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

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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.