What is the magnetic field distribution for the equation of state of magnetized neutron stars?

Dexheimer, V.; Franzon, B.; Gomes, Renata Nascimento; Farias, Ricardo L. S.; Avancini, S. S.; Schramm, Stefan

doi:10.1016/j.physletb.2017.09.008

Cited by 54 publications

(44 citation statements)

References 45 publications

(51 reference statements)

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“…µ < 2 × 10 31 Am 2 . This smooth change of magnetic fields inside stars illustrates once more that ad-hoc exponential parametrizations for the magnetic field ) are unrealistic (as already discussed in Dexheimer et al (2017)), as they produce an increase of several orders of magnitude for the magnetic field inside the stars.…”

Section: Families Of Starsmentioning

confidence: 77%

Limiting magnetic field for minimal deformation of a magnetized neutron star

Gomes

Pais

Dexheimer

et al. 2019

A&A

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Aims. In this work, we study the structure of neutron stars under the effect of a poloidal magnetic field and determine the limiting largest magnetic field strength that induces a deformation such that the ratio between the polar and equatorial radii does not exceed 2%. We consider that, under these conditions, the description of magnetic neutron stars in the spherical symmetry regime is still satisfactory. Methods. We describe different compositions of stars (nucleonic, hyperonic, and hybrid), using three state-of-the-art relativistic mean field models (NL3ωρ, MBF, and CMF, respectively) for the microscopic description of matter, all in agreement with standard experimental and observational data. The structure of stars is described by the general relativistic solution of both Einstein's field equations assuming spherical symmetry and Einstein-Maxwell's field equations assuming an axi-symmetric deformation. Results. We find a limiting magnetic moment of the order of 2 × 10 31 Am 2 , which corresponds to magnetic fields of the order of 10 16 G at the surface and 10 17 G at the centre of the star, above which the deformation due to the magnetic field is above 2%, therefore, not negligible. We show that the intensity of the magnetic field developed in the star depends on the EoS, and, for a given baryonic mass and fixed magnetic moment, larger fields are attained with softer EoS. We also show that the appearance of exotic degrees of freedom, such as hyperons or a quark core, is disfavored in the presence of a very strong magnetic field. As a consequence, a highly magnetized nucleonic star may suffer an internal conversion due to the decay of the magnetic field, which could be accompanied by a sudden cooling of the star or a gamma ray burst.

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Section: Families Of Starsmentioning

confidence: 77%

Limiting magnetic field for minimal deformation of a magnetized neutron star

Gomes

Pais

Dexheimer

et al. 2019

A&A

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“…This discussion shows that there cannot be any correct description of the magnetic field in spherical symmetry. Starting from two-dimensional numerical models, Dexheimer et al [28,29] performed a fit to the shapes of the magnetic field profiles following the stellar polar direction as a function of the chemical potentials (as in [11]) by quadratic polynomials instead of exponential ones as…”

Section: Introductionmentioning

confidence: 99%

Magnetic field distribution in magnetars

2019

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Using an axisymmetric numerical code, we perform an extensive study of the magnetic field configurations in non-rotating neutron stars, varying the mass, magnetic field strength and the equation of state. We find that the monopolar (spherically symmetric) part of the norm of the magnetic field can be described by a single profile, that we fit by a simple eighth-order polynomial, as a function of the star's radius. This new generic profile applies remarkably well to all magnetized neutron star configurations built on hadronic equations of state. We then apply this profile to build magnetized neutron stars in spherical symmetry, using a modified Tolman-Oppenheimer-Volkov (TOV) system of equations. This new formalism produces slightly better results in terms of massradius diagrams than previous attempts to add magnetic terms to these equations. However, we show that such approaches are less accurate than usual, non-magnetized TOV models, and that consistent models must depart from spherical symmetry. Thus, our "universal" magnetic field profile is intended to serve as a tool for nuclear physicists to obtain estimates of magnetic field inside neutron stars, as a function of radial depth, in order to deduce its influence on composition and related properties. It possesses the advantage of being based on magnetic field distributions from realistic self-consistent computations, which are solutions of Maxwell's equations.

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“…In particular, for a fixed electric current amplitude configuration, the central magnetic field varies from8 10 G 17 for the z = 0.040 parameterization to1.01 10 G 18 for the z = 0.129 case. For a detailed discussion of poloidal magnetic field profiles in magnetic stars, see Dexheimer et al (2016).…”

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confidence: 99%

Many-body Forces in Magnetic Neutron Stars

Gomes

Franzon

Dexheimer

et al. 2017

ApJ

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In this work, we study in detail the effects of many-body forces on the equation of state and the structure of magnetic neutron stars. The stellar matter is described within a relativistic mean field formalism that takes into account many-body forces by means of a nonlinear meson field dependence on the nuclear interaction coupling constants. We assume that matter is at zero temperature, charge neutral, in beta equilibrium, and populated by the baryon octet, electrons, and muons. In order to study the effects of different degrees of stiffness in the equation of state, we explore the parameter space of the model, which reproduces nuclear matter properties at saturation, as well as massive neutron stars. Magnetic field effects are introduced both in the equation of state and in the macroscopic structure of stars by the self-consistent solution of the Einstein-Maxwell equations. In addition, the effects of poloidal magnetic fields on the global properties of stars, as well as density and magnetic field profiles, are investigated. We find that not only different macroscopic magnetic field distributions but also different parameterizations of the model for a fixed magnetic field distribution impact the gravitational mass, deformation, and internal density profiles of stars. Finally, we show that strong magnetic fields significantly affect the particle populations of stars.

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What is the magnetic field distribution for the equation of state of magnetized neutron stars?

Cited by 54 publications

References 45 publications

Limiting magnetic field for minimal deformation of a magnetized neutron star

Limiting magnetic field for minimal deformation of a magnetized neutron star

Magnetic field distribution in magnetars

Many-body Forces in Magnetic Neutron Stars

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