IS THERE A POPULATION-II ANALOGY TO THE F-STAR LITHIUM DIP

Observers have found a small number of lithium-depleted halo stars in the temperature range of the Spite plateau, The current status of the mass-loss hypothesis for producing the observed lithium dip in Populat ion (Pop) I stars is briefly discussed and extended to Pop II stars as a possible explanation for these halo objects, Based on detections of F-type main-sequence variables, mass loss is assumed to occur in a na rrow temperature region corresponding to this ''instability strip.'' A s Pop II main-sequence stars evolve to the blue, they enter this narro w temperature region, then move back through the lower temperature are a of the Spite plateau, If 0.05 M. (solar mass) or more have been lost , they will show lithium depletion, This hypothesis affects the lithiu m-to-beryllium abundance, the ratio of high- to low-lithium stars, and the luminosity function, Constraints on the mass-loss hypothesis due to these effects are discussed, Finally, mass loss in this temperature range would operate in stars near the turnoff of metal-poor globular clusters, resulting in apparent ages 2 to 3 Gyr (gigayears) older than they actually are.