We examine the role of hyperons in a neutron star based on the relativisticmean field approach. For nuclear matter below 1.5 times the normal nucleardensity we constrain the model parameters by using the symmetric nuclear matterproperties and theoretical investigations for neutron matter in the literature.We then extend the model to higher densities by including hyperons andisoscalar vector mesons that contain strangeness degree of freedom. We confirmthat the $\phi$ meson induces a $\Lambda$ repulsive force and hardens theequation of state. The hardening arising from the $\phi$ meson compensates thesoftening from the existence of hyperons. The flavor SU(3) and spin-flavorSU(6) relations are examined as well. We found that the coupling constantsfitted by neutron matter properties could yield high enough maximum mass of aneutron star and the obtained results satisfy both the mass and radiusconstraints. The onset of the hyperon direct Urca process in neutron stars isalso investigated using our parametrization.
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