DISK LUMINOSITY FUNCTION BASED ON THE LOWELL PROPER MOTION SURVEY

Disk stellar luminosity function has been derived with stars in the Lowell Proper Motion Survey which contains about 9000 stars with ${\mu}\;{\geq}\;0".27$ of arc/yr, $8\;<\;m_{pg}\;<\;17$ and with bright stars in the Smithsonian Astrophysical Observatory (SAO) Star Catalogue, Luminosity function has been obtained with stars within 20 pc by Luyten's mean absolute magnitudes method using Reduced Proper Motion Diagram to select disk stars. Magnitudes and colors, in the SAO Star Catalogue as well as in the Lowell Proper Motion Survey have been transformed to the UBV system from the published UBV data. It has been found that stars which have higher proper motion than the original limit of the proper motion survey are missed, when the relation between the absolute magnitude and reduced proper motion is applied to sample stars without considering the dispersion in magnitude. Correction factors for missing stars have been estimated according to their limits of proper motion which are dependent on the absolute magnitude. Resulting luminosity function shows Wielen's dip at $M_B{\sim}10$, and systematic enhancement of stars on the average of about ${\Delta}\log\;{\Phi}\;(M_B){\sim}0.2$ compared with Luyten's luminosity function.