Overshooting in Massive Stars: Conceptual Problems and Suggested Solution

Abstract

Overshooting (OV) in massive stars faces a basic difficulty: what theoretical models offer is not what stellar structure studies need. The former use ▽=0 and define the OV where the negative convective flux J vanishes, while the latter need to know where the concentration flux Jc vanishes. We suggest that J may be dynamically irrelevant and derive the new dynamic equations for Jc. A new feature emerges: for large concentration gradients ▽C, Jc is no longer proportional to ▽C, as always assumed.