THERMAL WAVES AND UNSTABLE CONVECTION IN ZZ CETI STARS

Abstract

We analyze the stability criteria by convection in ZZ Ceti stars when the thermal relaxation times are not negligible. Using the Cattaneo law and the Mixing Length Theory in the degenerate regimen, is shown that the heat can be propagated by thermal waves and predicts quasi periodic pulses in luminosity. This formalism is consistent with the semianalytically approaches to temperature variations and several ZZ Ceti light curves.