CAREER: Mixing and Oscillations in Novae

职业：Novae 中的混合和振荡

• 批准号: 2238851
• 负责人: William Wolf
• 金额: $ 52.68万
• 依托单位: University of Wisconsin-Eau Claire
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2028-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2238851&HistoricalAwards=false
• 关键词: CAREER; Mixing; Oscillations; Novae

White dwarfs are the dense remnants of stars like our sun after their nuclear fuel runs out. Often, they are found in binary systems (two stars orbiting each other). In such systems, the two stars can exchange matter as they age and change size. When white dwarfs gain material from a companion, they undergo explosions on their surfaces, known as novae, losing some or all of the gained matter to space. If such a white dwarf can grow in mass appreciably over many novae, it can be totally destroyed in a massive explosion known as a type Ia supernova. Type Ia supernovae produce roughly half of the iron in the universe and are used as distance measures in cosmology, but we do not fully understand what causes them. In this project, the investigator and a team of undergraduate researchers will use the Modules for Experiments in Stellar Astrophysics (MESA) software tool to study mass-gaining white dwarfs. They will clarify how nova explosions affect the long-term evolution of white dwarf masses. Additionally, they will investigate how X-ray emission from a nova may be used to measure the mass of the underlying white dwarf. Freely available educational activities utilizing MESA for use in undergraduate astrophysics courses will be developed.This program will probe the effects of diffusion, rotation, and convective boundary mixing on the mass retention efficiency of novae. The group will investigate each mechanism individually before combining two and all three at a time. Since these mixing mechanisms can cause core material to be ejected in the nova event, they may lead to a net mass loss over a single nova cycle. This study will constrain what circumstances, if any, allow a white dwarf to grow to the Chandrasekhar mass from hydrogen accretion alone, shedding light on the Type Ia supernova progenitor problem. To aid in measuring white dwarf masses, the group and collaborators will analyse the MESA models with the open-source GYRE stellar oscillation software to determine if the dominant core oscillation modes in nova models match the observed oscillations in the post-outburst X-ray emission of novae. If such a link can be established, it would provide a robust measure of white dwarf mass and perhaps composition. The investigator will develop online materials to train other researchers on using MESA.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.

白色矮星是像我们的太阳这样的恒星在核燃料耗尽后的致密残余物。通常，它们存在于双星系统中（两颗恒星相互环绕）。在这样的系统中，两颗恒星可以随着年龄和大小的变化而交换物质。当白色矮星从同伴那里获得物质时，它们的表面会发生爆炸，称为新星，将部分或全部获得的物质释放到太空中。如果这样的一颗白色矮星的质量可以在许多新星之上明显地增长，那么它就可以在一次被称为Ia型超新星的大爆炸中被完全摧毁。Ia型超新星产生了宇宙中大约一半的铁，并被用作宇宙学中的距离测量，但我们并不完全了解它们的成因。在这个项目中，研究人员和一组本科生研究人员将使用恒星天体物理学实验模块（梅萨）软件工具来研究质量增加的白色矮星。他们将阐明新星爆炸如何影响白色矮星质量的长期演化。此外，他们还将研究如何利用新星发射的X射线来测量底层白色矮星的质量。将开发利用梅萨供本科天体物理学课程使用的免费教育活动，该方案将探索扩散、旋转和对流边界混合对新星质量保持效率的影响。该小组将分别研究每种机制，然后将两种机制和所有三种机制同时结合起来。由于这些混合机制可能导致核心物质在新星事件中被喷射出来，它们可能导致在单个新星周期中的净质量损失。这项研究将限制什么样的情况下，如果有的话，允许一个白色矮星从氢吸积单独增长到阿布拉塞卡质量，揭示了Ia型超新星的祖先问题。为了帮助测量白色矮星的质量，该小组和合作者将用开源的GYRE恒星振荡软件分析梅萨模型，以确定新星模型中的主导核心振荡模式是否与观察到的爆发后新星X射线发射的振荡相匹配。如果能够建立这样的联系，它将提供一个可靠的测量白色矮星的质量和组成的方法。 该奖项反映了NSF的法定使命，并被认为值得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来支持。