Hybrid stars with a quark phase described by the Nambu-Jona-Lasinio model are studied. The hadron-quark model used to determine the stellar matter equation of state favors the appearance of quark matter: the coincidence of the deconfinement and chiral transitions and a low vacuum constituent quark mass. These two properties are essential to build equations of state that predict pure quark matter in the center of neutron stars. The effect of vector-isoscalar and vector-isovector terms is discussed, and it is shown that the vector-isoscalar terms are necessary to describe $2M_{\odot }$ hybrid stars, and the vector-isovector terms result in larger quark cores and a smaller deconfinement density.

• Received 6 July 2016

DOI:https://doi.org/10.1103/PhysRevD.94.094001