The Coordination of Space and Ground-Based Parallax Programs for Improvement of the Stellar Luminosity Function

Abstract

Recent studies have shown that the general stellar luminosity function does not increase monotonically with decreasing luminosity (or mass) but reaches a maximum at an absolute magnitude of about +6 or nearly one solar mass, and a minimum at slightly fainter values, near one-half solar mass. It has been customary for investigators to adopt the smoothed function of Luyten which increases steadily throughout this range of absolute magnitude. However, the dip in the function between absolute magnitudes of about +6 to +9, found long ago by van Rhijn, has recently been reconfirmed by Wielen (1974) from an analysis of the Catalogue of Nearby Stars of Gliese (1969). Lately, Upgren and Armandroff (1981) have investigated the nearby stars listed in Gliese’s catalogue and its recent supplement (Gliese and Jahreiss 1979). They found that all main sequence stars brighter than M_V = +9 (spectral class dM0) as well as the giants and subgiants are uniformly distributed throughout the volume of space within the limiting distance of 22 pc from the Sun. They were able to conclude for several reasons that no statistically significant number of these stars within 22 pc remain to be discovered or identified; thus, the nearby stellar sample is complete and the Wielen function is correct. However, incompleteness becomes very significant for the dwarf M stars, even those just fainter than M_V = +9. Since most of the details of this study have been published (Upgren and Armandroff 1981), no further discussion will be given here.