EVIDENCE FOR ACTIVITY OF CAPELLA

Results of observations of Capella in the infrared He I lambda 10830 A ngstrom line obtained with the Shajn 2.6 m telescope of the Crimean As trophysical Observatory over 10 years are analyzed. The He I equivalen t width varies with the 104-day orbital period, and the amplitude of t hese variations in September 1993-March 1994 was significantly lower t han during our observations in 1985-1988. A comparison of these observ ations with those obtained by us since 1985 suggests the presence of a n activity cycle with a period of at least 5 years. The main He I abso rption forms in the chromosphere of the quiescent G6 giant, but near t he maximum of the activity cycle, helium absorption forming on the mor e active, hotter F9 giant becomes observable. These helium data, toget her with the EUV results for the high-temperature Fe XX-Fe XXIII lines can de explained using a model in which an enhanced magnetized stella r wind originating from the hot corona on the active F9 giant reaches the Lagrangian point and then forms a shock wave in the corona of the quiescent G6 giant.