IUE observations of the symbiotic star CH Cygni during an active phase

Abstract

THE spectrum of CH Cygni usually has the appearance of a normal M6 III star, but at intervals of several years, it has outbursts during which it shows the characteristics of a symbiotic star, that is a blue continuum extending shortward of the B almer discontinuity, and emission lines of He I, Fe II, [Fe II], [S II], [O III]; the Balmer lines and the H and K lines of Ca II present emission wings. The observations of CH Cygni reported here were made to determine whether a symbiotic star is a binary system composed of an M6 giant and a hot subdwarf, or whether it is a cool star surrounded by a thick corona.