Critical Tests of Stellar Evolution Theory

恒星演化理论的关键测试

• 批准号: 0708229
• 负责人: Guillermo Torres
• 金额: $ 42.76万
• 依托单位: Smithsonian Institution Astrophysical Observatory
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0708229&HistoricalAwards=false
• 关键词: Critical; Tests; Stellar; Evolution; Theory

Despite significant advances in recent decades in our understanding of the evolution and internal structure of stars, many aspects of theory remain untested or have been shown to disagree with observations. Evolutionary models are widely used by astronomers to infer various properties of stars such as the masses, ages, or overall chemical abundances, but our confidence in these models is limited to some extent by those disagreements and by a lack of observational constraints. Carefully selected binary systems are ideal objects to test and validate theory through a comparison with accurate measurements of fundamental stellar quantities such as the stellar mass, the radius, the effective temperature, or the luminosity. The aim of this project is to obtain these measurements for a number of astrophysically important systems and to perform "critical" tests of stellar evolution theory, namely, tests that can distinguish between competing models and are able to rule out at least some of them. Only in this way can progress be made towards understanding in detail where theory fails and how stars work. Specific areas that will be tested are the theory of convection (mixing length theory, overshooting), internal structure (apsidal motion, including relativistic contributions), rotation, mass loss, and tidal evolution (rotational synchronization and orbit circularization due to tidal forces). This project will go beyond merely showing the overall agreement with one or another set of models. The goal is to provide so many observational constraints for a given binary system that only the most realistic sets of models (if any) may satisfy all the observations within the errors, simultaneously for both stellar components and at a single evolutionary age (since they are presumably coeval). This project will focus on low-mass stars (which have highlighted many problems with theory), evolved stars (giants and subgiants) and very young (pre-main sequence) stars for which virtually no constraints are available, as well as stars with chemical compositions very different from the Sun (metal-poor). High quality spectroscopic, photometric, and astrometric observations will be obtained and analyzed to make determinations of the absolute stellar properties with relative errors no larger than 1-2% in the case of the masses and radii, which is the current state-of-the-art.The dissemination of the results to the scientific community mainly in the form of peer-reviewed publications is an integral part of this project. It is expected that this work will significantly advance our understanding of several poorly known areas of stellar astrophysics as indicated above. Improving theory will not only allow much more reliable determinations of parameters such as the ages of stars (old and young), which have profound cosmological implications, but it will also provide a more solid framework for the study of the origin and evolution of substellar objects such as brown dwarfs and extrasolar planets, which in recent years have become a subject of great interest for the public and scientists alike. This project will also provide excellent opportunities for training by integrating front-line research into the experience of learning. Two Ph.D. students will work with Dr. Torres towards completing their dissertations on binaries, and two postdoctoral associates as well as several undergraduates are expected to participate actively in all stages of this project.

尽管近几十年来我们对恒星演化和内部结构的理解取得了重大进展，但理论的许多方面仍未经过检验或已被证明与观测结果不一致。天文学家广泛使用演化模型来推断恒星的各种属性，例如质量、年龄或总体化学丰度，但我们对这些模型的信心在某种程度上受到这些分歧和缺乏观测约束的限制。精心挑选的双星系统是通过与恒星质量、半径、有效温度或光度等基本恒星量的精确测量进行比较来测试和验证理论的理想对象。该项目的目的是获得许多天体物理重要系统的测量结果，并对恒星演化理论进行“关键”测试，即可以区分竞争模型并能够排除至少其中一些模型的测试。只有这样，才能在详细理解理论失败的地方以及恒星如何运作方面取得进展。将测试的具体领域包括对流理论（混合长度理论、超调）、内部结构（近轴运动，包括相对论贡献）、旋转、质量损失和潮汐演化（由于潮汐力导致的旋转同步和轨道圆化）。该项目将不仅仅是显示与一组或另一组模型的总体一致性。目标是为给定的双星系统提供如此多的观测约束，只有最现实的模型集（如果有的话）才能满足误差范围内的所有观测，同时对于两个恒星成分和单个进化年龄（因为它们可能是同时代的）。该项目将重点关注低质量恒星（这凸显了理论中的许多问题）、演化恒星（巨星和亚巨星）和非常年轻的（前主序星）恒星（几乎没有可用的约束），以及化学成分与太阳非常不同的恒星（贫金属）。将获得和分析高质量的光谱、光度和天体测量观测结果，以确定恒星的绝对属性，在质量和半径的情况下，相对误差不大于1-2%，这是当前最先进的。主要以同行评审出版物的形式向科学界传播结果是该项目的一个组成部分。预计这项工作将显着增进我们对如上所述的恒星天体物理学几个鲜为人知的领域的理解。改进的理论不仅可以更可靠地确定恒星年龄（老的和年轻的）等参数，这些参数具有深远的宇宙学意义，而且还将为研究棕矮星和太阳系外行星等亚恒星天体的起源和演化提供更坚实的框架，这些天体近年来已成为公众和科学家们非常感兴趣的课题。该项目还将通过将前沿研究融入学习体验中，提供绝佳的培训机会。两名博士学生们将与托雷斯博士一起完成有关二进制文件的论文，预计两名博士后和几名本科生将积极参与该项目的所有阶段。