Chromospherically active stars

We found that iota Gem and HD 179094 have carbon isotope ratios already affected by extra-mixing, even though being in the evolutionary stage below the red giant branch luminosity bump. About half of the low-mass giants, for which the lithium abundance was determined, follow the first dredge-up predictions; however, other stars have Li abundances reduced as predicted by the thermohaline-induced mixing. The intermediate-mass stars have Li abundances reduced as predicted by the rotation-induced mixing.

We found that in low-mass chromospherically active RS CVn stars extra mixing of lithium along with carbon isotopes may begin earlier than in normal giants. The Li-rich RS CVn giant V* OP And has quite large C/N and carbon isotope ratios, and raises questions about the origin of its lithium enhancement.