From binaries to multiples. II. Statistical data

Statistics of hierarchical multiplicity among solar-type dwarfs are studied using the distance-limited sample of 4847 targets presented in the accompanying Paper I. Known facts about binaries (multiplicity fraction 0.46, lognormal period distribution with median period 100yr and logarithmic dispersion 2.4, and nearly uniform mass-ratio distribution independent of the period) are confirmed with a high statistical significance.

The fraction of hierarchies with three or more components is 0.13+/-0.01, and the fractions of targets with n=1,2,3,... components are 54:33:8:4:1. Subsystems in the secondary components are almost as frequent as in the primary components, but in half of such cases both inner pairs are present. The high frequency of those 2+2 hierarchies (4%) suggests that both inner pairs were formed by a common process.