RESEARCH
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Determining helium abundances in evolved stars

Guillaume Dréau
Université Paris-Sud / IA

Abstract
The knowledge of the helium abundance in stars is essential to infer their evolution on the HR diagram. However, determining the helium abundance in cool stars, such as red giants, is not an easy task. The analysis of global stellar oscillations offers that opportunity. Here, we use the acoustic modes to characterise the signature of the second helium ionization zone in red giants, from which the abundance of helium may be inferred. The innovation we bring is that in addition to using radial modes, we consider the pure acoustic dipole modes. We find that the addition of these modes to the analysis improves the characterisation of the second helium ionization zone, leading to a more reliable determination of the helium abundance in red giant stars.

2018 July 19, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Classroom)
Rua das Estrelas, 4150-762 Porto

Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia