How and When Will a Neutron Star Become a Hyperon Star?

In the framework of the extended relativistic mean-field theory with hyperons, the properties of neutron star matter have been investigated. It is found that at a density of four to five times of nuclear matter saturation density ρ₀, a neutron star will become a hyperon star. This transition is strongly influenced by the coupling constants of hyperons to the mesons and different parameter set. For a given parameter set, a minimum transition baryon density exists when the hyperon coupling ratios satisfy x_Hσ = x_Hω = x_Hρ = 0.65 or x_Hσ = x_Hω = 0.62, x_Hρ = 0.7.