Standardization of the Solar-Neighborhood Main Sequence for Spectral Types K4 to M6

We have selected a set of nearby stars suitable for use in defining the solar-neighborhood main sequence from type K4 V to M6 V. The chosen stars have excellent photometry, spectral classifications on a consistent scale, and smooth distributions in color and molecular band strength. They also have high-quality parallax measurements which show them to lie near the mean main sequence as defined by a larger sample of stars. High-velocity stars, subdwarfs, and other peculiar types have been avoided, as have close visual binaries which may be difficult to observe separately. We show color-magnitude diagrams for the selected standard stage and for a larger set of stars for which the same data are available.