Photocentric orbits from a direct combination of ground-based astrometry with Hipparcos II. Preliminary orbits for six astrometric binaries

TL;DR

This paper combines ground-based astrometry with Hipparcos data to calculate preliminary orbits and component masses for six binary star systems, many of which had no previous orbit data, enhancing understanding of their dynamics.

Contribution

It introduces a method for directly combining ground-based and Hipparcos astrometry to derive orbits and masses for binaries lacking prior orbital solutions.

Findings

Preliminary orbits and masses for six binaries were determined.

Identified a possible new component in Mizar A, potentially a dwarf pair.

Enhanced orbital data for systems with no previous calculations.

Abstract

Based on a direct combination of the Hipparcos data with astrometric ground-based observational catalogues having epochs between 1938 and 1999 the preliminary orbits and component masses are calculated for 6 binaries with no previous orbit calculation: $\iota$~Vir (HIP~69701) with period of 55 years, photocentric semi-major axis of 200 mas, relative semi-major axis of 830 mas and a dwarf secondary of 0.6 solar masses; $\gamma$~UMa (HIP~58001) -- 20.5 years, 90 mas, 460 mas and a dwarf secondary of 0.8 solar masses; $\kappa$~Del (HIP~101916) -- 45 years, 100 mas, 520 mas and a dwarf secondary of 0.4 solar masses; 20~Oph (HIP~82369) -- 35.5 years, 140 mas, 460 mas and a dwarf secondary of 0.8 solar masses; $\mu$~Ser (HIP~77516) -- 36 years, 110 mas, 350 mas and a secondary of 2.3 solar masses; as well as a possible new component of Mizar~A ($\zeta$~UMa, HIP~65378) -- 36.5 years, 180 mas, 780 mas, 1.5 solar masses. The latter may be a pair of dwarfs.