Statistics of spectroscopic sub-systems in visual multiple stars^*

¹ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
² Sternberg Astronomical Institute, 13 Universitetsky prosp., 119899 Moscow, Russia e-mail: misha@sai.msu.ru

Corresponding author: A. Tokovinin, atokovinin@ctio.noao.edu

Received: 18 October 2001
Accepted: 6 November 2001

Abstract

A large sample of visual multiples of spectral types F5-M has been surveyed for the presence of spectroscopic sub-systems. Some 4200 radial velocities of 574 components were measured in 1994–2000 with the correlation radial velocity meter. A total of 46 new spectroscopic orbits were computed for this sample. Physical relations are established for most of the visual systems and several optical components are identified as well. The period distribution of sub-systems has a maximum at periods from 2 to 7 days, likely explained by a combination of tidal dissipation with triple-star dynamics. The fraction of spectroscopic sub-systems among the dwarf components of close visual binaries with known orbits is similar to that of field dwarfs, from 11% to 18% per component. Sub-systems are more frequent among the components of wide visual binaries and among wide tertiary components to the known visual or spectroscopic binaries – 20% and 30%, respectively. In triple systems with both outer (visual) and inner (spectroscopic) orbits known, we find an anti-correlation between the periods of inner sub-systems and the eccentricities of outer orbits which must be related to dynamical stability constraints.