Astrometric Study of Two Multiple Stars: ADS 2668 and ADS 8236

Abstract

Based on CCD observations with the Pulkovo 26-inch refractor in 2003–2018, we have obtained the orbit of the visual double star ADS 2668 AB (P = 947 yr, a = 2.9″, e = 0.41, ω = 246°, Ω = 131°, i = 114°, T = 1456 yr) for the first time by the apparent motion parameter (AMP) method, which is consistent with the inner orbit of ADS 2668 Aa-Ab, and improved the orbit of ADS 8236 AB (P = 1996 yr, a = 4.69″, e = 0.39, ω = 201°, Ω = 166°, i = 110°, T = 1246 yr). The inner orbit of the photocenter of ADS 8236 with a period of 4.627 yr has been calculated from the residuals. This orbit of ADS 8236 Ba–Bb supplements the spectroscopic orbit by the elements specifying the orbital plane (i and Ω). In both cases, the planes of the inner and outer orbits are noncoplanar. The presence of an additional companion in the system ADS 2668 is discussed.