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 that of nuclear matter saturation density po, a neutron star will become a hyperon star. This transition is strongly influenced by the coupling constants of hyperons to mesons and a different parameter set. For a given parameter set, a minimum transition baryon density exists when the hyperon coupling ratios satisfy x(H sigma) = x(H omega) = x(H rho) = 0.65 or x(H sigma) = x(H omega) = 0.62,x(H rho) = 0.7.