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.

Impact of Nuclear Deformation on Neutron Dripline Prediction: A Study of Mg Isotopes

We have employed the relativistic Hartree-Bogoliubov (RHB) model with density-dependent meson-exchange interaction and separable pairing to investigate neutron dripline mechanisms for heavy Mg isotopes. In the present study, 40Mg is predicted to be dripline nuclei. The calculations are carried out by taking axial deformation into account. An investigation of shape transition is also done for even-even 32-42Mg isotopes. Our prediction for neutron dripline for 40Mg is consistent with some recent studies

Non-rotating and rotating neutron stars in the extended field theoretical model

We study the properties of non-rotating and rotating neutron stars for a new set of equations of state (EOSs) with different high density behaviour obtained using the extended field theoretical model. The high density behaviour for these EOSs are varied by varying the $\omega-$meson self-coupling and hyperon-meson couplings in such a way that the quality of fit to the bulk nuclear observables, nuclear matter incompressibility coefficient and hyperon-nucleon potential depths remain practically unaffected. We find that the largest value for maximum mass for the non-rotating neutron star is $2.1M_\odot$. The radius for the neutron star with canonical mass is $12.8 - 14.1$ km provided only those EOSs are considered for which maximum mass is larger than $1.6M_\odot$ as it is the lower bound on the maximum mass measured so far. Our results for the very recently discovered fastest rotating neutron star indicate that this star is supra massive with mass $1.7 - 2.7M_\odot$ and circumferential equatorial radius $12 - 19$ km.Comment: 28 pages, 12 figures. Phys. Rev. C (in press

Correlations in the properties of static and rapidly rotating compact stars

Correlations in the properties of the static compact stars (CSs) and the ones rotating with the highest observed frequency of 1122Hz are studied using a large set of equations of state (EOSs). These EOSs span various approaches and their chemical composition vary from the nucleons to hyperons and quarks in $\beta$-equilibrium. It is found that the properties of static CS, like, the maximum gravitational mass $M_{\rm max}^{\rm stat}$ and radius $R_{1.4}^{\rm stat}$ corresponding to t he canonical mass and supramassive or non-supramassive nature of the CS rotating at 1122 Hz are strongly correlated. In particular, only those EOSs yield the CS rotating at 1122Hz to be non-supramassive for which \left (\frac{M_{\rm max}^{\rm stat}}{M_\odot}\right )^{1/2} \left (\frac{10{\rm km}}{R_{1.4}^{\rm stat}})^{3/2} is greater than unity. Suitable parametric form which can be used to split the $M_{\rm max}^{\rm stat}$ $-$ $R_{1.4}^{\rm stat}$ plane into the regions of different supramassive nature of the CS rotating at 1122Hz is presented. Currently measured maximum gravitational mass 1.76$M_\odot$ of PSR J0437-4715 suggests that the CS rotating at 1122Hz can be non-supramassive provided $R_{1.4}^{\rm stat} \leqslant 12.4$ km.Comment: 13 pages, 4 figures, Appearing in Phys. Rev.

Deformation Effect on Proton Bubble Structure in N = 28 Isotones

Purpose: To study the effect of nuclear deformation on proton bubble structure of N = 28 isotones and and compare it with the spherical limits. The reduction of depletion fraction due to deformation can be explained by studying the relative differences in the central densities.Methods: In this work, we have employed relativistic Hartree-Bogoliubov (RHB) model withdensity-dependent meson-exchange (DD-ME2) interaction and separable pairing interaction. We have performed axially constrained calculations to investigate the deformed proton bubble structure in 40Mg, 42Si, 44S, and 46Ar, isotones of N = 28 shell closure.Results: We have observed that the nuclear deformation play againsts the formation of bubble structure. In the spherical limits, the isotones of N = 28 shell closure have pronounced bubble structure with large value of depletion fraction. But, the increase in deformation leads to the disappearance of bubble structure. The internal densities in deformed nuclei are found to increase with deformation which can be related to the decrease in depletion fraction.Conclusion: By using RHB model, we have investigated the ground state and proton bubble structure of N = 28 isotones. In 44S, and 46Ar, the 2s1/21d3/2 states get inverted due to the weakning of spin-orbit strength. Due to strong dynamical correlations, arising from deformation, the central depletion of proton density is greatly affected in these isotones. The decrease in depletion fraction can be related to increase in the internal density due to deformatio

Nuclear shape evolution and shape coexistence in Zr and Mo isotopes

The phenomena of shape evolution and shape coexistence in even-even $^{88-126}$Zr and $^{88-126}$Mo isotopes is studied by employing covariant density functional theory (CDFT) with density-dependent point coupling parameter sets DD-PCX and DD-PC1, and with separable pairing interaction. The results for rms deviation in binding energies, two-neutron separation energy, the differential variation of two-neutron separation energy, and rms charge radii, as a function of neutron number, are presented and compared with available experimental data. In addition to the oblate-prolate shape coexistence in $^{96-110}$Zr isotopes, the correlation between shape transition and discontinuity in the observables are also examined. A smooth trend of charge radii in Mo isotopes is found to be due to the manifestation of triaxiality softness. The observed oblate and prolate minima are related to the low single-particle energy level density around the Fermi level of neutron and proton respectively. The present calculations also predict a deformed bubble structure in $^{100}$Zr isotope.Comment: this preprint contains incomplete data and some mistake