The lower main sequence of stars in the solar neighborhood: Model
  predictions versus observation
  We have used the Simbad database and VizieR catalogue access tools to
construct the observational color-absolute magnitude diagrams of nearby K-M
dwarfs with precise Hipparcos parallaxes (\sigma_\pi/\pi < 0.05). Particular
attention has been paid to removing unresolved double/multiple and variable
stars. In addition to archival data, we have made use of nearly 2000 new
radial-velocity measurements of K-M dwarfs to identify spectroscopic binary
candidates. The main sequences, cleaned from unresolved binaries, variable
stars, and old population stars which can also widen the sequence due to their
presumably lower metallicity, were compared to available solar-metallicity
models. Significant ofsets of most of the model main-sequence lines are seen
with respect to observational data, especially for the lower-mass stars. Only
the location and slope of the Victoria-Regina and, partly, BaSTI isochrones
match the data quite well.
