Rapidly spinning massive pulsars as an indicator of quark deconfinement

We study rotating hybrid stars, with particular emphasis on the effect of spin on the deconfinement phase transition and star properties. Our analysis is based on a hybrid equation of state with a phase transition from hadronic matter containing hyperons to color-superconducting quark matter, where the quark phase is modeled within a relativistic density functional approach. By varying the strength of the vector repulsion and diquark pairing couplings in the microscopic quark Lagrangian, we construct a set of hybrid star sequences with different quark-matter onset densities. This framework ensures consistency with astrophysical and gravitational wave constraints on mass, radius, and tidal deformability. We show how increasing the rotational frequency affects the maximum gravitational mass, oblateness, central energy density of compact stars, as well as the onset of quasiradial oscillations and nonaxisymmetric instabilities. Our results indicate that, for the most favorable parameter sets with strong vector coupling, hybrid stars containing a color-superconducting quark-matter core can account for the fastest-spinning and most massive known neutron star, PSR J0952-0607. In contrast, this pulsar cannot be explained by the purely hadronic equation of state considered in this study. These findings are highly relevant for future observations with the Square Kilometre Array (SKA), which will significantly expand the known pulsar population and enable precise measurements of masses and spin frequencies.