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Title:
Meeting the Cool Neighbors. VIII. A Preliminary 20 Parsec Census from the NLTT Catalogue
Authors:
Reid, I. Neill; Cruz, Kelle L.; Allen, Peter; Mungall, F.; Kilkenny, D.; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.; Covey, Kevin R.; Lowrance, Patrick; Kirkpatrick, J. Davy; Burgasser, Adam J.
Affiliation:
AA(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; and Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 ), AB(Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104; Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.), AC(Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104; Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.), AD(Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104), AE(South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa), AF(Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721), AG(Department of Astronomy, University of Washington, Box 351580, Seattle, WA 28195), AH(Department of Astronomy, University of Washington, Box 351580, Seattle, WA 28195), AI(Department of Astronomy, University of Washington, Box 351580, Seattle, WA 28195), AJ(Infrared Processing and Analysis Center, 100-22, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125; Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.), AK(Infrared Processing and Analysis Center, 100-22, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125), AL(Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1562)
Publication:
The Astronomical Journal, Volume 128, Issue 1, pp. 463-483. (AJ Homepage)
Publication Date:
07/2004
Origin:
UCP
Astronomy Keywords:
Galaxy: Stellar Content, Stars: Low-Mass, Brown Dwarfs, Stars: Luminosity Function, Mass Function
DOI:
10.1086/421374
Bibliographic Code:
2004AJ....128..463R

Abstract

Continuing our census of late-type dwarfs in the solar neighborhood, we present BVRI photometry and optical spectroscopy of 800 mid-type M dwarfs drawn from the NLTT proper-motion catalog. The targets are taken both from our own cross-referencing of the NLTT Catalogue and the 2MASS Second Incremental Data Release, and from the revised NLTT compiled recently by Salim & Gould. All are identified as nearby-star candidates based on their location in the (mr,mr-Ks) diagram. Three hundred stars discussed here have previous astrometric, photometric, or spectroscopic observations. We present new BVRI photometry for 101 stars, together with low-resolution spectroscopy of a further 400 dwarfs. In total, we find that 241 stars are within 20 pc of the Sun, while a further 70 lie within 1 σ of our distance limit. Combining the present results with previous analyses, we have quantitative observations for 1910 of the 1913 candidates in our NLTT nearby-star samples. Eight hundred fifteen of those stars have distance estimates of 20 pc or less, including 312 additions to the local census. With our NLTT follow-up observations essentially complete, we have searched the literature for K and early-type M dwarfs within the sampling volume covered by the 2MASS second release. Comparing the resultant 20 pc census against predicted numbers, derived from the 8 pc luminosity function, shows an overall deficit of ~20% for stellar systems and ~35% for individual stars. Almost all are likely to be fainter than MJ=7, and at least half are probably as yet undiscovered companions of known nearby stars. Our results suggest that there are relatively few missing systems at the lowest luminosities, MJ>8.5. We discuss possible means of identifying the missing stars.

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Part 1     Part  2     Part  3     Part  4     Part  5     Part  6     Part  7     Part  8     Part  9     Part 10    


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