, the lower mass limit for core-collapse supernova progenitors, the formation rate of double degenerate systems, rotation rates of red giant cores and their coupling to the star's envelope, and white dwarf atmospheric and structural evolution. White dwarfs in open star clusters are especially useful tools in large part because the many crucial stellar parameters are known, including total age (white dwarf cooling time plus progenitor lifetime) and metallicity. The project builds on earlier studies of white dwarf stars in open clusters made by the investigators; parallax and proper motion data from the Gaia mission and multi-epoch deep imaging of open clusters virtually eliminates uncertainties in cluster membership, vastly reducing the number of inferences currently made in the published literature. Through the use of national, state and local university facilities, the researchers expect to nearly double the number known open cluster white dwarfs and to be able to implement ensemble studies of white dwarf formation and evolution.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.