Lithium rich red giant branch stars

Abstract

Lithium rich K giant stars are found at the luminosity bump of the first ascending red giant branch. The discovery of these stars has given a recent impulse to advances in the theory of stellar evolution. Important connections appeared between thermonuclear processes, rapid mixing, surface activity, rotation and mass loss episodes. How could such lithium surface enrichment be produced? Two concurring scenarios offer completely different explanations: an internal stellar origin and an external one in which planets are engulfed. We will discuss the present state of these matters. © 2006 Springer-Verlag Berlin Heidelberg.