Orbits of subsystems in four hierarchical multiple stars (1604.06399v1)

Abstract: Seven spectroscopic orbits in nearby solar-type multiple stars are presented. The primary of the chromospherically active star HIP 9642 is a 4.8-day double-lined pair; the outer 420-yr visual orbit is updated, but remains poorly constrained. HIP 12780 is a quadruple system consisting of the resolved 6.7-yr pair FIN 379 Aa,Ab, for which the combined orbit, masses, and orbital parallax are determined here, and the single-lined binary Ba,Bb with a period of 27.8 days. HIP 28790 is a young quintuple system composed of two close binaries Aa,Ab and Ba,Bb with periods of 221 and 13 days, respectively, and a single distant component C. Its subsystem Ba,Bb is peculiar, having the spectroscopic mass ratio of 0.89 but a magnitude difference of ~2.2 mag. HIP 64478 also contains five stars: the A-component is a 29-year visual pair with a previously known 4-day twin subsystem, while the B-component is a contact binary with a period of 5.8 hours, seen nearly pole-on.