WIYN Open Cluster Study. VI. Interpretive Models of Light‐Element Depletion from M67 Subgiants

Abstract

We present evolutionary models of subgiant stars in M67 that follow the surface abundances of lithium and beryllium. These models include a number of physical processes that have been proposed as explanations for the main-sequence depletion of lithium in the Hyades. We use the observed lithium abundance as a function of temperature in M67 subgiants and the correlation between lithium and beryllium depletion to distinguish between these models. We find that constant main-sequence mass loss and diffusion are strongly ruled out as viable mechanisms for light-element depletion in main-sequence stars. Rotationally induced mixing is strongly supported by the lithium- and beryllium-depletion correlation observed in Population I field F stars; such mixing is also consistent with the lithium abundances observed in M67 subgiants, although we discuss some possible complications.