Spectral Analyses of Old Stellar Populations (Stars and Stellar Evolution): VPW

本研究拟对本群球状星团中的恒星进行理论光谱计算和应用，以量化金属丰度校准，并研究轻元素相对丰度和平均恒星年龄变化的发生。这项工作将基于新扩展的库鲁兹谱线列表生成的模型和光谱，这些模型和光谱再现了太阳和太阳附近的冷巨星大角星的通量分布和单个谱线强度。拟议工作的第一阶段将是计算银河系球状星团M4、M71和47 Tucanae中单个冷巨星的模型和光谱；疏散星团M67；以及银河隆起。目的是确定总体金属丰度和轻元素氧、镁、硅、钙、钠和铝相对于铁的丰度比，以显示爆炸核合成在不同环境和时代主导元素生产的程度。在此之后，理论光谱将在太阳附近完成各种金属丰度的热恒星，包括有和没有光元素增强。然后将这些适合不同年龄星团的光谱组合与观测到的仙女座球状星团的积分光谱进行比较，同时估计铁元素和轻元素的丰度以及平均恒星年龄。这项提议的研究代表了恒星大气和元素丰度方面的“最先进”工作，它可以在我们对银河系组成和演化的理解方面取得实质性进展，即恒星的结构和元素的演化历史。该项目进一步推进了VPW项目的目标，即通过研究为女性提供在科学或工程领域发展的机会，并通过研究人员在东道国校园中作为榜样的知名度提高，鼓励其他女性在这些领域追求职业。在这一努力中，对第二个目标有贡献的拟议活动包括：在一门关于恒星大气的研究生课程中，就恒星丰度的现实分析进行客座讲座，并就如何编写望远镜应用程序举行研讨会。

This proposal is to calculate and apply theoretical stellar spectra to stars in globular clusters in the Local Group, in order to quantify the metallicity calibration and to investigate the occurrence of variations in the relative abundances of light elements and in the mean stellar age. The work will be based on models and spectra generated from the newly expanded line list of Kurucz, which have reproduced both flux distributions and individual line strengths of the Sun and the cool giant Arcturus in the solar neighborhood. The first stage of the proposed work will be to calculate models and spectra for individual cool giants in the Galactic globular clusters M4, M71, and 47 Tucanae; the open cluster M67; and the Galactic bulge. The goal is to determine the overall metallicity and the abundance ratio of the light elements oxygen, magnesium, silicon, calcium, sodium, and aluminum with respect to iron, to show to what extent explosive nucleosynthesis dominated the element production in various environments and epochs. Following this, theoretical spectra will be completed for hotter stars of various metallicities near that of the Sun, both with and without light element enhancements. Combinations of these spectra appropriate to clusters of different ages will then be compared to the observed integrated-light spectra of globular clusters in Andromeda to simultaneously estimate the iron and light-element abundances and the mean stellar age. The proposed research represents "state of the art" work in stellar atmospheres and elemental abundances, which could make substantial advances in our understanding of the composition and evolution of the Galaxy, namely structure of stars and history of the evolution of the elements. The project furthers VPW program objectives to provide opportunities for women to advance their careers in science or engineering through research, and to encourage other women to pursue careers in these areas through the investigators' enhanced visibility as role models on the host campuses. In this effort, the proposed activities which contribute to the second objective include: giving guest lectures on the real-life analyses of stellar abundances in a graduate course on stellar atmospheres and presenting a seminar on how telescope applications should be written.