ON NONLINEAR RADIAL OSCILLATIONS IN CONVECTIVE RR LYRAE STARS .2. COMPARISON OF A RADIATIVE AND A CONVECTIVE MODEL

An adaptive-grid algorithm is employed to obtain full-amplitude oscillations of a radiative and a convective RR Lyrae model that sits near the red edge. It is shown that this numerical technique is superior to the traditional one in that it is capable of computing smooth radial velocity and light curves. This success is achieved because the adaptive grid is able to detect the ionization zones and to track them during the pulsation cycles. A phenomenological model for turbulent-convective energy transport is employed. The pulsations of the RR Lyrae are computed for the radiative and the convective case. The convective and the radiative simulations are discussed for both the hydrostatic and the full-amplitude models. It is demonstrated that the phenomenon of convective overshooting leads to a secondary maximum on the branch of rising light right after the instant of minimum radius. This feature is shown to be a true signature of the hydrogen convection zone.