Astrometric study of the relative motion of three stars with possible invisible companions based on homogeneous series obtained at Pulkovo with a 26-inch refractor

Abstract

We investigate the relative motion of three stars, ADS 7446, 9346, and 9701, based on long- term observations with the Pulkovo 26-inch refractor. The relative motion of all three stars shows a perturbation that could be produced by the gravitational influence of an invisible companion. For ADS 7446, we have determined the orbit of the photocenter with a period of 7.9 yr; the mass of the companion is more than 0.4M� . For ADS 9346, we have determined the radial velocities of the components: −14.60 km s −1 for A and −13.94 km s −1 for B. For ADS 9346 and 9701, we have determined the dynamical parallaxes, 24 and 20 mas, respectively, which are larger than those in the Hipparcos catalog by 5 mas, and calculated the orbits by the apparent motion parameter (AMP) method. The new orbit of ADS 9346 is: a =5 . 2, P = 2035 yr, and e =0 .46 at the system's mass M =2 .5M� . The new orbits of ADS 9701 are: (a =2 . 9, P = 829 yr, e =0 .54, M =4 .3M� )a nd (a =3 .8, P = 1157 yr, e =0 .53, M =5 .0M� ).