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Title: Prospecting in ultracool dwarfs: measuring the metallicities of mid- and late-M dwarfs

Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. The low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R ∼ 2000) K-band (≅ 2.2 μm) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early-M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early-M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to ∼0.07 dex for M4.5-M9.5 dwarfs with –0.58 < [Fe/H] < +0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolvedmore » binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.« less
Authors:
 [1] ;  [2] ;  [3] ; ; ; ;  [4] ;  [5]
  1. Department of Astronomy, University of Texas at Austin, TX (United States)
  2. Max Planck Institute for Astronomy, Konigstuhl 17, Heidelberg D-69117 (Germany)
  3. Department of Geology and Geophysics, University of Hawai'i, 1680 East-West Road, Honolulu, HI 96822 (United States)
  4. Institute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
  5. Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
Publication Date:
OSTI Identifier:
22340213
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 147; Journal Issue: 6; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ATMOSPHERES; BINARY STARS; CALIBRATION; DWARF STARS; IRON 58; METALLICITY; MOLECULES; RESOLUTION; SPECTRA; SUN