Third family of superdense stars in the presence of antikaon condensates -art. no. 055805

The formation of K- and (K) over bar (o) condensation in beta -equilibrated hyperonic matter is investigated within a relativistic mean field model. I n this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. It is found that antikaon condensation is not o nly sensitive to the equation of state but also to the antikaon optical pot ential depth. For large values of the antikaon optical potential depth, K- condensation sets in before the appearance of negatively charged hyperons. We treat K- condensation as a first-order phase transition. The Gibbs crite ria and global charge conservation laws are used to describe the mixed phas e, Nucleons and A hyperons behave dynamically in the mixed phase. A second- order phase transition to Ro condensation occurs in the pure K- condensed p hase. Along with K- condensation, K- condensation makes the equation of sta te softer, thus resulting in smaller maximum mass stars compared with the c ase without any condensate. This equation of state also leads to a stable s equence of compact stars called the third family branch, beyond the neutron star branch. The compact stars in the third family branch have different c ompositions and smaller radii than that of the neutron star branch.