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High-resolution spectroscopy is presented for five luminous (Mbol_ ~ -6 to -7) asymptotic giant branch (AGB) stars in the Small Magellanic Cloud (SMC). These stars are found to be metal-poor (Fe/H ~ -0. 5) but s-process-enriched, relative to Fe-peak elements, by up to a factor of 10: these are s-process enhancements that are comparable to those observed in Galactic S stars; thus, these SMC AGB stars have experienced a third dredge-up. Of more interest is the fact that all five red giants have rather strong Li I resonance lines (6707 A) ; an abundance analysis reveals these stars to have Li abundances that are 100-1000 times that expected in red giants. We argue that these very luminous (and probably massive) AGB stars have synthesized Li as predicted by certain stellar models of hot-bottom convective-envelope burning. We discuss the observations and models as a basis for understanding certain phases of red giant evolution and as a potentially significant source of Li in the universe.
Smith et al. (Sun,) studied this question.