The absolute magnitude of K0V stars from BT HIPPARCOS parallaxes

Abstract

We investigate the properties of K0V stars with Hipparcos parallaxes and spectral types taken from the Michigan Spectral Survey. The sample of 200 objects allows the empirical investigation of the magnitude selection (Malmquist) bias, which appears clearly present. By selecting those objects that are not affected by bias, we find a mean absolute magnitude of M_{_V} = 5.7, a downward revision from 5.9 mag. listed in Schmidt-Kaler (1982). Some objects have absolute magnitudes far brighter than M_{_V} = 5.7, and it is suggested that these objects (~ 20% of the total sample) are K0IV stars which may have been mis-classified as a K0V star. The presence of the Malmquist bias in even this high quality sample suggests that no sample can be expected to be bias-free.