The Enigma of Li-Rich Giants and its Relation with RV and Stellar Activity Variations

Much of what makes a star lithium rich is still a mystery. Magnetic activity, in particular the phenomena usually associated with it, and the lithium abundance of stars are in general thought to be connected. However as of today, it is unclear just how. In this work, in hopes of shedding light on this conundrum, we study a sample of young but evolved intermediate mass red giants, some of which are lithium rich, in open clusters where planets have been searched. We make use of radial velocity and stellar activity signals to look for relations between the variations observed and the surface lithium abundance of these stars. We find that the measurements of dispersion of the stellar activity signals increase exponentially with the lithium abundance of the stars in our sample. To strengthen our analysis we also look for correlations as well as periodic temporal variations in stellar activity signals that may connect variability observed in radial velocity to stellar activity. High correlations also tend to be found preferentially for stars with higher lithium abundances. Interestingly, we also find that most of the lithium rich giants in our sample either show strong correlations between radial velocity measurements and at least one of the stellar activity indicators considered or reveal periodic variability in these signals. This work thus provides evidence that red giants with higher lithium abundances are also more magnetically active.