Photoelectric Vilnius Photometry of Hipparcos Turn-Off Region Stars

Abstract

Seven-color photometry in the Vilnius system and photometric classification in terms of spectral type, absolute magnitude and metallicity are presented for 145 Hipparcos stars of the turn-off region, most of which have parallaxes determined to an accuracy of at least 15%. The stars selected for the observing program included those identified kinematically as intermediate between the thin disk and halo, plus a number of weak-lined stars discovered previously from objective prism surveys. The metallicity distribution we find for a kinematically defined sample of possible members of the thick disk has a mean abundance [Fe/H]= --0.3 dex and a dispersion of 0.3 dex. Our data seem to suggest a large age for this intermediate population.