An astrometric study of the triple star ADS 48

Abstract

We analyze the series of relative positions of the hierarchical triple system ADS 48 ABF (AB=6″, AF=327″) obtained with the 26-inch Pulkovo refractor during 1961–1995 and measured with the Fantazia automated measuring system. A new relative orbit of pair AB is determined by the method of apparent-motion parameters using new observations and all the available astrometric and astrophysical data on this star, including its Hipparcos parallax. The new orbit for pair AB is reliably reconciled with all the new and previous observations of this star for the sum of the components’ masses equal to \(1.4\mathfrak{M}_ \odot \). The Pulkovo observations (1961–1995) revealed a perturbation with a period of 15 years and an amplitude ρ ∼ 0.″01, suggesting the presence of an unseen companion with a mass as large as \(0.05\mathfrak{M}_ \odot \). Since the oscillation amplitude is at a noise level, the orbit of the suspected companion cannot be determined. Assuming that stars A and B have the same mass, which corresponds to astrophysical data, we computed the parameters of apparent motion of component F relative to the center of mass of system AB and determined the family of orbits that satisfied the Pulkovo observations. All the computed orbits are steeply (more than 55°) inclined to the orbital plane of AB. The orbital motion of star F has been investigated for the first time.