Rapidly Spinning Compact Stars with Deconfinement Phase Transition

We study rapidly spinning compact stars with equations of state featuring a first-order phase transition between strongly coupled nuclear matter and deconfined quark matter by employing the gauge/gravity duality. We consider a family of models that allow purely hadronic uniformly rotating stars with masses up to approximately 2.9 M⊙, and are therefore compatible with the interpretation that the secondary component (${2.59}_{-0.09}^{+0.08}\,{M}_{\odot }$) in GW190814 is a neutron star. These stars have central densities that are several times the nuclear saturation density, so that strong coupling and non-perturbative effects become crucial. We construct models where the maximal mass of static (rotating) stars MTOV (Mmax) is either determined by the secular instability or a phase-transition induced collapse. We find the largest values for Mmax/MTOV in cases where the phase transition determines Mmax, which shifts our fit result to ${M}_{\max }/{M}_{\mathrm{TOV}}={1.227}_{-0.016}^{+0.031}$, a value slightly above the Breu–Rezzolla bound ${1.203}_{-0.022}^{+0.022}$ inferred from models without phase transition.