Orbits of Hyades multiple-lined spectroscopic binaries - Paper 3: The triple-lined system HD 29608

The results of a new spectroscopic investigation of the Hyades triple system HD 29608 are presented. High-resolution observations of the system, which is composed of a spectroscopic binary and a close visual companion (separation 0".44), made at McDonald Observatory, reveal the spectra of all three stars, show that the secondary of the spectroscopic binary and the third star are of very similar brightness, and provide the first radial velocities for these two stars. The radial velocities of the primary and secondary of the spectroscopic binary allow the determination of the spectroscopic binary orbit, results include minimum masses, m(Aa)sin(3) i = 0.699 +/- 0.010 M-. and m(Ab) sin(3) i = 0.570 +/- 0.006 M-., which are slightly less than the actual masses, and a linear separation a sin I = (134.5 +/- 0.7) x 10(6) kin between Aa and Ab. The corresponding angular separation on the sky is 18.1 mas. The analysis also reveals a slow steady increase of the radial velocity of the center of mass of the spectroscopic binary caused by orbital motion in the visual binary orbit, which is of long, but unknown, period. The radial velocities of the third star show a corresponding slow steady decrease. These two long-term radial-velocity changes fix the radial velocity of the centre of mass of the entire system: Gamma = 40.66 +/- 0.79 km s(-1).