VILNIUS PHOTOMETRY OF THE RED HORIZONTAL-BRANCH STARS IN THE GALACTICTHICK DISK

The photometric observations and three-dimensional classification in t he Vilnius system have been carried out for 13 of the red horizontal b ranch (RHB) stars in the Galactic thick disk identified by Rose (1985) . The photometric spectral types, metallicities [Fe/H], effective temp eratures, surface gravities and absolute magnitudes are determined. Th e age of about 10-12 Gyr is evaluated for this group of stars from com parison with model isochrones, indicating that the age of the thick di sk is intermediate between the disk globular and the oldest open clust ers.