Advanced evolutionary stages of lower mass stars

低质量恒星的高级演化阶段

• 批准号: 1150-2007
• 负责人: VandenBerg, Don
• 金额: $ 4.66万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=473443
• 关键词: Advanced; evolutionary; stages; lower; mass

The main thrust of my research over much of my career has been to produce stellar models that satisfy observational constraints as tightly as possible - focusing primarily on main-sequence and giant-branch stars. Indeed, additional work on these phases will be carried out in the near term. For instance, the impact on the predicted temperature scale of using model atmospheres as boundary conditions for the stellar interior models will be examined in collaboration with B. Gustafsson's Uppsala group. In addition, isochrones applicable to metal-poor stars that take diffusive processes into account will be computed in collaboration with colleagues at the U. of Montreal. However, the main goal of my research over the next several years is to extend the published grids to include the horizontal-branch (HB) and asymptotic-giant-branch (AGB) phases, so that University of Victoria stellar models may be used to study complex stellar populations. Initially these models will be applied to globular star clusters to try to obtain an improved understanding of the so-called "second-parameter problem" (the unknown cause of the wide diversity in HB morphology encompassed by clusters having very similar metallicities), and to refine current estimates of the cluster helium abundances. Moreover, the pulsational characteristics of the models will be computed using a code provided by G. Fontaine, in order to make use of the constraints provided by the cluster RR Lyrae variables. To generate AGB models much more efficiently than existing programs (by about a factor of 5), a hybrid code will be set up having a Lagrangian mode to follow the evolution, nucleosynthesis, and mixing during He shell flashes in considerable detail (using techniques developed by F. Herwig), as well as a non-Lagrangian mode (i.e., the method of solving the stellar structure equations developed by P. Eggleton) to follow the evolution of thin nuclear-burning shells between consective shell flashes. With such a code, it will be possible to explore parameter space much more fully than has been possible to date, and thereby to improve our understanding of this evolutionary phase, which plays an especially important role in the chemical evolution of galaxies.

在我职业生涯的大部分时间里，我研究的主要目标是产生尽可能严格满足观测约束的恒星模型--主要集中在主序星和巨支星上。 事实上，近期内将开展关于这些阶段的更多工作。 例如，将与B合作研究使用模型大气作为恒星内部模型的边界条件对预测温度标度的影响。古斯塔夫松的乌普萨拉集团 此外，将与美国国家天文台的同事合作计算适用于贫金属恒星的等时线，并将扩散过程考虑在内。蒙特利尔。 然而，我的研究在未来几年的主要目标是扩大已公布的网格，包括水平分支（HB）和渐近巨星分支（AGB）阶段，使维多利亚大学的恒星模型可以用来研究复杂的恒星种群。 最初，这些模型将被应用到球状星星集群，试图获得一个更好的理解所谓的“第二参数问题”（未知原因的广泛多样性HB形态所包含的集群具有非常相似的金属丰度），并完善目前的估计集群氦丰度。 此外，模型的脉动特性将使用G.方丹，以便利用集群RR Lyrics变量提供的约束。 为了比现有程序更有效地生成AGB模型（大约5倍），将建立一个混合代码，该代码具有拉格朗日模式，以相当详细地跟踪He壳闪光期间的演化、核合成和混合（使用F. Herwig），以及非拉格朗日模式（即，由P. Eggleton开发的恒星结构方程的求解方法），以跟踪连续壳闪光之间薄核燃烧壳的演化。 有了这样一个代码，就有可能比迄今为止更全面地探索参数空间，从而提高我们对这一演化阶段的理解，这在星系的化学演化中起着特别重要的作用。