METALLICITY AND TEMPERATURE INDICATORS IN M DWARF K-BAND SPECTRA: TESTING NEW AND UPDATED CALIBRATIONS WITH OBSERVATIONS OF 133 SOLAR NEIGHBORHOOD M DWARFS

By B. Rojas-Ayala, K. Covey, P. Muirhead, J. Lloyd. 2011

241 citations recorded by the source corpus.

We present K-band spectra for 133 nearby (d < 33 ps) M dwarfs, including 18 M dwarfs with reliable metallicity estimates (as inferred from an FGK type companion), 11 M dwarf planet hosts, more than 2/3 of the M dwarfs in the northern 8 pc sample, and several M dwarfs from the LSPM catalog. From these spectra, we measure equivalent widths of the Ca and Na lines, and a spectral index quantifying the absorption due to H2O opacity (the H2O–K2 index). Using empirical spectral type standards and synthetic models, we calibrate the H2O–K2 index as an indicator of an M dwarf's spectral type and effective temperature. We also present a revised relationship that estimates the [Fe/H] and [M/H] metallicities of M dwarfs from their Na i, Ca i, and H2O–K2 measurements. Comparisons to model atmosphere provide a qualitative validation of our approach, but also reveal an overall offset between the atomic line strengths predicted by models as compared to actual observations. Our metallicity estimates also reproduce expected correlations with Galactic space motions and Hα emission line strengths, and return statistically identical metallicities for M dwarfs within a common multiple system. Finally, we find systematic residuals between our H2O-based spectral types and those derived from optical spectral features with previously known sensitivity to stellar metallicity, such as TiO, and identify the CaH1 index as a promising optical index for diagnosing the metallicities of near-solar M dwarfs.

View Paper: https://www.semanticscholar.org/paper/70b6121f33ea9a0c05a15d7618db64d1ee16c0d0

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Citations in the corpus

• SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs - I. New atmospheric parameters and masses for 48 stars with planets (2013, background): “…Önehag et al. 2012), most determinations of their values are based on calibrations using colors (Bonfilset al. 2005a; Johnson & Apps 2009; Casagrande et al. 2008; Schlaufman & Laughlin 2010; Neves et al. 2012) or spectroscopic indices (e.g. Terrien et al. 2012; Rojas-Ayala et al. 2012; Mann t al.”
• SPECTRO-THERMOMETRY OF M DWARFS AND THEIR CANDIDATE PLANETS: TOO HOT, TOO COOL, OR JUST RIGHT? (2013, methodology): “B12 draw metallicities for their K and M dwarfs from Edvardsson et al. (1993), Anderson & Francis (2011), Rojas-Ayala et al. (2012), and Neves et al. (2012).”
• NEAR-INFRARED METALLICITIES, RADIAL VELOCITIES, AND SPECTRAL TYPES FOR 447 NEARBY M DWARFS (2013, background): “Efforts have been made to extend these relations to the lowest stellar masses (e.g. Johnson & Apps 2009; Schlaufman & Laughlin 2010; Rojas-Ayala et al. 2012), but have been limited by the small number of planets currently known around M dwarfs.”
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) — The survey's science plan (2012, background): “…an lysis have revealed patterns which now make it possible to evaluate metallicities (Lepine et al. 2007; Woolfe, Lepine, & Wallerstein 2009; Rojas-Ayala et al. 2012) and identify relatively young (< 500Myr) M dwarfs (West et al. 2008; Schlieder et al. 2012) based on spectral features in…”
• STELLAR DIAMETERS AND TEMPERATURES. II. MAIN-SEQUENCE K- AND M-STARS (2012, methodology): “For this study, we cite the metallicities of M-dwarfs from the calibration presented in Rojas-Ayala et al. (2012), wherever available.”
• THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS (2013, methodology): “Muirhead et al. (2012a) determined effective temperature and metallicity directly from their spectra using the H2O-K2 index (Rojas-Ayala et al. 2012) and then constrain stellar radii and masses using Dartmouth stellar evolutionary models (Dotter et al. 2008; Feiden et al. 2011).”