THE DYNAMICAL STATE AND LONG-TERM STABILITY OF HIP 102589

Abstract

The dynamical state (component masses and kinematic parameters) of the triple star HIP 102589 is redetermined by fitting the simple double two-body model and the accurate three-body model, respectively, to observational data including those accumulated since the last orbit determination in 1992. Though the precision-weighted sum of squared residuals calculated from our results with both models are significantly smaller than the previous ones, only the result with the three-body model is statistically acceptable according to the goodness-of-fit test. The forward and backward long-term dynamical evolutions are numerically explored on the timescale of an estimated age of the components. It is found that the three-body system remains integrated and its hierarchical configuration keeps unchanged since the formation of the components, despite the fact that the instantaneous double two-body orbits vary significantly. This implies that the triple star may not be formed by a three-body encounter. Also, the possibility that the most massive component is itself a tightly bounded binary is discussed based on the redetermined mass and a stellar empirical mass–luminosity relation.