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Gravitational settling in solar-like stars: impact of the different ways to estimate [Fe/H] in stellar models

Nuno A. M. Moedas

One of the observational parameters used to constrain stellar models is the surface iron content ([Fe/H]). However, in stellar models, its value is often approximated with the total metallicity ([M/H]). It is estimated using the mass fraction of heavy elements (Z) instead of the iron one. This approx- imation is only valid if the surface abundance variations of iron are the same as the other metals. However, this is not the case because chemical elements are transported at different speeds by micro- scopic transport processes inside stars (i.e. atomic diffusion).
In this work, we used stellar models including atomic diffusion (gravitational settling only) and com- pared the metallicity values obtained with both estimations (using iron or Z). We also quantified how the initial chemical composition of the star can affect the efficiency of the gravitational settling. We conclude that some uncertainties can come from the estimation of [Fe/H] when Z is used instead of the actual iron abundance. We also show that changing the initial chemical composition affects the maximum depletion at the stellar surface predicted by models including gravitational settling.

2021 June 25, 13:30

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