Metallicity and Temperature Indicators in M Dwarf K-band Spectra: Testing New and Updated Calibrations with Observations of 133 Solar Neighborhood M Dwarfs
Abstract
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 H_2O opacity (the H_2O-K_2 index). Using empirical spectral type standards and synthetic models, we calibrate the H_2O-K_2 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 H_2O-K_2 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 H_2O-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.
Additional Information
© 2012 American Astronomical Society. Received 2011 September 6; accepted 2012 January 9; published 2012 March 13. We thank the staff and telescope operators of Palomar Observatory for their support. We thank Travis Barman, John Bochanski, Jeff Valenti, and Andrew West for helpful discussions about various topics. We thank John Johnson for providing the M dwarf targets in the CPS target list for the K-S test calculations. We thank the anonymous referee for her/his helpful comments that improved our manuscript. K.R.C. acknowledges support for this work from the Hubble Fellowship Program, provided by NASA through Hubble Fellowship grant HST-HF-51253.01-A awarded by the STScI, which is operated by the AURA, Inc., for NASA, under contract NAS 5-26555. This research has made use of NASA's Astrophysics Data System Bibliographic Services, the SIMBAD database, operated at CDS, Strasbourg, France, the NASA/IPAC Extragalactic Database, operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and the VizieR database of astronomical catalogs (Ochsenbein et al. 2000). This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Facility: Hale (TSPEC)Attached Files
Published - RojasAyala2012p18033Astrophys_J.pdf
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Additional details
- Eprint ID
- 31363
- Resolver ID
- CaltechAUTHORS:20120508-155158197
- Palomar Observatory
- HST-HF-51253.01-A
- NASA Hubble Fellowship
- NAS 5-26555
- NASA
- Space Telescope Science Institute
- NSF
- Created
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2012-05-09Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field