Volume 635, March 2020
|Number of page(s)||10|
|Published online||01 April 2020|
Impact of the convective mixing-length parameter α on stellar metallicity
Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences,
20A Datun Road,
Beijing 100101, PR China
e-mail: firstname.lastname@example.org; email@example.com
2 School of Astronomy and Space Science, University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, PR China
3 Institute of Astronomy, Russian Academy of Sciences, 119017 Moscow, Russia
4 Universitäts Sternwarte Mümchen, Scheinerstr. 1, 81679 Müchen, Germany
5 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr., 85748 Garching, Germany
Accepted: 16 February 2020
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.
Key words: stars: atmospheres / stars: abundances / stars: fundamental parameters / convection / line: profiles
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.