The Lithium Flash - Thermal instabilities generated by lithium burning in RGB stars

We present a scenario to explain the lithium-rich phase which occurs on the red giant branch at the so-called bump in the luminosity function. The high transport coefficients required to enhance the surface lithium abundance are obtained in the framework of rotation-induced mixing thanks to the impulse of the important nuclear energy released in a lithium burning shell. Under certain conditions a lithium flash is triggered off. The enhanced mass loss rate due to the temporary increase of the stellar luminosity naturally accounts for a dust shell formation.