Multimodal radial pulsational instability in a prenova model

A prenova model, consisting of a white dwarf unstably burning a shell of accreted hydrogen, was tested for stability against radial pulsations. The pulsational analysis included terms due to thermal imbalance. The model was found to be pulsationally unstable in all of the modes examined, save one in which the thermal-imbalance integrals made the crucial damping contribution. An evaluation of some in the present analysis is followed by a more general discussion in which it is concluded that multimodal radial pulsational instability can occur in a wide variety of thermally unstable, shell-burning stars. A brief discussion of some consequences of such instability, including its possible connection with the rapid blue variables, concludes the article. Subject headings: instabilities - novae - pulsation - white dwarf stars