A SPECTROSCOPIC CATALOG OF THE BRIGHTEST (<i>J</i>&lt; 9) M DWARFS IN THE NORTHERN SKY^,

Abstract

We present a spectroscopic catalog of the 1,564 brightest (J&lt;9) M dwarf\ncandidates in the northern sky, as selected from the SUPERBLINK proper motion\ncatalog. Observations confirm 1,408 of the candidates to be late-K and M dwarfs\nwith spectral subtypes K7-M6. From the low \\mu&gt;40 mas/yr proper motion limit\nand high level of completeness of the SUPERBLINK catalog in that magnitude\nrange, we estimate that our spectroscopic census most likely includes &gt;90% of\nall existing, northern-sky M dwarfs with apparent magnitude J&lt;9. Only 682 stars\nin our sample are listed in the Third Catalog of Nearby Stars (CNS3); most\nothers are relative unknowns and have spectroscopic data presented here for the\nfirst time. Spectral subtypes are assigned based on spectral index measurements\nof CaH and TiO molecular bands. A comparison of spectra from the same stars\nobtained at different observatories however reveals that spectral band index\nmeasurements are dependent on spectral resolution, spectrophotometric\ncalibration, and other instrumental factors. After systematic corrections and a\nrecalibration of the subtype-index relationships, we find that we can\nconsistently and reliably classify all our stars to a half-subtype precision.\nThe use of corrected spectral indices further requires us to recalibrate the\n\\zeta parameter, from which we estimate metallicities +/-0.5dex accuracy in\ndwarfs of subtypes M2 and earlier, and +/-0.2dex accuracy for later (M3-M5)\nsubtypes. Existing geometric parallax measurements are extracted from the\nliterature for 624 stars, and are used to determine spectroscopic and\nphotometric distances for all the other stars. Our catalog will be most useful\nto guide the selection of the best M dwarf targets for exoplanet searches, in\nparticular those using high-precision radial velocity measurements.\n