Empirical Constraints on Convective Core Overshoot

Abstract

In stellar evolution calculations, the local pressure scale height is often used to empirically constrain the amount of convective core overshoot. However, this method brings unsatisfactory results for low-mass stars (< 1.1 -1.2 Mo for Z= \Zs) which have very small cores or no convective core at all. Following Roxburgh's integral constraint,we implemented an upper limit of overshoot within the conventional method of alpha parameterization in order to remove an overly large overshoot effect on low-mass stars. The erroneously large effect of core overshoot due to the failure of alpha parameterization can be effectively corrected by limiting the amount of overshoot to < 15 % of the core radius. 15 % of the core radius would be a proper limit of overshoot which can be implemented in a stellar evolution code for intermediate to low mass stars. The temperature structure of the overshoot region does not play a crucial role in stellar evolution since this transition region is very thin.Comment: 15 pages, 5 figures, accepted for A