Modeling White-Dwarf Merger Events: The R Coronae Borealis Stars

白矮星合并事件建模：R Coronae Borealis 恒星

• 批准号: 1814967
• 负责人: Geoffrey Clayton
• 金额: $ 50.62万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1814967&HistoricalAwards=false
• 关键词: Modeling; White; Dwarf; Merger; Events

Stellar mergers are mysterious phenomena that pack a broad range of physical processes into a small volume and a fleeting time duration. In a merger, two stars become one as their structures and evolution are violently perturbed. A stellar merger is a natural experiment that can help astronomers answer important questions about stellar evolution. The R Coronae Borealis (RCB) stars are rare, hydrogen-deficient, carbon-rich, supergiant stars surrounded by circumstellar dust. It has been suggested that there is a possible connection between the RCB stars and certain stellar explosions called Type Ia supernovae (SNe), where both classes arise when two white dwarf stars (WDs) merge. A research group at Louisiana State University (LSU) plans to study RCB stars in detail using computer models to simulate the evolution of an RCB star to answer questions about their formation, lifetime, and evolution into a different type of star. By investigating this type of WD merger, the LSU group will also help to better understand the origin of Type Ia SNe, which are important for understanding the expansion of the universe. The researchers will continue to participate in outreach efforts including public observing nights and talks, involving amateur astronomers in research projects and developing innovative distance learning and online astronomy courses that will reach large numbers of the public. They are also training the next generation of astronomy researchers and working to increase diversity in astronomy.The LSU group plans to simulate the evolution of an RCB star using a combination of their new self-gravitating hydrodynamics code and MESA, a 1-D stellar evolution module. Their new code, Octo-tiger/HPX, is a 3-D, finite-volume adaptive mesh refinement (AMR) hydrodynamics code with Newtonian gravity. The group will develop a radiation transport module and incorporate a limited nuclear reaction network. Octo-tiger/HPX is parallelized for execution on multi-core high performance computers, which will allow them to probe new areas of parameter space such as much higher spatial resolution, much larger grids, and multiple dynamical time scales. The results of this work will not only broaden the understanding of stellar merger events that lead to RCB stars, but will also shed light on many other related objects for which mergers and common envelope evolution may play a crucial role, including contact binaries, blue stragglers, hot subdwarfs, red novae, massive star mergers, X-ray binaries, cataclysmic variables, short gamma-ray bursts, and Type Ia supernovae. Beyond the astrophysics domain, the research has promise to pave the way for other fluid simulations requiring a high degree of linear and angular momentum conservation, nuclear simulation, multi-physics simulation, and AMR techniques.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.

恒星合并是一种神秘的现象，它将一系列广泛的物理过程打包成一个小体积和短暂的持续时间。在合并中，两颗恒星的结构和演化受到剧烈的干扰，因此成为一颗恒星。恒星合并是一项自然的实验，可以帮助天文学家回答关于恒星进化的重要问题。北冕(RCB)恒星是一种罕见的、缺氢、富碳的超大恒星，周围环绕着恒星尘埃。有人提出，在RCB恒星和某些被称为Ia型超新星(SNE)的恒星爆炸之间可能存在联系，当两颗白矮星(WD)合并时，这两类恒星都会出现。路易斯安那州立大学(LSU)的一个研究小组计划使用计算机模型来详细研究RCB恒星，以模拟RCB恒星的演化，以回答有关它们的形成、寿命和演化为不同类型恒星的问题。通过研究这种类型的WD合并，路易斯安那州立大学的研究小组还将有助于更好地理解Ia型SNE的起源，这对于理解宇宙的膨胀非常重要。研究人员将继续参与外联工作，包括公众观察之夜和讲座，让业余天文学家参与研究项目，并开发将惠及大量公众的创新远程学习和在线天文课程。他们还在培训下一代天文学研究人员，并努力增加天文学的多样性。路易斯安那州立大学的团队计划使用他们新的自引力流体动力学程序和一维恒星演化模块MESA的组合来模拟RCB恒星的演化。他们的新程序Octo-Tiger/HPX是一个带有牛顿重力的三维有限体积自适应网格细化(AMR)流体动力学程序。该小组将开发一个辐射传输模块，并纳入一个有限的核反应网络。Octo-Tiger/HPX被并行化，以便在多核高性能计算机上执行，这将允许它们探索参数空间的新领域，如更高的空间分辨率、更大的网格和多个动态时间尺度。这项工作的结果不仅将拓宽对导致RCB恒星的恒星合并事件的理解，而且还将阐明许多其他相关天体，其中合并和共同的包络演化可能在其中发挥关键作用，包括接触双星、蓝散星、热矮星、红新星、大质量恒星合并、X射线双星、激变变星、短伽马射线爆发和Ia型超新星。在天体物理学领域之外，这项研究有望为其他需要高度线性和角动量守恒的流体模拟、核模拟、多物理模拟和AMR技术铺平道路。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。

项目成果

Octo-Tiger’s New Hydro Module and Performance Using HPX+CUDA on ORNL’s Summit

• DOI: 10.1109/cluster48925.2021.00059
• 发表时间: 2021-07
• 期刊: 2021 IEEE International Conference on Cluster Computing (CLUSTER)
• 作者: Patrick Diehl;Gregor Daiß;Dominic C. Marcello;K. Huck;Sagiv Shiber;Hartmut Kaiser;J. Frank;G. Clayton;D. Pflüger

Modelling R Coronae Borealis stars: effects of He-burning shell temperature and metallicity

北欧冕 R 星建模：He 燃烧壳层温度和金属丰度的影响

• DOI: 10.1093/mnras/staa2526
• 发表时间: 2020
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Crawford, Courtney L;Clayton, Geoffrey C;Munson, Bradley;Chatzopoulos, Emmanouil;Frank, Juhan
• 通讯作者: Frank, Juhan

Harnessing billions of tasks for a scalable portable hydrodynamic simulation of the merger of two stars

利用数十亿个任务对两颗恒星合并进行可扩展的便携式流体动力学模拟

• DOI: 10.1177/1094342018819744
• 发表时间: 2018
• 期刊: The International Journal of High Performance Computing Applications
• 作者: Heller, Thomas;Lelbach, Bryce Adelstein;Huck, Kevin A.;Biddiscombe, John;Grubel, Patricia;Koniges, Alice E.;Kretz, Matthias;Marcello, Dominic;Pfander, David;Serio, Adrian
• 通讯作者: Serio, Adrian