Self-similar expansion of white dwarfs

Properties of plasma expansion that propagates in an electron-positron-ion dense plasma are investigated. Suitable hydrodynamic equations for the ions and ultrarelativistic degenerate electrons and positrons are used. Using self-similar transformation, the basic set of nonlinear equations is solved numerically. Typical values of white dwarf stars are used to estimate the behavior of the ion number density and ion fluid velocity. The positive ions are found to initially slowly escape with high velocity when the ion-to-electron density ratio increases. For higher values of the electron number density, the self-similar solution validity domain decreases. The relevance of the results to white dwarf expansion and collapse is highlight.