Magnetic mixing and the Arcturus problem

Abstract

A model for main-sequence mixing driven by the buoyancy of magnetic flux tubes is proposed, and the effect of such a process on the CNO isotopes is investigated. Such a mixing scheme applied to a 2.0 solar mass model is used to predict the ratios N-14/N-15, O-16/O-17, O-16/O-18, and C/O for any observed combination of C-12/C-13 and C/N. Unlike meriodinal mixing, the penetration depth of magnetic mixing depends critically on the early history of the star. Therefore, for a given C-13 enhancement, the N-14 enhancement may vary making magnetic mixing a viable model both for stars with moderate C-13 and N-14 enhancement such as Beta Gem and for stars with a large C-13 enhancement and a low N-14 enhancement such as Alpha Boo.