EVOLVED GK STARS NEAR THE SUN .1. THE OLD DISK POPULATION

A sample of nearly two thousand GK giants with intermediate band, (R,I), DDO and Geneva photometry has been assembled. Astrometric data is also available for most of the stars. The some 800 members of the old disk population in the sample yield accurate luminosities (from two sources), reddening values and chemical abundances from calibrations of the photometric parameters. Less than one percent of the objects are peculiar in the sense that the flux distribution is abnormal. The peculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+ stars are all spectroscopic binaries, probably with white dwarf companions, whereas the CH- stars are not. A broad absorption band, centered near 3500 angstrom, is found in the CH+ stars whereas the CH- objects have a broad emission feature in the same region. The intensity of these absorptions and emissions are independent of the intensity of abnormal spectral features. Ten percent of the old disk sample have a heavy element abundance from one and a half to three times the solar value. The distribution of the heavy element abundances is nearly a normal one with a peak near solar abundance and ranges three times to one sixth solar. The distribution of the (U, V) velocities is independent of the heavy element abundance and does not appear to be random. Ten percent of the old disk stars show a CN anomaly, equally divided between CN strong and CN weak. Several stars of individual astrometric or astrophysical importance are isolated.