Properties of semi-convection and convective overshooting for massive stars

Abstract

The properties of semi-convection and core convective overshooting of stars with masses of 15 and 30 M⊙ are calculated in the present article. New methods are used to deal with semi-convection. Different entropy gradients are used when adopting the Schwarzschild and Ledoux methods, which are used to confine the convective boundary and calculate the turbulent quantities: ∂s̄/∂r = -(cp/HP)(∇ - ∇ad) when the Schwarzschild method is adopted and ∂s̄/∂r = -(cp/HP)(∇ - ∇ad - ∇μ) when the Ledoux method is adopted. Core convective overshooting and semi-convection are treated as a whole and their development is found to present almost opposing tendencies: more intensive core convective overshooting leads to weaker semi-convection. The influence of different parameters and convection processing methods on the turbulent quantities is analysed in this article. Increasing the mixing-length parameter α leads to more turbulent dynamic energy in the convective core and prolongs the overshooting distance but depresses the development of semi-convection. Adoption of the Ledoux method leads to overshooting extending further and semi-convection development being suppressed. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.