Stationary, axisymmetric neutron stars with meridional circulation in general relativity

Abstract

We present the first stationary, axisymmetric neutron star models with meridional circulation in general relativity. For that purpose, we developed generally rotating neutron star, a new code based on a fixedpoint iteration. We find a two-dimensional set of meridional circulation modes, which differ by the number of vortices in the stream lines of the neutron star fluid. For expected maximal meridional circulation velocities of about 1000 km=s, the vortices cause surface deformations of about a percent. The deformations depend on the shape of the vortices close to the surface and increase with the meridional circulation velocity. We also computed models of rotating neutron stars with meridional circulation, where neither the surface rotates nor does the rotation velocity exceed the circulation velocity.

Differentially-rotating neutron star models with a parametrized rotation profile

“…The centrifugal deformation and general relativistic gravity make these investigations fully reliant on numerical methods. Since the pioneering work of Butterworth & Ipser (1976), these studies have included progressively more sophisticated aspects, such as nuclear-matter equation of state (EOS), degrees of differential rotation, magnetic fields, and quite recently meridional flows (Birkl et al 2011) 1 . However, we note that all of these studies have used just a single kind of ansatz on the rotational angular velocity profile (namely the "j-const.…”

Equilibrium solutions of relativistic rotating stars with mixed poloidal and toroidal magnetic fields

“…A proposed formulation for computing non-circular spacetimes invokes a 2+1+1 spacetime decomposition [24,25]. Here, instead of this formulation, we use the one developed in [26], which is based on a 3+1 decomposition and has been successfully applied for computing waveless initial data for binary neutron stars (BNS) [27].…”

“…Such noncircular spacetimes have been calculated in the slow rotation and weak magnetic field limit as in [11][12][13], and in the fully nonlinear regime for non-magnetized compact star with large meridional flow in [24]. A proposed formulation for computing non-circular spacetimes invokes a 2+1+1 spacetime decomposition [24,25].…”

Magnetohydrodynamics in stationary and axisymmetric spacetimes: A fully covariant approach

“…(6.49) and substituted in (6.48), so that the system reduces to a single equation for f . An equivalent formulation has been developed recently by Birkl et al [57] for the barotropic case (S = 0), using the function ψ := − E(f ) df instead of f . In the Newtonian limit [cf.…”

“…A wide class of equilibrium configurations is obtained by assuming 57) withT is a function of Υ such that…”