On the maximum rotational frequency of neutron and hybrid stars

We construct self-consistent equilibrium sequences of general relativistic, rotating neutron star models. Special emphasis in put on the determination of the maximum rotation frequency of such objects. Recently proposed models for the equation of state of neutron star matter are employed, which are derived by describing the hadronic phase within the many-body Brueckner-Bethe-Goldstone formalism, and the quark matter phase within the MIT bag model using a density dependent bag constant. We find that the rotational frequencies of neutron stars with deconfined quark phases in their cores rival those of absolutely stable, self-bound strange quark matter stars. This finding is of central importance for the interpretation of extremely rapidly rotating pulsars, which are the targets of present pulsar surveys.