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Impact of the convective mixing-length parameter α on stellar metallicity

MPG-Autoren
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Wang,  L.
Optical and Interpretative Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Grupp,  F.
Optical and Interpretative Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Zitation

Song, N., Alexeeva, S., Sitnova, T., Wang, L., Grupp, F., & Zhao, G. (2020). Impact of the convective mixing-length parameter α on stellar metallicity. Astronomy and Astrophysics, 635: A176. doi:10.1051/0004-6361/201937110.


Zitierlink: https://hdl.handle.net/21.11116/0000-0006-8D9A-E
Zusammenfassung
Context. Mixing-length theory is used to treat stellar convection. As a simulation in one-dimensional stellar atmospheres models, the mixing-length parameter α is calibrated from the Sun and then applied to other stars. However, there is no strong evidence to suggest that α should be the same for stars of different evolutionary stages.
Aims. We evaluate the impact of the α value on the metallicity of different types of stars and investigate the correlation between the metallicity discrepancy (Δ[Fe∕H]) and stellar parameters (Teff, log g). Methods. We selected ten well-studied field stars and one open cluster of nine members for which high-resolution and high signal-to-noise spectra are available. The model atmospheres were calculated with the code MAFAGS-OS. We derived iron abundances from Fe I and Fe II lines both under local thermodynamic equilibrium and non-LTE conditions using a spectrum synthesis method. After deriving [Fe/H] for each line, we calculated Δ[Fe∕H] with two different α values, fixed solar-calibrated α, and α obtained for each star individually. Finally, we investigated the correlation between Δ[Fe∕H] caused by revised α with stellar parameters.
Results. For FGK dwarf stars, the Δ[Fe∕H] caused by the α correction is less than 0.02 dex, while for turn-off and giant stars, the Δ[Fe∕H] values are no more than 0.03 dex, which are lower than typical uncertainties in metallicity. For main-sequence stars, Δ[Fe∕H] versus Teff and Δ[Fe∕H] versus log g are well fit by linear relations.