1302.5707 (Joel D. Tanner et al.)

Variation of Stellar Envelope Convection and Overshoot with Metallicity    [PDF]

Joel D. Tanner, Sarbani Basu, Pierre Demarque

We examine how metallicity affects convection and overshoot in the superadiabatic layer of main sequence stars. We present results from a grid of 3D radiation hydrodynamic simulations with four metallicities ($Z=0.040$, 0.020, 0.010, 0.001), and spanning a range in effective temperature ($4950 < \rm T_{\rm eff} < 6230$). We show that changing the metallicity alters properties of the convective gas dynamics, and the structure of the superadiabatic layer and atmosphere. Our grid of simulations show that the amount of superadiabaticity, which tracks the transition from efficient to inefficient convection, \rev{is sensitive to changes in metallicity. We find that increasing the metallicity forces the location of the transition region to lower densities and pressures, and results in larger mean and turbulent velocities throughout the superadiabatic region.} We also quantify the degree of convective overshoot in the atmosphere, and show that it increases with metallicity as well.

View original: http://arxiv.org/abs/1302.5707