THE ATMOSPHERIC CHEMICAL-COMPOSITION OF S TARS WITH LARGE PROPER MOTIONS

A sample of stars with large proper motions from the list of Carney et al. [1] is studied as part of a detailed investigation of the chemica l composition of the oldest population of Galactic stars. CCD spectra with signal-to-noise ratio greater than 100 and spectral resolution R approximate to 25 000 have been obtained in the wavelength range 5000- 7200 or 5500-8700 Angstrom for all the objects in the sample on the Ry s' echelle spectrometer of the 6-m telescope of the Special Astrophysi cal Observatory. Atmospheric parameters and the abundances of more tha n 20 chemical elements, including lithium, are determined for the firs t 10 stars in the program using a model atmosphere method and purely s pectral criteria. The stellar radial velocities are determined with ac curacy better than 0.2 km s(-1) using a large set of lines. The result ing set of parameters serves as a basis to determine the evolutionary status of the stars. The sample of stars studied is kinematically unif orm, but is not uniform in its metallicities and radial velocities, an d includes both Population II stars and stars belonging to the young a nd old (thick) disks. It is important to emphasize that spectroscopic determination of the luminosity of the metal-poor stars studied identi fies most of them as halo subgiants and giants rather than unevolved s tars. The problem of determining the primordial lithium abundance from the spectra of unevolved halo stars is discussed.