It's Elementary: Chemical Compositions and Characterization of Exoplanet-hosting M-dwarfs using APOGEE
Abstract
Science Goals and Objectives: The determination of accurate physical parameters for stars which host exoplanets is a crucial step in characterizing the size and nature of the planets themselves; one can only know the planet to the level that the host star is known. This program will carry out a detailed spectral analysis for samples of both field M-dwarf stars, along with planet-hosting M-dwarfs uncovered by the Kepler mission, and in particular those hosting multiple small planets (either Earth-size or "super-Earth" size). High-resolution near-infrared spectra will be analyzed using new model atmospheres and analysis techniques pioneered here. The focus of this proposal is both to derive accurate stellar parameters and metallicities, as well pioneer the study of detailed quantitative chemical analyses of 15 key elements in cool M-dwarfs that cannot be obtained from optical spectroscopy. The Kepler mission M-dwarfs are an important component in both transit and radial-velocity searches for exoplanets, thanks to the enhanced detectability of small planets due to the low stellar masses of M-dwarfs, their low luminosities, and small stellar radii. In addition, M-dwarfs are the most numerous stars in the Galaxy. As the extended Kepler mission (K2) uncovers new M-dwarf planet-hosting stars, this project will continue to target strategic subsets of newly identified exoplanet-hosting M-dwarfs in future years. Methodology: Our group has developed accurate and efficient techniques for chemically analyzing cool red giants in the near-infrared H-band (e.g., Smith et al. 2013, ApJ, 765, 16; Cunha et al. 2015, ApJL, 798, 41) as a result of our participation in the SDSS III APOGEE and SDSS IV APOGEE-2 (Apache Point Observatory Galactic Evolution Experiment) Surveys. We are currently conducting an Ancillary Science Program for APOGEE-2 to target all exoplanet-hosting M-dwarfs in the Kepler field and will develop the techniques necessary to use the APOGEE analysis tools to include M-dwarfs in an effective and efficient manner. As additional Extended Kepler Mission (K2) M-dwarf hosts are uncovered, we will target these in the future (APOGEE-2 runs through 2020). Relevance to Exoplanet Research: The proposers here have the expertise in stellar abundance analysis and are well positioned to provide the first high-resolution NIR spectroscopic stellar parameter and abundance analyses of confirmed Kepler M-dwarf small-planet systems. Possible connections between host-star characteristics, such as mass or chemical composition, and the underlying nature of daughter planetary systems, such as masses or even orbital architectures, will be extended to the regime of the Mdwarfs. Low-resolution spectroscopic analyses of M-dwarfs can provide overall estimates of stellar parameters, but these cannot provide the detailed chemical abundance signatures which can be analyzed in high-resolution APOGEE spectra, such as individual C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, Mn, Fe, or Ni abundances, some of which play fundamental roles in planet formation. This project opens a new window into a major class of stars, whose significance as planet hosts will play an increasingly important role in the future, such as representing a large fraction of targets for the TESS mission.
- Publication:
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NASA Proposal id.16-XPR16-4
- Pub Date:
- 2016
- Bibcode:
- 2016xrp..prop....4S