Motions in wide pairs at various galactocentric distances

Abstract

The motions of the components of wide binary stars in the regular Galactic gravitational field on time scales ~10¹⁰ yr at various Galactocentric distances R₀ have been studied numerically. Near the Galactic center, the influence of the bar has been taken into account. The regions of restricted motions of the components in wide pairs have been found depending on the initial conditions: the magnitude of the relative velocity of the components, their mutual distance, and the inclination of the relative velocity vector to the Galactic plane. The shape and sizes of these regions are shown to depend significantly on R₀: the sizes of the region of initial conditions corresponding to restricted motions increase with R₀. Profound changes in the eccentricity of the binary orbit occur at inclinations close to 90◦, which can lead to close approaches of the stars with a pericenter distance less than 1 AU. For retrograde motions (the binary rotates in a direction opposite to the Galactic rotation), there are elongated branches of the region of restricted motions in all cases, which extend at least to 10 pc in some cases.