An H-band Spectroscopic Metallicity Calibration for M Dwarfs
Abstract
We present an empirical near-infrared (NIR) spectroscopic method for estimating M dwarf metallicities, based on features in the H band, as well as an implementation of a similar published method in the K band. We obtained R ~ 2000 NIR spectra of a sample of M dwarfs using the NASA IRTF-SpeX spectrograph, including 22 M dwarf metallicity calibration targets that have FGK companions with known metallicities. The H-band and K-band calibrations provide equivalent fits to the metallicities of these binaries, with an accuracy of ±0.12 dex. We derive the first empirically calibrated spectroscopic metallicity estimate for the giant planet-hosting M dwarf GJ 317, confirming its supersolar metallicity. Combining this result with observations of eight other M dwarf planet hosts, we find that M dwarfs with giant planets are preferentially metal-rich compared to those that host less massive planets. Our H-band calibration relies on strongly metallicity-dependent features in the H band, which will be useful in compositional studies using mid- to high-resolution NIR M dwarf spectra, such as those produced by multiplexed surveys like SDSS-III APOGEE. These results will also be immediately useful for ongoing spectroscopic surveys of M dwarfs.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2012
- DOI:
- arXiv:
- arXiv:1202.1800
- Bibcode:
- 2012ApJ...747L..38T
- Keywords:
-
- planetary systems;
- stars: abundances;
- stars: late-type;
- techniques: spectroscopic;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted to ApJ Letters
