ON THE MASS DISTRIBUTION OF STARS IN THE SOLAR NEIGHBOURHOOD

SUMMARY: The present authors analyse samples consisting of Hipparcos stars. Based on the corresponding HR diagrams they estimate masses of Main-Sequence stars from their visual magnitudes. They nd that already beyond the heliocentric radius of 10 pc the eects of observational selection against K and M dwarfs become rather strong. For this reason the authors are inclined to think that the results concerning this heliocentric sphere appear as realistic, i.e. the fraction of low-mass stars (under half solar mass) is about 50 % and, as a consequence, the mean star mass should be about 0.6 solar masses and Agekyan's factor about 1.2. That stars with masses higher than 5 M are very rare is conrmed also from the data concerning more remote stars. It seems that white dwarfs near the Sun are not too frequent so that their presence cannot aect the main results of the present work signicantly. Key words. Stars: luminosity function, mass function { Hertzsprung-Russell (HR) and C-M diagrams 1