Phase Transition to Hyperon Matter in Neutron Stars
  Recent progress in the understanding of the high density phase of neutron stars advances the view that a substantial fraction of the matter consists of hyperons. The possible impacts of a highly attractive interaction between hyperons on the properties of compact stars are investigated. We find that a hadronic equation of state with hyperons allows for a first order phase transition to hyperonic matter. The corresponding hyperon stars can have rather small radii of R=8 km. 
Jurgen Schaffner-Bielich, Matthias Hanauske, Horst Stocker, and Walter   Greiner