Imaging survey of subsystems in secondary components to nearby southern dwarfs

TL;DR

This survey of secondary components in nearby dwarf star systems used adaptive optics and speckle interferometry to evaluate the frequency of subsystems, finding it consistent with that of solar-type stars, supporting a formation by fragmentation.

Contribution

The paper provides new observational data on secondary subsystems in nearby dwarfs, combining imaging and literature data to assess their frequency and implications for star formation theories.

Findings

Detected one new binary with 0.2" separation.

Found secondary subsystem frequency of 0.21+-0.06.

Results support formation by fragmentation rather than dynamical evolution.

Abstract

To improve the statistics of hierarchical multiplicity, secondary components of wide nearby binaries with solar-type primaries were surveyed at the SOAR telescope for evaluating the frequency of subsystems. Images of 17 faint secondaries were obtained with the SOAR Adaptive Module that improved the seeing; one new 0.2" binary was detected. For all targets, photometry in the g', i', z' bands is given. Another 46 secondaries were observed by speckle interferometry, resolving 7 close subsystems. Adding literature data, the binarity of 95 secondary components is evaluated. We found that the detection-corrected frequency of secondary subsystems with periods in the well-surveyed range from 10^3 to 10^5 days is 0.21+-0.06, same as the normal frequency of such binaries among solar-type stars, 0.18. This indicates that wide binaries are unlikely to be produced by dynamical evolution of N-body systems, but are rather formed by fragmentation.