New binaries in the epsilon Cha association

TL;DR

This study uses adaptive optics speckle observations to identify and analyze binary and multiple star systems in the epsilon Cha association, revealing new binaries and characterizing their properties.

Contribution

First detailed adaptive optics speckle survey of young stars in epsilon Cha, discovering new binaries and providing orbital insights for multiple systems.

Findings

Resolved 10 new binary pairs and 5 known binaries.

Binary frequency for G0 and later stars is comparable to field stars.

All massive stars (A and B types) have companions in the observed range.

Abstract

We present Adaptive Optics-aided speckle observations of 47 young stars in the $\epsilon$ Cha association, made at the 4-m Southern Astrophysical Research Telescope in the $I$-band. We resolved 10 new binary pairs, 5 previously known binaries and two triple systems, also previously known. In the separation range between 4 and 300 AU, the 30 association members of spectral types G0 and later host 6 binary companions, leading to the raw companion frequency of $0.010\pm0.04$ per decade of separation, comparable to the main sequence dwarfs in the field. On the other hand, all 5 massive association members of spectral types A and B have companions in this range. We discuss the newly resolved and known binaries in our sample. Observed motions in the triple system $\epsilon$ Cha, composed of three similar B9V stars, can be described by tentative orbits with periods 13 and $\sim 900$ years, and a large mutual inclination.