THE ACTIVITY OF THE F9 GIANT AND PROCESSES IN THE CAPELLA BINARY-SYSTEM

Observations of Capella in the He I 10 830 Angstrom line obtained at t he Crimean Astrophysical Observatory since 1980 are analyzed. These ob servations reveal for the first time asymmetrical profiles of this lin e, and enable identification of a weak broad component belonging to th e active F9 giant. The main absorption in the He I 10 830 Angstrom lin e is formed in the vicinity of the quiescent G6 giant, and varies with the 104-day orbital period. It also displays long-term variability on a timescale of more than five years. The equivalent widths of the bro ad component vary with a period of 8.25 days, which is similar to the rotational period of the F9 giant. Physical models for the manifestati on of activity in the binary system that can explain the complicated b ehavior of the helium line are discussed.