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The Gaia-ESO survey recently reported on a large sample of lithium (Li)abundance determinations for evolved stars in the rich open cluster Trumpler20. They argue for a scenario where virtually all stars experience post mainsequence mixing and Li is preserved in only two objects. We present analternate explanation, where Li is normal in the vast majority of cluster starsand anomalously high in these two cases. We demonstrate that the Li upperlimits in the red giants can be explained with a combination of main sequencedepletion and standard dredge-up, and that they are close to the detectedlevels in other systems of similar age. In our framework, the two detectedgiants are anomalously Li-rich, and we propose that both could have beenproduced by the engulfment of a substellar mass companion of 16(+6-10) M_J.This would imply that ~5% of 1.8 solar mass stars in this system, and byextension elsewhere, should have substellar mass companions of high mass thatcould be engulfed at some point in their lifetimes. We discuss future teststhat could confirm or refute this scenario.

On Lithium-Rich Red Giants. II. Engulfment on the Giant Branch of Trumpler 20