ORBITAL ELEMENTS OF BETA-LYRAE AFTER THE 1ST 100 YEARS OF INVESTIGATION

A detailed analysis of 1532 new and published radial velocities of the B6-8II component (accumulated over a century of spectroscopic observa tions), and 33 published velocities of the Be component of beta Lyr le d to the following results: (a) A new accurate quadratic ephemeris, ba sed solely on radial velocities, was derived which predicts correctly even the very first photometric minima observed as early as 1784. (b) No convincing evidence of significant deviations of the observed times of minima from the new ephemeris was found; there is a suspicion of p ossible slight gamma-velocity variation which, if confirmed, may be du e to long-term variations in the circumstellar matter within the syste m rather than to the presence of a third star in the system. (c) An at tempt at the very first direct test of the theory of large-scale mass exchange between the binary components has been carried out. Although not conclusive with the data at hand, this result does not contradict the idea that an essentially conservative mass transfer from the B6-8I I star towards the Be component is presently going on in the system; ( d) Values of M1 sin3 i and M2 sin3 i of unprecedented accuracy (probab ly of 1% and 3% for the B6-8II and Be star, respectively) were derived from the combined orbital solutions for only the high-dispersion velo cities. For a plausible range of the orbital inclination (80-90-degree s), this determination leads to a consistent model in which the B6-8II star fills its Roche lobe and corotates with the orbital motion.