Description
We examined the statistics of an angle gamma between the radius vector of a visual companion of a multiple star and the vector of its apparent relative motion in the system. We found that for the wide physical subsystems of the 174 objects from the Multiple Star Catalogue (MSC, Cat. <J/A+AS/124/75>) gamma is bell-shaped. Table 1 presents the separation and position angle of visual outer companions of the sample multiples, and the relative motion (since discovery) and its direction - angle gamma with its error. Positions are taken for the first epoch mostly from Washington Double Star catalogue (WDS, Cat. <I/237>) and from Hipparcos (Cat. <I/239>) or Tycho (Cat. <I/239> and <I/259>) catalogues for the second epoch. Orbital motion in inner subsystems of multiple stars is taken into account in gamma when significant. Table 2 gives the cross-identification of objects and components in different catalogues.
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