Abstract
The results of a survey of 279 late-type giants and supergiants for the spectral lines of the radioactive element technetium (Tc I) at 4297, 4262, and 4238 A are presented. The following conclusions are reached: (1) the presence of Tc correlates very strongly with the existence of light variability; (2) evolutionary MS stars show Tc and spectroscopic MS stars do not show Tc; (3) single S stars show Tc; (4) SC stars show Tc; (5) about 75 percent of the C stars show Tc; and (6) Ba II stars do not show Tc. The findings are compatible with predictions from stellar evolution theory. 78 references.
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