Stellar Characterization of M Dwarfs from the APOGEE Survey: A Calibrator Sample for M-dwarf Metallicities

February 2020 • 2020ApJ...890..133S

Authors • Souto, Diogo • Cunha, Katia • Smith, Verne V. • Allende Prieto, C. • Burgasser, Adam • Covey, Kevin • García-Hernández, D. A. • Holtzman, Jon A. • Johnson, Jennifer A. • Jönsson, Henrik • Mahadevan, Suvrath • Majewski, Steven R. • Masseron, Thomas • Shetrone, Matthew • Rojas-Ayala, Bárbara • Sobeck, Jennifer • Stassun, Keivan G. • Terrien, Ryan • Teske, Johanna • Wanderley, Fábio • Zamora, Olga

Abstract • We present spectroscopic determinations of the effective temperatures, surface gravities, and metallicities for 21 M dwarfs observed at high resolution (R ∼ 22,500) in the H band as part of the Sloan Digital Sky Survey (SDSS)-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. The atmospheric parameters and metallicities are derived from spectral syntheses with 1D LTE plane-parallel MARCS models and the APOGEE atomic/molecular line list, together with up-to-date H2O and FeH molecular line lists. Our sample range in Teff from ∼3200 to 3800 K, where 11 stars are in binary systems with a warmer (FGK) primary, while the other 10 M dwarfs have interferometric radii in the literature. We define an ${M}_{{K}_{S}}$ M K S -radius calibration based on our M-dwarf radii derived from the detailed analysis of APOGEE spectra and Gaia DR2 distances, as well as a mass-radius relation using the spectroscopically derived surface gravities. A comparison of the derived radii with interferometric values from the literature finds that the spectroscopic radii are slightly offset toward smaller values, with Δ = -0.01 ± 0.02 R⋆/R. In addition, the derived M-dwarf masses based upon the radii and surface gravities tend to be slightly smaller (by ∼5%-10%) than masses derived for M-dwarf members of eclipsing binary systems for a given stellar radius. The metallicities derived for the 11 M dwarfs in binary systems, compared to metallicities obtained for their hotter FGK main-sequence primary stars from the literature, show excellent agreement, with a mean difference of [Fe/H](M dwarf - FGK primary) = +0.04 ± 0.18 dex, confirming the APOGEE metallicity scale derived here for M dwarfs.


IPAC Authors

Jennifer Sobek

Associate Scientist