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

• Published in: The Astrophysical journal Vol. 835; no. 2; pp. 239 - 250
• Main Authors: Souto, D., Cunha, K., García-Hernández, D. A., Zamora, O., Prieto, C. Allende, 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., Pérez, A. E. García, Chew, Y. Gómez Maqueo, Stassun, K.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.02.2017; IOP Publishing
• Subjects: ABUNDANCE; Aluminum; Astronomi, astrofysik och kosmologi; Astronomy, Astrophysics and Cosmology; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHEMICAL COMPOSITION; Chromium; CONCENTRATION RATIO; DWARF STARS; Extrasolar planets; Fysik; High resolution; infrared: stars; INTERACTIONS; Iron; Magnesium; Manganese; MASS; METALLICITY; Natural Sciences; Naturvetenskap; Organic chemistry; Physical Sciences; planet; planet-star interactions; planetary systems; PLANETS; Polls & surveys; Red dwarf stars; RESOLUTION; Silicon; SPECTRA; star interactions; stars: abundances; stars: fundamental parameters; stars: low-mass; SYNTHESIS; Titanium; WATER
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/835/2/239

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.