Properties of semi-convection and convective overshooting for massive stars

Abstract

Properties of semi-convection and core convective overshooting of stars with 15 $M_{\odot}$ and 30 $M_{\odot}$ are calculated in the present paper. New methods are used to deal with semi-convection. Different entropy gradient is used when adopting the Schwarzschild method and the Ledoux method which are used to confine the convective boundary and to calculate the turbulent quantities: $\frac{\partial \overline{s}}{\partial r}=-\frac{c_{p}}{H_P}(\nabla-\nabla_{\rm ad})$ when the Schwarzschild method is adopted and $\frac{\partial \overline{s}}{\partial r}=-\frac{c_{p}}{H_P}(\nabla-\nabla_{\rm ad}-\nabla_{\mu})$ when the Ledoux method is adopted. Core convective overshooting and semi-convection are treated as a whole part and the development of them are found to present nearly opposite tendency, more intensive core convective overshooting lead to weaker semi-convection. The influences of different parameters and the convection processing methods on the turbulent quantities are analyzed in this paper. Increasing the mixing-length parameter $\alpha$ leads to more turbulent dynamic energy in the convective core and prolonging the overshooting distance but depressing the development of semi-convection. The Ledoux method adopted leads to overshooting extending further and semi-convection developing suppressed.