Nuclear and Particle Physics, Astrophysics and Cosmology, T-2

Symmetry energy, neutron star crust, neutron skin thickness, and the r-mode instability

Isaac Vidana
Univ. of Coimbra

We analyze different aspects of the nuclear symmetry energy by using both microscopic and phenomenoliogical approaches to the nuclear equation of state. Microscopic includes Brueckner-Hatree-Fock, the variational form due to Akmal, Pandharipande, and Ravenhall, and a parametrization of recent Auxiliary Field Diffusion Monte Carlo. For phenomenological approaches we use Skyrme forces and relativistic mean field models. Specifically, we study correlations of symmetry energy parameters, the slope L and the curvature K_symm, with the neutron slin thinkness (in neutron rich isotopes) and the crust-core transition point (in neutron stars). We confirm that there is an inverse correlations between the neutron slin thinkness and the transition density. The role of L in the r-mode instability of neutron stars is also studied. The r-mode instablity region is smaller for models which give larger values of L. Using the measured spin frequency and estimated core temperature of the pulsar in the low mass X-ray binary 4U 1608-52, we show that observational data seem to favor L values larger than ~50 MeV.

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