2021ApJ...907L..37D

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^+0.08M_☉) 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 M_TOV (M_max) is either determined by the secular instability or a phase-transition induced collapse. We find the largest values for M_max/M_TOV in cases where the phase transition determines M_max, which shifts our fit result to M_{max}/M_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.