Uniformly rotating neutron stars in the global and local charge neutrality cases

TL;DR

This paper models uniformly rotating neutron stars considering both global and local charge neutrality, using generalized Einstein-Maxwell-Thomas-Fermi equations, and analyzes their equilibrium configurations and physical properties.

Contribution

It introduces a comprehensive relativistic model for rotating neutron stars with global charge neutrality, extending previous work to include rotation and detailed physical property calculations.

Findings

Maximum and minimum neutron star masses and rotation frequencies identified.

Differences between global and local charge neutrality cases analyzed.

Equilibrium configurations characterized by mass, radius, moment of inertia, and quadrupole moment.

Abstract

In our previous treatment of neutron stars, we have developed the model fulfilling global and not local charge neutrality. In order to implement such a model, we have shown the essential role by the Thomas-Fermi equations, duly generalized to the case of electromagnetic field equations in a general relativistic framework, forming a coupled system of equations that we have denominated Einstein-Maxwell-Thomas-Fermi (EMTF) equations. From the microphysical point of view, the weak interactions are accounted for by requesting the \beta\ stability of the system, and the strong interactions by using the \sigma-\omega-\rho\ nuclear model, where \sigma, \omega\ and \rho\ are the mediator massive vector mesons. Here we examine the equilibrium configurations of slowly rotating neutron stars by using the Hartle formalism in the case of the EMTF equations indicated above. We integrate these equations of equilibrium for different central densities and circular angular velocities and compute the mass, polar and equatorial radii, angular momentum, eccentricity, moment of inertia, as well as quadrupole moment of the configurations. Both the Keplerian mass-shedding limit and the axisymmetric secular instability are used to construct the new mass-radius relation. We compute the maximum and minimum masses and rotation frequencies of neutron stars. We compare and contrast all the results for the global and local charge neutrality cases.