Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances

Robert F. Wilson, Johanna Teske, Steven R. Majewski, Katia Cunha, Verne Smith, Diogo Souto, Chad Bender, Suvrath Mahadevan, Nicholas Troup, Carlos Allende Prieto, Keivan G. Stassun, Michael F. Skrutskie, Andrés Almeida, D. A. García-Hernández, Olga Zamora, Jonathan Brinkmann

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Abstract

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has observed ∼600 transiting exoplanets and exoplanet candidates from Kepler (Kepler Objects of Interest, KOIs), most with ≥18 epochs. The combined multi-epoch spectra are of high signal-to-noise ratio (typically ≥100) and yield precise stellar parameters and chemical abundances. We first confirm the ability of the APOGEE abundance pipeline, ASPCAP, to derive reliable [Fe/H] and effective temperatures for FGK dwarf stars - the primary Kepler host stellar type - by comparing the ASPCAP-derived stellar parameters with those from independent high-resolution spectroscopic characterizations for 221 dwarf stars in the literature. With a sample of 282 close-in (P < 100 days) KOIs observed in the APOGEE KOI goal program, we find a correlation between orbital period and host star [Fe/H] characterized by a critical period, Pcrit = 8.3-4.1+0.1days, below which small exoplanets orbit statistically more metal-enriched host stars. This effect may trace a metallicity dependence of the protoplanetary disk inner radius at the time of planet formation or may be a result of rocky planet ingestion driven by inward planetary migration. We also consider that this may trace a metallicity dependence of the dust sublimation radius, but we find no statistically significant correlation with host and orbital period to support such a claim.

Original languageEnglish (US)
Article number68
JournalAstronomical Journal
Volume155
Issue number2
DOIs
StatePublished - Feb 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Wilson, R. F., Teske, J., Majewski, S. R., Cunha, K., Smith, V., Souto, D., Bender, C., Mahadevan, S., Troup, N., Prieto, C. A., Stassun, K. G., Skrutskie, M. F., Almeida, A., García-Hernández, D. A., Zamora, O., & Brinkmann, J. (2018). Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances. Astronomical Journal, 155(2), [68]. https://doi.org/10.3847/1538-3881/aa9f27