Dynamics and Evolutionary Status of the Young Triple Stellar System, TY CrA

Abstract

The young star TY CrA was known as a close eclipsing binary, which surprisingly appeared circularized but not synchronized. Recently, a third companion orbiting the close pair was detected. The dynamics of this triple system is here investigated. We show that according to pure 3-body dynamics, the TY CrA central binary should be subject to periodic changes related to the so-called Kozai mechanism in cometary dynamics, which should lead to a rapid collision. Adding tidal effects within that binary preserves its stability. We also show that thanks to the combination of tidal effects and 3-body dynamics, the rotation axes of the components of the central binary may by locked in a particular position (within the orbital plane) which might explain the apparent non-synchronism of the binary. Such a situation would not be stable if the central binary was alone, and if the system was older than ~ 107 yrs.