Chemical Abundances of M-dwarfs from the APOGEE Survey. I. The Exoplanet Hosting Stars Kepler-138 and Kepler-186

February 2017 • 2017ApJ...835..239S

Authors • Souto, D. • Cunha, K. • García-Hernández, D. A. • Zamora, O. • Allende Prieto, C. • Smith, V. V. • Mahadevan, S. • Blake, C. • Johnson, J. A. • Jönsson, H. • Pinsonneault, M. • Holtzman, J. • Majewski, S. R. • Shetrone, M. • Teske, J. • Nidever, D. • Schiavon, R. • Sobeck, J. • García Pérez, A. E. • Gómez Maqueo Chew, Y. • Stassun, K.

Abstract • We report the first detailed chemical abundance analysis of the exoplanet-hosting M-dwarf stars Kepler-138 and Kepler-186 from the analysis of high-resolution (R ∼ 22,500) H-band spectra from the SDSS-IV-APOGEE survey. Chemical abundances of 13 elements—C, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe—are extracted from the APOGEE spectra of these early M-dwarfs via spectrum syntheses computed with an improved line list that takes into account H₂O and FeH lines. This paper demonstrates that APOGEE spectra can be analyzed to determine detailed chemical compositions of M-dwarfs. Both exoplanet-hosting M-dwarfs display modest sub-solar metallicities: [Fe/H]_Kepler-138 = -0.09 ± 0.09 dex and [Fe/H]_Kepler-186 = -0.08 ± 0.10 dex. The measured metallicities resulting from this high-resolution analysis are found to be higher by ∼0.1-0.2 dex than previous estimates from lower-resolution spectra. The C/O ratios obtained for the two planet-hosting stars are near-solar, with values of 0.55 ± 0.10 for Kepler-138 and 0.52 ± 0.12 for Kepler-186. Kepler-186 exhibits a marginally enhanced [Si/Fe] ratio.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2017ApJ...835..239S
• PDF https://iopscience.iop.org/article/10.3847/1538-4357/835/2/239/pdf
• PDF https://stacks.iop.org/0004-637X/835/239/pdf
• PREPRINT http://arxiv.org/abs/1612.01598
• DATA https://irsa.ipac.caltech.edu/bibdata/2017/S/2017ApJ...835..239S.html
• ELECTR https://doi.org/10.3847%2F1538-4357%2F835%2F2%2F239