Title: Evolutionary sequences for hydrogen-deficient white dwarfs,
Abstract: We present a set of full evolutionary sequences for white dwarfs with
hydrogen-deficient atmospheres. We take into account the evolutionary history
of the progenitor stars, all the relevant energy sources involved in the
cooling, element diffusion in the very outer layers, and outer boundary
conditions provided by new and detailed non-gray white dwarf model atmospheres
for pure helium composition. These model atmospheres are based on the most
up-to-date physical inputs. Our calculations extend down to very low effective
temperatures, of $\sim 2\,500$~K, provide a homogeneous set of evolutionary
cooling tracks that are appropriate for mass and age determinations of old
hydrogen-deficient white dwarfs, and represent a clear improvement over
previous efforts, which were computed using gray atmospheres.