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        Prospecting in ultracool dwarfs : Measuring the metallicities of mid- and late-m dwarfs

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        1403.5560v2.pdf (PDF, 525Kb)
        Mann_2014_AJ_147_160.pdf (PDF, 712Kb)
        Author
        Mann, Andrew W.
        Deacon, Niall R.
        Gaidos, Eric
        Ansdell, Megan
        Brewer, John M.
        Liu, Michael C.
        Magnier, Eugene A.
        Aller, Kimberly M.
        Attention
        2299/20767
        Abstract
        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 unresolved 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.
        Publication date
        2014-05-14
        Published in
        The Astronomical Journal
        Published version
        https://doi.org/10.1088/0004-6256/147/6/160
        Other links
        http://hdl.handle.net/2299/20767
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