Hybrid star structure with the Field Correlator Method

We explore the relevance of the color-flavor locking phase in the equation of state (EoS) built with the Field Correlator Method (FCM) for the description of the quark matter core of hybrid stars. For the hadronic phase, we use the microscopic Brueckner-Hartree-Fock (BHF) many-body theory, and its relativistic counterpart, i.e. the Dirac-Brueckner (DBHF). We find that the main features of the phase transition are directly related to the values of the quark-antiquark potential $V_1$, the gluon condensate $G_2$ and the color-flavor superconducting gap $\Delta$. We confirm that the mapping between the FCM and the CSS (constant speed of sound) parameterization holds true even in the case of paired quark matter. The inclusion of hyperons in the hadronic phase and its effect on the mass-radius relation of hybrid stars is also investigated.Comment: 15 pages, 8 figures ; revised version to be published in the EPJA Topical Issue on "Exotic Matter in Neutron Stars

Strange hadronic stellar matter within the Brueckner-Bethe-Goldstone theory

In the framework of the non-relativistic Brueckner-Bethe-Goldstone theory, we derive a microscopic equation of state for asymmetric and $\beta$-stable matter containing $\Sigma^-$ and $\Lambda$ hyperons. We mainly study the effects of three-body forces (TBFs) among nucleons on the hyperon formation and the equation of state (EoS). We find that, when TBFs are included, the stellar core is almost equally populated by nucleons and hyperons. The resulting EoS, which turns out to be extremely soft, has been used in order to calculate the static structure of neutron stars. We obtain a value of the maximum mass of 1.26 solar masses (1 solar mass $M_o \simeq 1.99 \cdot 10^{33} g$). Stellar rotations increase this value by about 12%.Comment: 4 pages, Latex, 2 figures included. To appear in the Proceedings of '' Bologna 2000 - Structure of the Nucleus at the Dawn of the Century'', May 29- June 3, 2000, Bologna, Ital