The evolution of helium white dwarfs: III. On the ages of millisecond pulsar systems

Abstract

We employed recently computed evolutionary white-dwarf models with helium cores, supplemented by heavier models with carbon-oxygen cores, in order to investigate the ages of millisecond pulsar systems based on the cooling properties of the compact companions. Contrary to the behaviour of more massive white dwarfs, the evolutionary speed of low-mass white-dwarf models is substantially slowed down by ongoing hydrogen burning. By comparing the cooling ages of these models with the spin-down ages of the pulsars for those systems for which reasonable information about the compact companions is available, we found good correspondence between both ages. Based on these models any revisions concerning the temporal evolution of millisecond pulsars do not appear to be necessary.