A 3D model for α $\alpha$ Gem AB: orbits and dynamics

Abstract

The well-known multiple star system, Castor, and particularly, the [(Aa, Ab), (Ba, Bb)] subsystem, was studied in detail. After a rigorous analysis of the quality controls, a new solution for the visual orbit yielded new values for the different physical and orbital parameters of the system. In addition, a comprehensive investigation of the orbital configuration of the quadruple system allowed us to provide both accurate individual masses and orbital inclinations of the spectroscopic subcomponents, as well as a new value of its orbital parallax. Finally, by means of a numerical analysis of the long-term dynamics, we obtained the most probable values of the nodal angles of the two spectroscopic subsystems for the first time.Furthermore, the full characterization of this remarkable system allowed us to discuss some interesting features of its present configuration. In this way, we concluded that the eccentric (Aa, Ab) subsystem is yet undergoing Kozai-Lidov cycles whereas, on the contrary, the circular (Ba, Bb) subsystem has probably already reached a stable stage.

The Orbits and Dynamical Masses of the Castor System

“…Noting that the typical separation of the three spectroscopic subsystems from each other is large, Anosova et al (1989) treated Castor as a triple system (A, B, C) for dynamical purposes and showed, based on the limited information then available, that it is gravitationally bound. Subsequent studies, still handicapped by the limited knowledge of many of the orbital properties, have investigated the stability of the various subsystems and the long-term evolution of some of their orbital elements (Beust 2003;Andrade & Docobo 2015;Matvienko et al 2015;Docobo et al 2016). The latter study focused on the possibility that some of the subsystems are undergoing Kozai-Lidov (KL) cycles (Kozai 1962;Lidov 1962), a mechanism that transfers angular momentum between the inner and outer orbits causing oscillations in the inner eccentricities and inclination angles.…”