Aguilera-Gómez, C., Monaco, L., Mucciarelli, A., Salaris, M., Villanova, S., Pancino, E.
2022, A&A, 657, 33
https://ui.adsabs.harvard.edu/abs/2022A%26A…657A..33A/abstract
Lithium (Li) is one of the few elements produced during Big Bang nucleosynthesis in the early universe. The discrepancy between cosmological estimation of the Li produced in the Big Bang Nucleosynthesis and measurements in old stars is known as the cosmological lithium problem. Explanations for this difference either rely on new physics and modifications to current reaction rates or in that the measured abundance for old stars is not primordial.
Stars on the lower red giant branch are key to studies of globular clusters where main sequence stars are too faint to be observed. We use these stars to analyze the initial Li content of the clusters and compare it to cosmological predictions, to measure spreads in Li between different stellar populations, and to study signs of extra depletion in these giants.
We find that the lithium abundance in these lower red giant branch stars forms a plateau showing no clear correlation with metallicity. When using stellar evolutionary models to calculate the primordial abundance of these clusters, we recover values of consistent with the constant value observed in warm metal-poor halo stars. We also report the discovery of a Li-rich giant in the cluster NGC 3201.