An astrometric study of the triple star ADS 48

We analyze the series of relative positions of the hierarchical triple syst em ADS 48 ABF (AB = 6", AF = 327") obtained with the 26-inch Pulkovo refrac tor during 1961-1995 and measured with the Fantazia automated measuring sys tem. A new relative orbit of pair AB is determined by the method of apparen t-motion parameters using new observations and all the available astrometri c and astrophysical data on this star, including its Hipparcos parallax. Th e new orbit for pair AB is reliably reconciled with all the new and previou s observations of this star for the sum of the components' masses equal to 1.4M(circle dot). The Pulkovo observations (1961-1995) revealed a perturbat ion with a period of 15 years and an amplitude rho similar to 0." 01, sugge sting the presence of an unseen companion with a mass as large as 0.05M(cir cle dot). Since the oscillation amplitude is at a noise level, the orbit of the suspected companion cannot be determined. Assuming that stars A and B have the same mass, which corresponds to astrophysical data, we computed th e parameters of apparent motion of component F relative to the center of ma ss of system AB and determined the family of orbits that satisfied the Pulk ovo observations. All the computed orbits are steeply (more than 55 degrees ) inclined to the orbital plane of AB. The orbital motion of star F has bee n investigated for the first time. (C) 2001 MAIK "'Nauka/Interperiodica".