RUI: Understanding Close White Dwarf Binaries Using Planetary Nebula Central Stars

所有恒星中有三分之一到二分之一是在双星系统中发现的，许多在它们进化的后期阶段将成为紧密的白矮星（WD）双星，这是一个由两个紧密间隔的白矮星或一个WD-主序对组成的短暂阶段。这些天体在许多天体物理背景中发挥着重要作用，包括双星演化中的“共同包层”（CE）阶段，非球形行星状星云（PNe）的形成，灾难性变量（如新星），以及Ia型超新星（SNe）的交替路径，后者作为关键的宇宙距离指标。深入了解这些系统的形成和演化取决于扩大已知例子的列表，特别是那些构成行星状星云（CSPNe）中心恒星的例子，这是瓦尔帕莱索大学一个研究项目的主要目标。这项工作还将支持本科生的直接参与，并利用东南天文研究协会（SARA）天文台进一步发展天文实验室。将进行光度和光谱观测活动，其具体目标是使现有的已知近双星CSPNe加倍（从90颗增加到160颗）。对新发现的CSPNe双星（以及已知的例子）的更详细的后续观测将用于双星建模，以提供详细的系统参数，如每颗恒星的质量、半径和温度。新增加的一组已知参数将用于更好地理解双白矮星（DWD）双星和带主序星（MS）伴星的白矮星双星的形成。该研究小组正在研究DWD系统的蒙特卡罗分析和二元演化计算。这项工作将随着观察到的样本量的增加而扩大和更新。研究人员还将使用结果来测试现有的蒙特卡罗，种群进化和CE计算，并且结果将供其他研究人员用作未来建模的约束。结果还将提供DWD合并率、SN Ia率和SN Ia延迟时间分布（DTD）的独立度量。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。

Between one third to one half of all stars are found in binary systems, and many in their late evolutionary stages will become close white dwarf (WD) binary stars, a short-lived stage consisting of either two closely spaced WDs or a WD-main sequence pair. These objects play an important role in many astrophysical contexts, including the “common envelope” (CE) phase in binary star evolution, non-spherical planetary nebulae (PNe) formation, cataclysmic variables (e.g., novae), as well as alternate pathways to type Ia supernovae (SNe), the latter serving as a key cosmological distance indicator. Insights into the formation and evolution of these systems depends on expanding the list of known examples, particularly those making up the central stars in planetary nebulae (CSPNe), which is the primary goal of a research program at Valparaiso University. This work will also support direct participation by undergraduate research students and further develop astronomy labs utilizing the Southeastern Association for Research in Astronomy (SARA) Observatory.Photometric and spectroscopic observing campaigns will be undertaken with the specific goal of doubling (from 90 to 160) the existing set of known close binary CSPNe. More detailed follow-up observations of the newly discovered binary CSPNe (as well as known examples) will be used with binary modeling to provide detailed system parameters such as each star’s mass, radius, and temperature. The newly increased set of known parameters will then be used to better understand the formation of double white dwarf (DWD) binaries and white dwarf binaries with a main sequence (MS) companion. The research team is working on Monte Carlo analysis and binary evolution calculations for DWD systems. That work will be expanded and updated as the observed sample size increases. The researchers will also use the results to test existing Monte Carlo, population evolution, and CE computations and the results will be available for other researchers to use as future constraints to their modeling. The results will also provide independent measures of DWD merger rates, SN Ia rates, and the SN Ia delay time distribution (DTD).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.