Modeling anisotropic magnetized White Dwarfs with $\gamma$ metric

TL;DR

This paper develops a model using the $b3$-metric to describe the structure of magnetized White Dwarfs, accounting for anisotropic pressures and shape deformation due to magnetic fields, without exceeding the Chandrasekhar mass limit.

Contribution

It introduces a new axially symmetric model linking magnetic anisotropy to the shape and structure of White Dwarfs, extending previous spherical models.

Findings

Magnetic anisotropy causes White Dwarfs to deform into spheroids.

Deformation effects are significant at low densities but do not alter maximum mass limits.

White Dwarfs' maximum mass remains below the Chandrasekhar limit despite magnetic effects.

Abstract

The effect of magnetic fields in the Equations of State (EoS) of compact objects is the splitting of the pressure in two components, one parallel and the other perpendicular to the magnetic field. This anisotropy suggests the necessity of using structure equations considering the axial symmetry of the magnetized system. In this work, we consider an axially symmetric metric in spherical coordinates, the $\gamma$-metric, and construct a system of equations to describe the structure of spheroidal compact objects. In addition, we connect the geometrical parameter $\gamma$ linked to the spheroid's radii, with the source of the anisotropy. So, the model relates the shape of the compact object to the physics that determines the properties of the composing matter. To illustrate how our structure equations work, we obtain the mass-radii solutions for magnetized White Dwarfs. Our results show that the main effect of the magnetic field anisotropy in White Dwarfs structure is to cause a deformation of these objects. Since this effect is only relevant at low densities, it does not affect the maximum values of magnetized White Dwarf's masses, which remain under Chandrasekhar limit.