From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs
Abstract
Statistics of hierarchical multiplicity among solartype dwarfs are studied using the distancelimited sample of 4847 targets presented in the accompanying Paper I. Known facts about binaries (multiplicity fraction 0.46, lognormal period distribution with median period 100 yr and logarithmic dispersion 2.4, and nearly uniform massratio 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. The statistics of hierarchies can be reproduced by simulations, assuming that the field is a mixture coming from binaryrich and binarypoor environments. Periods of the outer and inner binaries are selected recursively from the same lognormal distribution, subject to the stability constraint and accounting for the correlation between inner subsystems. The simulator can be used to evaluate the frequency of multiple systems with specified parameters. However, it does not reproduce the observed excess of inner periods shorter than 10 days, caused by tidal evolution.
 Publication:

The Astronomical Journal
 Pub Date:
 April 2014
 DOI:
 10.1088/00046256/147/4/87
 arXiv:
 arXiv:1401.6827
 Bibcode:
 2014AJ....147...87T
 Keywords:

 binaries: general;
 stars: solartype;
 stars: statistics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 Accepted by AJ. 14 pages, 14 figures. Table is available at http://www.ctio.noao.edu/~atokovin/papers/multiplestables.tar.gz