Evolution of a stellar polytropic envelope with entropy per baryon S = 45.0 and an initial Bernoulli parameter ε = 0.01 U/μ (corresponding to an initial mass of ≈10 M_⊙). Top panel: the Bernoulli parameter, ε, in units of U/μ. Bottom panel: the stellar mass, M, in units of M_⊙. Both are presented as a function of time, in units of kiloyears.