2001ApJ...559..909T

In this paper we study the evolution of ⁷Li in the Galaxy considering the contributions of various stellar sources: Type II supernovae, novae, red giant stars, and asymptotic giant branch (AGB) stars. We present new results for the production of ⁷Li in AGB stars via the hot bottom burning process, based on stellar evolutionary models. In the light of recent observations of dense circumstellar shells around evolved stars in the Galaxy and in the Magellanic Clouds, we also consider the impact of a very high mass-loss rate episode (superwind) before the evolution off the AGB phase on the ⁷Li enrichment in the interstellar medium. We compare the Galactic evolution of ⁷Li obtained with these new ⁷Li yields (complemented with a critical reanalysis of the role of supernovae, novae and giant stars) with a selected compilation of spectroscopic observations including halo and disk field stars as well as young stellar clusters. We conclude that even allowing for the large uncertainties in the theoretical calculation of mass-loss rates at the end of the AGB phase, the superwind phase has a significant effect on the ⁷Li enrichment of the Galaxy.