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

对于绝大多数恒星来说，白矮星是恒星演化的终点。因此，它们是研究恒星生命周期末期的有用法医探测器。白矮星是一种致密恒星，其质量与地球的体积相当(大约小一百万倍)。白矮星不再像太阳那样经历核聚变，而是在数十亿年的余热中继续发光。德克萨斯农工大学商务部的一个研究小组将实施一个项目，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)中的已知WD样本增加一倍。这些科学家将利用这一大样本的wd来解决一系列天体物理领域中的几个公开问题，包括：恒星演化后期恒星损失的总质量的变异性，超新星或恒星爆炸的前身质量较低，近距离多恒星系统的演化，以及行星系统的命运。该项目将扩大现有的成功努力，通过提供资金培训和指导修订的、以学习者为中心的天文学入门课程的本科生学习助理，改善本科生在STEM入门课程中的学习和保持能力。该项目还将为来自贫困农村地区的第一代大学生和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多功能和强大的法医探测器，用于研究恒星生命周期的末期。特别是，白矮星研究使我们能够限制恒星在主序列后演化过程中的总质量损失，核心塌缩超新星前体的质量下限，双重简并系统的形成速度，红巨核的自转速度及其与恒星包层的耦合，以及白矮星的大气和结构演化。疏散星团中的白矮星是特别有用的工具，这在很大程度上是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前驱星体寿命)和金属丰度。该项目建立在研究人员对疏散星团中的白矮星的早期研究的基础上；来自GAIA任务的视差和自行数据以及疏散星团的多历元深度成像几乎消除了星系团成员的不确定性，极大地减少了目前出版的文献中做出的推断的数量。通过使用国家、州立和地方大学的设施，研究人员预计将使已知开放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。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。

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.