Generating dynamical black hole solutions

We prove a theorem that characterizes a large family of nonstatic solutions to Einstein equations, representing, in general, spherically symmetric Type II fluid. It is shown that the best known dynamical black hole solutions to Einstein equations are particular cases from this family. Thus we extend a recent work of Salgado [12] to nonstatic case. The spherically symmetric static black hole solutions, for Type I fluid, are also retrieved.