[vsnet-chat 389] re question for symbiotic star

[iijima@astras.pd.astro.it]

						17 June 1997, Asiago

 The "Symbiotic Stars" is a phenomenal definition. They show spectra of 
red type stars (type of K, M, Mira, C) superimposed by emission lines of 
highly ionized ions, e.g. HeI, He II, [O III], Fe II, [Fe VII], etc. 
"Symbiotic" does not have the biological meaning in this case, but means 
co-existent, namely co-exist cool and hot properties. Classical Mira 
variables show emission lines of H I, Fe I, etc., but they are not symbiotic 
stars.
 Symbiotic stars must not be binary systems. Even nowadays some astronomers 
still insist their single star models, e.g. a red type giant with very 
strong stellar corona, or a planetary nebula now is born from a red giant. 
But today we know that most (I want to say "all") of the symbiotic stars 
are binary systems consisting of a red giant and a hot component, the 
latter could be a main-sequence star, white dwarf, sub-dwarf etc. The hot 
component should be hot enough to excite the emission lines of the highly 
ionized ions, but their own properties are not important for the definition 
of the symbiotic stars. The high temperature of the hot component is 
usually due to mass accretion from the red component.
						Dr. Takashi IIJIMA

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