Multiplicity among Solar Type Stars in the Solar Neighbourhood - Part Two - Distribution of the Orbital Elements in an Unbiased Sample

An unbiased sample of 164 primary G-dwarf stars in the solar neighborhood are studied with the aid of 4200 radial velocities obtained during almost 13 yrs. Several present-day distributions of the orbital elements are derived. For systems with M(2)/M(1) above 0.1 in the nearby G-dwarf sample, the following results are obtained: (1) The orbital period distribution is unimodal and can be approximated by a Gaussian-type relation with a median period of 180 yrs. (2) The short binaries are circularized up to orbital periods of about 11 d due to the tidal evolution effects - a result compatible with the mean age of the Galactic disk. (3) The tight binaries not affected by tidal effects (in the range between 11 and 1000 d) may reflect the initial binary formation process, and they have a mean eccentricity of 0.31 +/-0.04. For systems with M(2)/M(1) not greater than 0.1, the proportion of brown dwarf companions among the IAU velocity standards is estimated at 10 percent of the primaries, a value in good agreement with that found in the G-dwarf sample.