The lithium dip and Scuti variables: observational evidence, main-sequence mass loss and blue stragglers

Abstract

The implications of observational evidence on the recent suggestion that the lithium dip seen in older galactic clusters is due to substantial main-sequence mass loss from δ Sct stars are analyzed. Examination of evidence for such mass loss in δ Sct stars, the relative locations of the instability strip and the lithium dip, and the implied mass-loss rates for a δ Sct star to evolve down the main sequence to the lithium dip are all inconsistent with these pulsational variables being the progenitors of lithium dips. The lithium abundance determinations in blue stragglers and δ Sct stars are still too few to make definitive statements as to the validity of the mass-loss hypothesis, but at present do not appear to favour this specific scenario