Differential abundances in metal-poor stars: impact in the study of the Galaxy, stellar evolution and Big Bang nucleosynthesis
Henrique Marques Reggiani
mostramos o desenvolvimento de um modelo atômico para estudar a formação das linhas espectroscópicas de potássio, e a aplicação deste modelo no estudo da evolução química do elemento, mostrando que, possivelmente, estrelas massivas em alta rotação podem ser uma importante fonte nucleossintética de potássio. Abstract This thesis presents the main results of the studies developed during the PhD at the Instituto de Astronomia, Geofísica e Ciências Atmosféricas, of the Universidade de São Paulo,
... t resulted in four papers as the first author and one peer-reviewed proceeding. All papers are attached in Appendix A. The main interest throughout the PhD is to study the Formation and early Chemical Evolution of the Galaxy via precise chemical abundances of the metal-poor component of the Galactic inner halo. We explored the viability of a chemical analysis via line-by-line differential abundance analysis in low metallicity stars, and showed that the increased precision might reveal small differences and inhomogeneities that can not be seen in a regular spectroscopic analysis. For this, we employed extremely high-resolution, and high S/N spectra, and we also showed how the quality of our data influences the final abundance precision. The line-by-line differential abundance technique was employed in a larger sample of high-resolution, high S/N, spectra, to study the formation of the inner halo and put constraints on chemical evolution models and the nucleosynthesis processes therein. As byproduct of our analysis, we studied binary stellar evolution through Blue Straggler Stars, which were used to constrain both nucleosynthesis in AGB stars and Blue Straggler formation. We also present the results of a study focused on a pair of binary stars with implications for the formation of the inner halo and the use of chemical tagging to constrain the birth environment of the stars. As a byproduct of this analysis we found implications of possible planetary formation in metal-poor stars. At last, we show the development of an atomic model for a non-LTE analysis of potassium line formation, and its application for the study of the chemical evolution of potassium through cosmic history, with implications for the nucleosynthesis of potassium and Galactic chemical evolution models with yields from massive rotating stars.