The Böhm-Vitense Gap: The Role of Turbulent Convection

Abstract

Bohm-Vitense gaps, discontinuities in the distribution of A-F type stars along the main sequence, have traditionally been attributed to the abrupt onset of strong convection (8000 K ≥ ≥ 6400 K) in stellar atmospheres and envelopes. Using the full spectrum of turbulence model to describe convective transport (Canuto, Goldman, & Mazzitelli) both in the interior and in the atmosphere yields a very sharp transition between structures that are convective only in the surface layers and structures that show a well-developed convection also in the interior. This produces a sudden change in the of stars, around 6800 K. Using numerical simulations, we show that this feature produces a stellar depletion that is consistent with the gap at 0.33 B-V 0.38. The standard mixing-length theory does not show this behavior. Consequently, this particular gap is a Teff gap and not a color gap. In fact, it is also present in the V-I distribution of the Hyades stars.