Effects of anisotropy on strongly magnetized neutron and strange quark stars in general relativity

Abstract

We investigate the properties of anisotropic, spherically symmetric compact stars, especially neutron stars and strange quark stars, made of strongly magnetized matter. The neutron stars are described by SLy equation of state, the strange quark stars by an equation of state based on the MIT Bag model. The stellar models are based on an a priori assumed density dependence of the magnetic field and thus anisotropy. Our study shows that not only the presence of a strong magnetic field and anisotropy, but also the orientation of the magnetic field itself, have an important influence on the physical properties of stars. Two possible magnetic field orientations are considered, a radial orientation, where the local magnetic fields point in the radial direction, and a transverse orientation, where the local magnetic fields are perpendicular to the radial direction. Interestingly, we find that for a transverse orientation of the magnetic field, the stars become more massive with increasing anisotropy and magnetic field strength and increase in size, since the repulsive, effective anisotropic force increases in this case. In the case of a radially orientated magnetic field, however, the masses and radii of the stars decrease with increasing magnetic field strength, because of the decreasing effective anisotropic force. Importantly, we also show that in order to achieve hydrostatic equilibrium configurations of magnetized matter, it is essential to account for both the local anisotropy effects as well as the anisotropy effects caused by a strong magnetic field. Otherwise, hydrostatic equilibrium is not achieved for magnetized stellar models.

17 pages including 13 figures and 4 tables; accepted for publication in The Astrophysical Journal (ApJ)

References in corpus (25)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• GW190814: Gravitational Waves from the Coalescence of a 23 M${}_{\odot }$ Black Hole with a 2.6 M${}_{\odot }$ Compact Object
• Physics of Strongly Magnetized Neutron Stars
• Equation of State of a Dense and Magnetized Fermion System
• Quark matter under strong magnetic fields in the Nambu--Jona-Lasinio Model
• Electrically Charged Strange Quark Stars
• New mass limit for white dwarfs: super-Chandrasekhar type Ia supernova as a new standard candle
• The Strange Star Surface: A Crust with Nuggets
• Possible Evidence for Free Precession of a Strongly Magnetized Neutron Star in the Magnetar 4U 0142+61
• A comparison of Hořava-Lifshitz gravity and Einstein gravity through thin-shell wormhole construction
• Magnetized strange quark matter and magnetized strange quark stars
• Strongly magnetized cold electron degenerate gas: Mass-radius relation of the magnetized white dwarf
• Stellar matter with a strong magnetic field within density-dependent relativistic models
• Quark magnetar in three-flavor Nambu--Jona-Lasinio model with vector interaction and magnetized gluon potential
• Modified Einstein's gravity as a possible missing link between sub- and super-Chandrasekhar type Ia supernovae
• Quark stars under strong magnetic fields
• Properties of High-Density Matter in Neutron Stars
• GRMHD formulation of highly super-Chandrasekhar magnetized white dwarfs: stable configurations of non-spherical white dwarfs
• Equation of state of strongly magnetized matter with hyperons and $\Delta$-resonances
• Magnetized strange quark matter in a mass-density-dependent model
• Regularization of the Nambu-Jona Lasinio model under a uniform magnetic field and the role of the anomalous magnetic moments
• Revised density of magnetized nuclear matter at the neutron drip line
• Maximum Mass of Hybrid Stars in the Quark Bag Model