Wave Transport of Angular Momentum: A New Spin on Massive-Star Evolution

角动量的波传递：大质量恒星演化的新旋转

• 批准号: 0908688
• 负责人: Richard Townsend
• 金额: $ 42.8万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0908688&HistoricalAwards=false
• 关键词: Wave; Transport; Angular; Momentum; New

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Townsend will undertake an exploration of the incidence, characteristics and evolutionary impact of wave transport by oscillation modes in massive stars. The foundation for this exploration will lie in a new Self-Consistent Spectrum (SCS) method for incorporating the transport into stellar evolution calculations. At the heart of the SCS method is a pair of numerical codes: a non-radial, non-adiabatic pulsation code, which will be developed as part of the project's initial activities, and an evolution code, which will be derived from an already-existing code. As massive stars evolve across the main sequence, they pass through one or more instability strips where oscillation modes are excited by an opacity-regulated heat engine. During these phases, the unstable modes can alter a star's rotation profile by transporting angular momentum from one part of the interior to another. This wave transport has potentially far-reaching consequences for the star's subsequent evolution and ultimate fate, but in studies so far it has largely been overlooked. The SCS method will first be used to explore various wave-transport phenomena discovered during an earlier pilot study: the self-limitation of mode amplitudes via the angular velocity gradients that they establish; the acceleration of surface layers by retrograde gravity modes, and its relation to the Be-star phenomenon; and the mixing of molecular weight gradient zones due to the interplay between wave transport and shear instability. Subsequently, the method will be applied in a comprehensive survey of massive-star evolution with the full inclusion of wave transport. This survey, based around the calculation of a large grid of evolutionary tracks, will be used to address many important questions relating to the wave transport, ranging from its observational diagnostics through to its impact on final evolutionary outcomes. The project results will be disseminated in the form of journal papers, presentations, calculation data, parametric models, and a browser-based stellar evolution code for research and education. The pulsation code will be released under an open-source license, to encourage other groups' involvement in exploring wave transport, and also as an analysis tool for asteroseismology of massive stars. A graduate student and postdoctoral researcher composing part of the project team will benefit from training in topics with steadily growing scientific visibility and relevance. This training will in turn stimulate the development of new curriculum materials for undergraduate/graduate courses. The project results will be broadly disseminated through papers, presentations, data and models. Moreover, with the release of source code and the development of on-line tools, the project will enhance infrastructure for research and education.

该奖项是根据2009年《美国回收与再投资法》（公共法第111-5）.DR资助的。汤森德（Townsend）将对巨大恒星中振荡模式的波传输的发病率，特征和进化影响进行探索。这种探索的基础将是一种新的自洽频谱（SCS）方法，该方法将运输纳入恒星进化计算中。 SCS方法的核心是一对数值代码：一种非radial，非绝热脉动代码，该代码将作为项目初始活动的一部分开发，以及将从已经存在的代码衍生而来的Evolution Code。 随着巨大的恒星在整个主序列中演变，它们通过一个或多个不稳定性条，在该条带上不透明度调节的热发动机激发振荡模式。在这些阶段中，不稳定的模式可以通过将角动量从内部的一个部分传输到另一部分来改变恒星的旋转曲线。这次波运输对恒星随后的进化和最终命运带来了潜在的深远影响，但是在迄今为止的研究中，它在很大程度上被忽略了。 SCS方法将首先用于探索在较早的试点研究中发现的各种波传输现象：通过它们确定的角速度梯度对模式振幅的自限；通过逆行重力模式加速表面层的加速度，及其与BE-Star现象的关系；以及由于波传输与剪切不稳定性之间的相互作用而导致的分子量梯度区域的混合。随后，该方法将在全面包含波传输的情况下对大型明星进化进行全面调查。这项调查基于大量进化轨道网格的计算，将用于解决与波传输有关的许多重要问题，从其观察诊断到对最终进化结果的影响。项目结果将以期刊论文，演示，计算数据，参数模型以及基于浏览器的研究和教育的恒星演化代码的形式传播。脉动代码将在开源许可下发布，以鼓励其他群体参与探索波浪运输，也是作为大型恒星星星学的分析工具。一名研究生和博士后研究人员组成项目团队的一部分将受益于科学知名度和相关性稳步增长的主题培训。这项培训反过来将刺激本科/研究生课程的新课程材料的开发。项目结果将通过论文，演示，数据和模型大致传播。此外，随着源代码的发布和在线工具的开发，该项目将增强研究和教育的基础设施。