Exotic Baryons in Hot Neutron Stars

Abstract

We study the nuclear isentropic equation of state for a stellar matter composed of nucleons, hyperons, and/or ∆-resonances. We investigate different snapshots of the evolution of a neutron star, from its birth as a lepton-rich protoneutron star in the aftermath of a supernova explosion to a lepton-poor regime when the star starts cooling to a catalyzed configuration. We use a relativistic model within the mean-field approximation to describe the hot stellar matter and adopt a densitydependent couplings adjusted by the DDME2 parameterization. We use baryon-meson couplings for the spin-1/2 baryonic octet and spin-3/2 decpuplet determined in a unified manner relying on SU(6) and SU(3) symmetry arguments. We observe that ∆ − is the dominant exotic particle in the star at different entropies for both neutrino-free and neutrino-trapped stellar matter. Also, the presence of ∆-resonances inside the star increases the temperature profile in the star beyond the temperature generated by only nucleons and leptons, contrary to the hyperons (Λ, Σ 0,± , and Ξ 0,− ) that decrease the temperature at intermediate to high densities.

Radial Oscillations in Neutron Stars with Delta Baryons

“…Hence, the couplings can be fixed to reproduce the potentials U Λ = −28 MeV, U Σ = 30 MeV, U Ξ = −4 MeV and U ∆ ≈ −98 MeV in terms of a single free parameter α V . Our choice of α V = 1.0 for the baryon-meson coupling scheme corresponds to an unbroken SU(6) symmetry, and the values of χ ib are shown in Table II taking into account the isospin projections in the lagrangian terms [57].…”