Emission Line Ratio Classification of Symbiotic Stars

Abstract

A 2-dimensional classification system for symbiotic stars based on the 5007/4861 and 3727/5007 line ratios adapted from the method of Baldwin et al.(1981) is presented. It is shown that a simple measurement suffices to classify stars and no reddening has to be taken into account. Symbiotics fall into 2 distinct classes in the line ratio plot. The dusty and S types. Neither type coincides with either the planetary nebulae or the HII region locus. The highest excitation is found for the dusty types. The two dimensional distribution can be interpreted as evolutionary, the more evolved Mira containing symbiotics lying closer to the PN locus. The fact that there are few D, D’ type symbiotics would indicate that the phase between Mira and PN is short.