Astron. J., 128, 463-483 (2004/July-0)
Meeting the cool neighbors. VIII. A preliminary 20 parsec census from the NLTT catalogue.
REID I.N., CRUZ K.L., ALLEN P., MUNGALL F., KILKENNY D., LIEBERT J., HAWLEY S.L., FRASER O.J., COVEY K.R., LOWRANCE P., KIRKPATRICK J.D. and BURGASSER A.J.
Abstract (from CDS):
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.
Galaxy: Stellar Content - Stars: Low-Mass, Brown Dwarfs - Stars: Luminosity Function, Mass Function
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<Available at CDS (J/AJ/128/463): tables 1-8 refs.dat notes.dat>
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