PROSPECTING IN LATE-TYPE DWARFS: A CALIBRATION OF INFRARED AND VISIBLE SPECTROSCOPIC METALLICITIES OF LATE K AND M DWARFS SPANNING 1.5 dex

By A. Mann, J. Brewer, E. Gaidos, S. Lépine, E. Hilton. 2012

156 citations recorded by the source corpus.

Knowledge of late K and M dwarf metallicities can be used to guide planet searches and constrain planet formation models. However, the determination of metallicities of late-type stars is difficult because visible wavelength spectra of their cool atmospheres contain many overlapping absorption lines, preventing the measurement of equivalent widths. We present new methods, and improved calibrations of existing methods, to determine metallicities of late K and M dwarfs from moderate resolution (1300 < R < 2000) visible and infrared spectra. We select a sample of 112 wide binary systems that contain a late-type companion to a solar-type primary star. Our sample includes 62 primary stars with previously published metallicities, as well as 50 stars with metallicities determined from our own observations. We use our sample to empirically determine which features in the spectrum of the companion are best correlated with the metallicity of the primary. We find ≃120 features in K and M dwarf spectra that are useful for predicting metallicity. We derive metallicity calibrations for different wavelength ranges, and show that it is possible to get metallicities reliable to <0.10 dex using either visible, J-, H-, or K-band spectra. We find that the most accurate metallicities derived from visible spectra requires the use of different calibrations for early-type (K5.5–M2) and late-type (M2–M6) dwarfs. Our calibrations are applicable to dwarfs with metallicities of −1.04 < [Fe/H] <+0.56 and spectral types from K7 to M5. Lastly, we use our sample of wide binaries to test and refine existing calibrations to determine M dwarf metallicities. We find that the ζ parameter, which measures the ratio of TiO can CaH bands, is correlated with [Fe/H] for super-solar metallicities, and ζ does not always correctly identify metal-poor M dwarfs. We also find that existing calibrations in the K and H bands are quite reliable for stars with [Fe/H] >−0.5, but are less useful for more metal-poor stars.

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

1. A. Mann
2. E. Gaidos
3. D. Charbonneau
4. E. Petigura
5. Timothy Morton
6. C. Dressing
7. E. Newton
8. J. Johnson

Citations in the corpus

• STELLAR AND PLANETARY PROPERTIES OF K2 CAMPAIGN 1 CANDIDATES AND VALIDATION OF 17 PLANETS, INCLUDING A PLANET RECEIVING EARTH-LIKE INSOLATION (2015, methodology): “Metallcity was determined using the procedures from Mann et al. (2013a), in which the authors provide empirical relations between atomic features and M dwarf metallicity, calibrated using wide binaries.”
• AN EMPIRICAL CALIBRATION TO ESTIMATE COOL DWARF FUNDAMENTAL PARAMETERS FROM H-BAND SPECTRA (2014, methodology): “For stars withlogL/L⊙ > −1.75, we use the Mann et al. (2013a) relation, for which the calibration was dominated by early M dwarfs.”
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library (2017, methodology): “The analysis used empirical relations between spectral feature widths and [Fe/H] from Mann et al. (2013) and Mann et al. (2014) to obtain the stellar metallicities.”
• CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS (2015, background): “2012; Mann et al. 2014; Newton et al. 2014), or in both wavelength ranges (Mann et al. 2013, 2015).”
• SPECTRO-THERMOMETRY OF M DWARFS AND THEIR CANDIDATE PLANETS: TOO HOT, TOO COOL, OR JUST RIGHT? (2013, methodology): “We calculate the metallicity of each star using the weighted mean from each of the four calibrations, accounting for both measurement errors and systematic errors in the calibration as reported by Mann et al. (2013a).”
• SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION (2016, methodology): “Based on the SpeX spectrum, we estimate the stellar metallicity using empirical methods based on the spectroscopic indices and equivalent widths calibrated using M dwarfs that have wide, co-moving FGK companions with well determined [Fe/H] (Boyajian et al. 2012; Mann et al. 2013a).”
• Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, methodology): “This was done because the Mann et al. (2013a) calibration utilizes at least one feature blueward of 4800Å, which is only covered by our SNIFS spectra, and because the calibration of Mann et al. (2013a) was itself derived from SNIFS spectra.”
• HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS (2015, methodology): “Mann et al. (2013a, 2014) provide relations between the equivalent widths of atomic features (e.g., Na, Ca) in NIR spectra and the metallicity of the star, calibrated using wide binaries with an FGK primary and an M dwarf companion.”
• NEAR-INFRARED METALLICITIES, RADIAL VELOCITIES, AND SPECTRAL TYPES FOR 447 NEARBY M DWARFS (2013, methodology): “Mann et al. (2013) expanded the sample of calibrators and identified over 100 metal-sensitive features in the NIR and optical.”
• A NEARBY M STAR WITH THREE TRANSITING SUPER-EARTHS DISCOVERED BY K2 (2015, methodology): “Following the suggestion of Mann et al. (2013a), we also discard the J-band metallicity, which is often an outlier.”