A SPECTROSCOPIC CATALOG OF THE BRIGHTEST (J < 9) M DWARFS IN THE NORTHERN SKY,

By S. Lépine, E. Hilton, A. Mann, M. Wilde, B. Rojas-Ayala, Kelle Cruz, E. Gaidos. 2012

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We present a spectroscopic catalog of the 1564 brightest (J < 9) M dwarf candidates in the northern sky, as selected from the SUPERBLINK proper motion catalog. Observations confirm 1408 of the candidates to be late-K and M dwarfs with spectral subtypes K7–M6. From the low (μ > 40 mas yr−1) proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, we estimate that our spectroscopic census most likely includes >90% of all existing, northern-sky M dwarfs with apparent magnitude J < 9. Only 682 stars in our sample are listed in the Third Catalog of Nearby Stars (CNS3); most others are relative unknowns and have spectroscopic data presented here for the first time. Spectral subtypes are assigned based on spectral index measurements of CaH and TiO molecular bands; a comparison of spectra from the same stars obtained at different observatories, however, reveals that spectral band index measurements are dependent on spectral resolution, spectrophotometric calibration, and other instrumental factors. As a result, we find that a consistent classification scheme requires that spectral indices be calibrated and corrected for each observatory/instrument used. After systematic corrections and a recalibration of the subtype-index relationships for the CaH2, CaH3, TiO5, and TiO6 spectral indices, we find that we can consistently and reliably classify all our stars to a half-subtype precision. The use of corrected spectral indices further requires us to recalibrate the ζ parameter, a metallicity indicator based on the ratio of TiO and CaH optical bandheads. However, we find that our ζ values are not sensitive enough to diagnose metallicity variations in dwarfs of subtypes M2 and earlier (±0.5 dex accuracy) and are only marginally useful at later M3–M5 subtypes (±0.2 dex accuracy). Fits of our spectra to the Phoenix atmospheric model grid are used to estimate effective temperatures. These suggest the existence of a plateau in the M1–M3 subtype range, in agreement with model fits of infrared spectra but at odds with photometric determinations of Teff. Existing geometric parallax measurements are extracted from the literature for 624 stars, and are used to determine spectroscopic and photometric distances for all the other stars. Active dwarfs are identified from measurements of Hα equivalent widths, and we find a strong correlation between Hα emission in M dwarfs and detected X-ray emission from ROSAT and/or a large UV excess in the GALEX point source catalog. We combine proper motion data and photometric distances to evaluate the (U, V, W) distribution in velocity space, which is found to correlate tightly with the velocity distribution of G dwarfs in the solar neighborhood. However, active stars show a smaller dispersion in their space velocities, which is consistent with those stars being younger on average. Our catalog will be most useful to guide the selection of the best M dwarf targets for exoplanet searches, in particular those using high-precision radial velocity measurements.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/cb801d76321b34fecc49b07710fd52dfdbcdb954

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Citations in the corpus

PROSPECTING IN LATE-TYPE DWARFS: A CALIBRATION OF INFRARED AND VISIBLE SPECTROSCOPIC METALLICITIES OF LATE K AND M DWARFS SPANNING 1.5 dex (2012, methodology): “Further, we do not allow high order terms, while ζ generally requires 3rd or 4th order polynomials of the CaH index (e.g. Lépine et al. 2013).”
SPECTRO-THERMOMETRY OF M DWARFS AND THEIR CANDIDATE PLANETS: TOO HOT, TOO COOL, OR JUST RIGHT? (2013, methodology): “We replace these regions using the best-fit PHOENIX BT-SETTL model atmosphere (Allard et al. 2011) following the procedure described in Mann et al. (2013b) and Lépine et al. (2013), and summarized in Section 5.1.”
BANYAN. XI. The BANYAN Σ Multivariate Bayesian Algorithm to Identify Members of Young Associations with 150 pc (2018, unknown): “…et al. 2014; (16) Malo et al. 2014; (17) Zacharias et al. 2010; (18) van Altena et al. 1995; (19) Houk & Swift 1999; (20) Perryman et al. 1998; (21) Lépine et al. 2013; (22) Wilson 1953; (23) White et al. 2007; (24) Griffin et al. 1988; (25) Cayrel de Strobel et al. 2001; (26) Stephenson…”
SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION (2016, methodology): “We also estimate the spectral type of K2-18 from our SpeX spectrum using the molecular index based methods of Lépine et al. (2013) (TiO5, CaH3) and Rojas-Ayala et al. (2012) (H2O−K2).”
CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS (2015, result): “3 PMSU, Shk10 3.5 3.5 3.0 3.0 3.0 4.0 3.5 M3.”
A NEARBY M STAR WITH THREE TRANSITING SUPER-EARTHS DISCOVERED BY K2 (2015, methodology): “Following the most recent spectral type calibrations of these indices by Lépine et al. (2013), our EFOSC spectrum yields a spectral type of K7.”
Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, methodology): “J > 2.7 that were spectoscopically confirmed as M dwarfs in Lépine et al. (2013).”
HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS (2015, methodology): “Our part of the reduction is described in some detail in Lépine et al. (2013) and Gaidos et al. (2014).”
They are small worlds after all: revised properties of Kepler M dwarf stars and their planets (2015, background): “Proper motions surveys of M dwarfs in the northern sky are nearly complete to this magnitude limit (Lépine & Gaidos 2011; Lépine et al. 2013; Gaidos et al. 2014) and the choice of prior for brighter stars is less critical as long as it is reasonably finite, thus we fix the mean value at its J =…”