Multiplicity among solar-type stars.

The paper presents results of a search for spectroscopic binaries among 135 bright field stars of types F3 - G2 IV or V. Orbital elements for 25 newly discovered spectroscopic binaries are derived from radial velocities measured in 20 coude spectra for each star, and velocity curves are also computed for each of these binaries. It is found that the ratios of observed singles:doubles:triples:quadruples among the 135 program stars are 42:46:9:2. The 88 computed and estimated periods show a relatively smooth distribution with a single maximum and a median period of 14 years. It is tentatively suggested that the discovered binaries show no pronounced grouping tendency in age or evolutionary state. The number of binaries not revealed is estimated, the secondary masses for both the observed and undetected binaries are determined statistically, and it is concluded that the short-period binaries are fission systems while the long-period systems are those in which pairs of protostars contracted separately. On the average, the multiple systems are found to be 0.22 magnitude brighter than the primaries alone.