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

Souto, D, Cunha, K, Garcia-Hernandez, DA, Zamora, O, Allende Prieto, C, Smith, VV, Mahadevan, S, Blake, C, Johnson, JA, Jonsson, H, Pinsonneault, M, Holtzman, J, Majewski, SR, Shetrone, M, Teske, J, Nidever, D, Schiavon, RP, Sobeck, J, Garcia Perez, AE, Gomez Maqueo Chew, Y and Stassun, K (2017) Chemical Abundances of M-Dwarfs from the Apogee Survey. I. The Exoplanet Hosting Stars Kepler-138 and Kepler-186. Astrophysical Journal, 835 (2). ISSN 0004-637X

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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 subsolar 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.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
Related URLs:
Date Deposited: 05 Feb 2018 10:12
Last Modified: 05 Feb 2018 10:12
DOI or Identification number: 10.3847/1538-4357/835/2/239
URI: http://researchonline.ljmu.ac.uk/id/eprint/7938

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