Massive neutron stars with quark-hybrid matter core

Using a nonlocal extension of the SU(3) Nambu-Jona Lasinio model, which reproduces several of the key features of Quantum Chromodynamics, we show that mixed phases of deconfined quarks and confined hadrons (quark-hybrid matter) may exist in the cores of neutron stars as massive as around $2.1\, M_\odot$. According to our study, the implications for the recently discovered, massive neutron star PSR J1614--2230, whose gravitational mass is $1.97\pm 0.04\, M_{\odot}$, are that this neutron star may contain an extended region of quark-hybrid matter at it center, but no pure quark matter.