Abstract

In this work, we study the effects of different magnetic field configurations in neutron stars described by a many-body forces formalism (MBF model). The MBF model is a relativistic mean field formalism that takes into account many-body forces by means of a meson field dependence of the nuclear interaction coupling constants. We choose the best parametrization of the model that reproduces nuclear matter properties at saturation and also describes massive neutron stars. We assume matter to be in beta-equilibrium, charge neutral and at zero temperature. Magnetic fields are taken into account both in the equation of state and in the structure of the stars by the self-consistent solution of the Einstein-Maxwell equations. We assume a poloidal magnetic field distribution and calculate its effects on neutron stars, showing its influence on the gravitational mass and deformation of the stars.

Highlights

  • Magnetars appear in nature in the form of Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs)

  • We use the equation of state (EoS) of the MBF model as an input to calculate the strucuture of the magnetic stars, following the formalism presented in the last section

  • Note that such calculations are self-consistent, as we are taking into account magnetic effects both on the EoS and on the star structure

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Summary

Introduction

Magnetars (neutron stars powered by their magnetic energy reservoirs) appear in nature in the form of Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) Such objects possess surface magnetic fields up to around B ∼ 1015 G, and are usually associated to neutron stars. Magnetic effects were studied in the past in the equation of state (EoS), through Landau quantization of the particles energy levels, in different nuclear models in order to describe hyperon stars 4–11, quark stars 12–18 and hybrid stars 19,20. In order to calculate the macroscopic structure of highly magnetized neutron stars, one has to solve the Einstein-Maxwell coupled equations using a non spherical metric Such a formalism was implemented in the past by Bonazzola et al among others 2,21,22 and only recently applied to self-consistently include magnetic effects both in the EoS and structure of quark 23 and hybrid stars 24. The Landau number ranges from zero to a maximum value which avoids the particles Fermi momenta to become imaginary at zero temperature (see more details in Ref. 27)

The Structure of Magnetic Stars
Br2 sin θ
Results and Discussion
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