Far UV variability of theta CrB in 1980-1985. II. Evidence for variability patterns and ionization dependence.

Abstract

Far UV observations of Theta CrB obtained in 1980-1985 with the IUE are presented which provide evidence for long-term variability patterns associating the shape, velocity and strength of the Si IV, Al III, and Fe III lines. A differential variable behavior between lines arising from different ionization levels is also noted. The present results are in contradiction with the findings of Underhill (1985), and it is suggested that her results are biased by the averaging of velocities, which lowered the amplitude of the velocity variations, and by the higher weight given to the period of time when the expansion velocities were constant.