Mass-Radius relationship of Strongly Magnetized Super-Chandrasekhar Anisotropic Deformed White Dwarf Stars in presence of $γ$-metric

Abstract: The masses and radii of strongly magnetized anisotropic deformed white dwarf stars are investigated using the stellar structure equations in the parameterized $\gamma$-metric formalism. The Equation of State (EoS) of a completely degenerate relativistic electron gas in strong quantizing density-dependent magnetic field is developed. The fluid and field pressure anisotropy among the parallel and perpendicular components to the magnetic field is taken into consideration. This anisotropy in the EoS causes axisymmetric deformation of the star. We found stable solutions of deformed super-Chandrasekhar ultramassive white dwarfs. The masses of anisotropic magnetized white dwarfs at the same central density decrease monotonically with the increase in the strength of the central magnetic field, while the equatorial radii increase monotonically. This is in sharp contrast to the isotropic case where both the mass and radius increase monotonically. High magnetic field increases anisotropy and oblateness. We also see that the maximum mass and its corresponding equatorial radius both decrease as central magnetic field strength increases. We also notice that the maximum mass occurs at higher central density as the magnetic field increases. This shows that increasing magnetic field (hence increasing anisotropy) softens the EoS and makes the star more compact.