WoU-MMA: The White Dwarf Mass Distribution and the Gravitational Wave Foreground from Double White Dwarfs

白矮星（WD）是极其紧凑的物体，是与太阳质量相似的恒星的残骸，这些恒星耗尽了核燃料，但它们的余热可以发光数十亿年。俄克拉荷马大学和史密森天体物理天文台之间的一项研究合作将研究WDs的数量统计，重点是极低质量（ELM）双WDs，它们彼此绕轨道运行，周期短至几分钟。这些研究对天体物理学非常重要，因为双或双WDs预计将成为未来天基重力波天文台（如计划中的LISA任务）探测到的重力波（GW）的主要来源。预计它们最终也会合并，导致Ia型超新星的恒星爆炸或超新星（SN）， Ia型超新星是一种重要的超新星类型，用于测量宇宙的膨胀率。研究人员将使用来自盖亚太空任务的数据来识别候选的ELM WDs，然后使用地面望远镜来确认候选的ELM WDs并确定其特征。他们还将研究距离地球约300光年内所有质量的WDs的全部数量。该项目将为研究生和本科生提供研究机会，包括代表性不足的群体成员。与他们的研究相结合，首席研究员和他的学生将通过月球探测器外展小组，为来自俄克拉荷马州夏延-阿拉帕霍和其他部落的童子军团体、初高中学生和K-12学生提供互动演示、讲座、问答小组和观星活动。利用盖亚任务的视差，可以很容易地识别出ELM白矮星，因为与平均质量的白矮星相比，它们的亮度过高。这些WDs是周期短至12分钟的超紧凑双星系统的标志。找到这样的双星对于近期的种群合成研究，对于表征来自双WDs的mHz频率范围内的预期GW前景，以及对于显着增加LISA验证源的数量非常重要。测量良好的WD双星将成为最好的电磁和GW实验室之一，用于理解致密物体的形成，双星中的动态相互作用和潮汐，以及Ia型SNe等能量现象。盖亚100pc WD样本基本上是完整的，但在颜色/绝对星等序列中包含一个意想不到的分叉，这主要是由大气成分解释的。然而，氢大气WDs的分布需要大量的WDs（大约0.8-1太阳质量），这可能与合并的WDs双星有关。该项目将获得无偏WD质量分布，并限制大规模WD的频率。这个项目推进了NSF宇宙大构想窗口的目标。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 extremely compact objects that are the remnants of stars of similar mass to the Sun, which have exhausted their nuclear fuel, but shine for billions of years from their residual heat. A research collaboration between the University of Oklahoma and the Smithsonian Astrophysical Observatory will study the population statistics of WDs, with an emphasis on extremely low-mass (ELM) double WDs, orbiting each other with periods as short as a few minutes. These studies are very important for astrophysics, since double or binary WDs are expected to be major sources of gravitational waves (GW) detected by future space-based GW observatories such as the planned LISA mission. They are also expected to eventually merge, leading to a stellar explosion or supernova (SN), of Type Ia, an important type of supernova that is used to measure the expansion rate of the universe. The investigators will use data from the Gaia space mission to identify candidate ELM WDs, and then use ground based telescopes to confirm the candidates and determine their characteristics. They will also study the entire population of WDs of all masses within about 300 light years of Earth. This project will provide research opportunities for graduate and undergraduate students, including members of under-represented groups. In conjunction with their research, the principal investigator and his students will provide interactive demonstrations, lectures, question and answer panels, and stargazing events to scout groups, middle and high school students, and K-12 students from Cheyenne-Arapaho and other tribes across Oklahoma, through the Lunar Sooners outreach group. Using parallaxes from the Gaia mission, ELM white dwarfs can be readily identified, since they are over-luminous compared to average mass WDs. These WDs are the signposts of ultra-compact binary systems with periods as short as 12 minutes. Finding such binaries is important for near-term population synthesis studies, for characterizing the expected GW foreground in the mHz frequency range from double WDs, and for significantly increasing the number of LISA verification sources. Well-measured WD binaries will be among the best Electromagnetic plus GW laboratories for understanding the formation of compact objects, dynamical interactions and tides in binaries, and energetic phenomena like Type Ia SNe. The Gaia 100 pc WD sample is essentially complete but contains an unexpected bifurcation in the color/absolute magnitude sequence that is mostly explained by the atmospheric composition. However, the distribution of hydrogen atmosphere WDs requires a population of massive (around 0.8-1 solar mass) WDs, which may be linked to merging WD binaries. This project will obtain an unbiased WD mass distribution and constrain the frequency of massive WDs. This project advances the goals of the NSF Windows on the Universe Big Idea.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.