Spectroscopy of the shell episode of η Car (1981-1983).

Abstract

High-dispersion spectra of η Car obtained in March 1974, Dec. 1981, and Feb. 1983 have been compared. The spectrum of Dec. 1981 shows conspicuous deviations from the usual spectral appearance of η Car; all lines originating from high ionization and/or excitation levels have dramatically faded. The P Cygni characteristics of the Balmer lines are more pronounced in the spectra of 1981 and 1983. The spectroscopic variations are explained as a result of changing ionization/excitation conditions due to an episodic ejection of a dense shell with a maximum velocity of about 600 km/s. The dense shell screens the UV radiation of the hot core supposed to produce the highly ionized and/or excited atoms in the extended envelope aroung η Car.