On the origin of Lithium

Paolo Molaro (Astronomical Observatory of Trieste)

Abstract: Li is the element with the largest number of astrophysical nucleosynthetic processes. Although a primordial element, it is also produced by spallation processes in the interstellar medium, in a slow process lasting billions of years. The Li abundance in the old halo population of the Galaxy, however, is lower by a factor 3 than predicted by Big Bang models. This well known issue is known as the Cosmological Lithium problem. In this talk, I will present a tentative stellar fix to the problem, dealing with pre-main sequence depletion.
One or more Galactic sources of Li are still to be identified in order to reach the Li abundance observed in the pre-solar nebula. Only recently, after decades of unsuccessful Li search, its parent nuclei Be-7 has been detected in novae outburst. Observations of Be-7 in few recent novae will be presented. The  Li yields obtained from novae overproduce the meteoritic Li abundance by several orders of magnitude, and are therefore candidates for “the” source of Galactic lithium. Within this framework,  the different Li evolution of the disk stars could be explained. The Li abundance in some Gaia – Enceladus candidate stars will be also presented and discussed.