Lithium in the lower red giant branch of 5 Galactic globular clusters
  Lithium is one of the few elements produced during the Big Bang
Nucleosynthesis in the early universe. Moreover, its fragility makes it useful
as a proxy for stellar environmental conditions. As such, the lithium abundance
in old systems is at the core of different astrophysical problems. Stars in the
lower red giant branch allow studying 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 use GIRAFFE spectra to measure the
lithium and sodium abundances of lower red giant branch stars in 5 globular
clusters. These cover an extensive range in metallicity, from [Fe/H]$\sim-0.7$
to [Fe/H]$\sim-2.3$ dex. We find that the lithium abundance in these lower red
giant branch stars forms a plateau, with values from
$\mathrm{A(Li)_{NLTE}}=0.84$ to $1.03$ dex, showing no clear correlation with
metallicity. When using stellar evolutionary models to calculate the primordial
abundance of these clusters, we recover values $\mathrm{A(Li)_{NLTE}}=2.1-2.3$
dex, consistent with the constant value observed in warm metal-poor halo stars,
the Spite plateau. Additionally, we find no difference in the lithium abundance
of first and second population stars in each cluster. We also report the
discovery of a Li-rich giant in the cluster NGC3201, with
$\mathrm{A(Li)_{NLTE}}=1.63\pm0.18$ dex, where the enrichment mechanism is
probably pollution from external sources.
