The Properties of Main-Sequence Stars from HIPPARCOS Data

We received a sample of 6840 Hipparcos stars south of declination -26 deg that (i) have MK spectral types in the Michigan catalogues and (ii) had spectroscopic parallaxes that placed them within 80 pc of the Sun. Of these, 3727 are well determined as luminosity class V and actually lie within 100 pc. From this subsample we can determine the distribution in M_V of main-sequence stars of given spectral type for spectral types that range from early F to early K. These distributions are significantly non-Gaussian, but when fitted to Gaussians they yield central values of M_V in good agreement with earlier estimates of the absolute magnitudes of main-sequence stars. We also determine anew the distribution of B-V at each spectral type. We find that the dispersion in B-V at given spectral type is very small.