Thermal twin stars within a hybrid equation of state based on a nonlocal chiral quark model compatible with modern astrophysical observations

Abstract

We investigate the extension to finite temperatures and neutrino chemical potentials of a recentlydeveloped nonlocal chiral quark model approach to the equation of state of neutron star matter.We consider two light quark flavors and current-current interactions in the scalar-pseudoscalar,vector, and diquark pairing channels, where the nonlocality of the currents is taken into accountby a Gaussian form factor that depends on the spatial components of the 4-momentum. Withinthis framework, we analyze order parameters, critical temperatures, phase diagrams, equation ofstate, and mass-radius relations for different temperatures and neutrino chemical potentials. Forparameters of the model that are constrained by recent multi-messenger observations of neutronstars, we find that the mass-radius diagram for isothermal hybrid star sequences exhibits the thermaltwin phenomenon for temperatures above 30 MeV.