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Description
The young nearby solar-type star HD 91962 is a rare quadruple system where three companions revolve around the main component with periods of 170.3days, 8.85years, and 205years. The two outer orbits are nearly co-planar, and all orbits have small eccentricities. We refine the visual orbit of the outer pair and determine the combined spectro-interferometric orbit of the middle 8.8year pair and the spectroscopic orbit of the inner binary. The middle and inner orbits are likely locked in a 1:19 resonance, and the ratio of the outer and middle periods is ~23. The masses of all components are estimated (inside-out: 1.14, 0.32, 0.64, 0.64 solar mass). The dynamical parallax is 27.4+/-0.6mas. We speculate that this multiple system originated from collapse of an isolated core and that the companions migrated in a dissipative disk. Other multiple systems with similar features (co-planarity, small eccentricity, and period ratio around 20) are known.
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