Properties of Symbiotic Stars from Studies in the Optical Region
The traditional definition of Symbiotic Stars (SS) is that of objects which display a combination spectrum (e.g.Merrill, 1950) that is emission lines requiring high-excitation conditions, superposed to the continuum and absorption features of a low-temperature star, most commonly an M-type giant. About one hundred of SS are known and listed today. It is any way apparent that the classification criteria are rather rough, and since the excitation varies from the simple Me to SS with coronal emission, it is not well defined where a clear division should be made. As a re sult, the available lists include a very heterogeneous set of objects, probably different phases in stellar evolution. Moreover it has been remarked that SS show a rather confusing variety in their spectroscopic and photometric behaviour. Different intensities of both absorption and emission lines are reported from star to star. These facts indicate a high degree of individuality among SS, which is partly cause and/or effect of the adopted definitions.
KeywordsMonthly Notice Radial Velocity Curve Cool Component Symbiotic Star Nova Outburst
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