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Abundance patterns among very metal-poor stars in the halo of the Galaxy: a statistical approach

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Author(s):
Vinicius Moris Placco
Total Authors: 1
Document type: Master's Dissertation
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD)
Defense date:
Examining board members:
Silvia Cristina Fernandes Rossi; Beatriz Leonor Silveira Barbuy; Katia Maria Leite da Cunha
Advisor: Silvia Cristina Fernandes Rossi
Abstract

One of the most challenging subjects of Astrophysics is trying to understand the complexity of the chemical composition of stellar objects. Spectroscopic observations are widely used nowadays in order to achieve these goals, as they provide the chemical composition of the atmosphere of the stars. Elements with atomic masses above A>60 are formed by the so called neutron capture processes (r-process and s-process). Its presence on low-mass star spectra (which have long life-time) and low metal content suggests episodes of enrichment by high-mass stars that took place in the early times in the Galaxy formation. Then, the study of those \"metal-poor\" stars enriched by neutron-capture elements may help reproduce the physical conditions of the environment from where they were formed. The main goal of this project is to explore the abundance patterns of the very metal-poor stars observed by the HERES survey. This study allows the analysis of the correlations between chemical elements and place some constraints on the operation of the neutron capture processes in the early Galaxy. This approach made use of statistical tools, such as agglomerative nesting, which can identify the formation of natural groups based on relations among elemental abundances. In this context, this study provides a comprehensive analysis of a 382 metal-poor stars sample, and introduces two new subclasses for metal-poor stars with determined abundances of neutron-capture elements. (AU)

FAPESP's process: 05/01023-8 - Abundance patterns among very metal-poor stars in the halo of the galaxy
Grantee:Vinicius Moris Placco
Support type: Scholarships in Brazil - Master