METAL-RICH M-DWARF PLANET HOSTS: METALLICITIES WITH K-BAND SPECTRA
- NASA Earth and Space Science Fellow. (United States)
A metal-rich environment facilitates planet formation, making metal-rich stars the most favorable targets for surveys seeking to detect new exoplanets. Using this advantage to identify likely low-mass planet hosts, however, has been difficult: until now methods to determine M-dwarf metallicities required observationally expensive data (such as parallaxes and high-resolution spectra) and were limited to a few bright cool stars. We have obtained moderate (R {approx} 2700) resolution K-band spectra of 17 M dwarfs with metallicity estimates derived from their FGK companions. Analysis of these spectra, and inspection of theoretical synthetic spectra, reveals that an M dwarf's metallicity can be inferred from the strength of its Na I doublet (2.206 {mu}m and 2.209 {mu}m) and Ca I triplet (2.261 {mu}m, 2.263 {mu}m, and 2.265 {mu}m) absorption lines. We use these features, and a temperature-sensitive water index, to construct an empirical metallicity indicator applicable for M dwarfs with near-solar metallicities (-0.5< [Fe/H] < +0.5). This indicator has an accuracy of {+-}0.15 dex, comparable to that of existing techniques for estimating M-dwarf metallicities, but is more observationally accessible, requiring only a moderate resolution K-band spectrum. Applying this method to eight known M-dwarf planet hosts, we estimate metallicities ([Fe/H]) in excess of the mean metallicity of M dwarfs in the solar neighborhood, consistent with the metallicity distribution of FGK planet hosts.
- OSTI ID:
- 21452834
- Journal Information:
- Astrophysical Journal Letters, Vol. 720, Issue 1; Other Information: DOI: 10.1088/2041-8205/720/1/L113; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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