Nearby stars of the Galactic disk and halo *
Received 11 May 1998 / Accepted 30 June 1998
Model atmosphere analyses of échelle spectra of some fifty nearby F- and G-type stars are presented. The sample is confined to the main-sequence, turnoff and subgiant region, regardless of the metal abundance. On the base of these data, spectroscopic parallaxes are calculated and compared to the Hipparcos astrometry to explore the reliability of the derived stellar parameters, notably the surface gravity and metal abundance scale.
The spectroscopic distance scale is found in good agreement with the Hipparcos parallaxes and is characterized by a 5% rms uncertainty. The results suggest a precision in of dex, and 0.05-0.10 dex for the metallicity. There is also reasonable evidence for the spectroscopic effective temperature scale to be free of systematic errors; typical uncertainties are assessed to K. The basic spectroscopic parameters are supplemented by data for the microturbulence velocities, the projected rotational velocities, stellar radii and -enhancement abundances, the latter represented by the element magnesium. Stellar masses are also given, though many are probably subject to small adjustments (typically 5%) in forthcoming analyses. The well-defined distance correlation is also demonstrated to be an efficient means for an identification of spectroscopic binaries.
The results are discussed in terms of a spectroscopically established distance scale, the sites of the stellar populations in the [Mg/H]-[Fe/Mg] plane, a timescale for the Galactic thin disk, and the potential of future - Kiel diagrams for a precise determination of Galactic globular clusters ages.
Key words: stars: distances stars: fundamental parameters stars: late-type Galaxy: evolution
© European Southern Observatory (ESO) 1998
Online publication: September 8, 1998