Asymmetric nuclear matter and neutron-skin in extended relativistic mean field model

The density dependence of the symmetry energy, instrumental in understanding the behaviour of the asymmetric nuclear matter, is investigated within the extended relativistic mean field (ERMF) model which includes the contributions from the self and mixed interaction terms for the scalar-isoscalar ($\sigma$), vector-isoscalar ($\omega$) and vector-isovector ($\rho$) mesons upto the quartic order. Each of the 26 different parameterizations of the ERMF model employed are compatible with the bulk properties of the finite nuclei. The behaviour of the symmetry energy for several parameter sets are found to be consistent with the empirical constraints on them as extracted from the analyses of the isospin diffusion data. The neutron-skin thickness in the $^{208}$Pb nucleus for these parameter sets of the ERMF model lie in the range of $\sim 0.20 - 0.24$ fm which is in harmony with the ones predicted by the Skyrme Hartree-Fock model. We also investigate the role of various mixed interaction terms which are crucial for the density dependence of the symmetry energy.Comment: 14 pages, 4 figures, Physical Review C (in press

Stable configurations of hybrid stars with colour-flavour-locked core

We construct static and mass-shedding limit sequences of hybrid stars, composed of colour flavour locked (CFL) quark matter core, for a set of equations of state (EOSs). The EOS for the hadronic matter is obtained using appropriately calibrated extended field theoretical based relativistic mean-field model. The MIT bag model is employed to compute the EOSs of the CFL quark matter for different values of the CFL gap parameter in the range of $50 - 150\text{MeV}$ with the deconfinement phase transition density ranging from $4\rho_0 - 6\rho_0$ ($\rho_0 = 0.16\text{fm}^{-3}$). We find, depending on the values of the CFL gap parameter and the deconfinement phase transition density, the sequences of stable configurations of hybrid stars either form third families of the compact stars or bifurcate from the hadronic sequence. The hybrid stars have masses $1.0 - 2.1 M_\odot$ with radii $9 - 13.5$ km. The maximum values of mass shedding limit frequency for such hybrid stars are $1 -2$ kHz. For the smaller values of the CFL gap parameter and the deconfinement phase transition density, mass-radius relationships are in harmony with those deduced by applying improved hydrogen atmosphere model to fit the high quality spectra from compact star X7 in the globular cluster 47 Tucanae. We observed for some cases that the third family of compact stars exist in the static sequence, but, disappear from the mass-shedding limit sequence. Our investigation suggests that the third family of compact stars in the mass-shedding limit sequence is more likely to appear, provided they have maximum mass in the static limit higher than their second family counterpart composed of pure hadronic matter.Comment: 27 pages including 10 figures. Accepted in Phys. Rev.