Nonlinear investigation of the pulsational properties of RR Lyrae variables

Abstract. We present a theoretical investigation on pe-riods and amplitudes of RR Lyrae pulsators by adopting stellar parameters which cover the range of theoretical evolutionary expectations. Extensive grids of nonlinear, nonlocal and time-dependent convective RR Lyrae enve-lope models have been computed to investigate the pul-sational behavior in both fundamental and rst overtone modes at selected luminosity levels and over an eective temperature range which covers the whole instability re-gion. In order to avoid spurious evaluations of modal sta-bility and pulsation amplitudes, the coupling between pul-sation and convection was followed through a direct time integration of the leading equations until radial motions approached their limiting amplitude. Blue and red bound-aries for pulsational instability into the HR diagram ar