Orbits of four young triple-lined multiple systems

Abstract: Each of the nearby triple systems HIP 7601, 13498, 23824, and 113597 (HD 10800, 18198, 35877, 217389) consists of solar-type dwarfs with comparable masses, where all three components are resolved spectrally, while the outer pairs are resolved both visually and spectrally. These stars are relatively young (between 100 and 600 Myr) and chromospherically active (X-ray sources), although they rotate slowly. Spectroscopic orbits of the inner subsystems (periods 19.4, 14.1, 5.6, 20.3 days) and orbits of the outer systems (periods 1.75, 51, 27, 500 yrs, respectively) are determined. For HIP 7601 and 13498, the combined spectro-interferometric outer orbits produce direct measurement of masses of all components, allowing comparison with stellar models. The 6708A lithium line is present and its strength is measured in each component individually by subtracting the contributions of other components. The inner and outer orbits of HIP 7601 are nearly circular, likely co-planar, and have a modest period ratio of 1:33. This study contributes to the characterization of hierarchical multiplicity in the solar neighborhood and provides data for testing stellar evolutionary models and chronology.