Compact Stars within a SU(3) Quark Meson model

Andreas Zacchi, Goethe Universität

The inner regions of the most massive compact stellar objects might be occupied by a phase of quarks.  We discuss stable hybrid stars, i.e. compact objects with an outer layer composed of nuclear matter and with a core consisting of quark matter. For the outer nuclear layer we utilise a density dependent nuclear equation of state and we use a chiral SU(3) Quark-Meson model with a vacuum energy pressure to describe the objects core. The appearance of a disconnected mass-radius branch emerging from the hybrid star branch implies the existence of a third family of compact stars, so called twin stars. Twin stars did not emerge as the transition pressure has to be relatively small with a large jump in energy density. The quark matter equation of state however exhibits the onset of the chiral phase transition and for a certain parameter choice, new solutions appear as two stable branches in the mass-radius relation, i.e. twin stars. We find solutions which are compatible with causality, the stability conditions of dense matter, the astrophysical constraints of the rotation of the millisecond pulsar PSR J1748-2446ad and the two solar mass constraint.