Current models of stellar evolution predict that stars more massive than
βΌ6Mββ should have completely depleted all lithium (Li) in their
atmospheres by the time when they reach the He core burning phase. Against
this, a non-negligible number of red giants with masses >6Mββ
presenting strong Li lines have recently been reported. Motivated by this
finding, we have carried out a spectroscopic survey of red supergiants (RSGs)
in the Perseus Arm and a selection of young open clusters in the Magellanic
Clouds to assess the presence of the Li I Ξ»6708 doublet line. Based on
a sample of >70 objects, close to one third of RSGs in the Perseus Arm display
noticeable Li lines, with perhaps a trend towards a lower fraction among more
luminous stars. The samples in the Magellanic Clouds are not as large, but hint
at a metallicity dependence. Twenty one RSGs in 5 LMC clusters show a very high
fraction of Li detection, around 40%. Conversely, 17 RSGs in 5 SMC clusters
give only one secure detection. The interpretation of these observational
results is not straightforward, but a mechanism for Li production seems most
likely. Further characterisation work is ongoing, while theoretical studies
into this matter are urgently needed.Comment: Accepted in proceedings for IAU Symposium 361: Massive Stars Near and
Far, held in Ballyconnell, Ireland, 9-13 May 2022. N. St-Louis, J. S. Vink &
J. Mackey, ed