Rotating neutron stars with chaotic magnetic fields in general relativity and Rastall gravity

TL;DR

This study models rotating neutron stars with chaotic magnetic fields in both general relativity and Rastall gravity, revealing how magnetic fields and Rastall parameters influence stellar structure and observable properties.

Contribution

It extends the Hartle-Thorne formalism to Rastall gravity and incorporates magnetic fields coupled to energy density, providing new insights into neutron star properties under alternative gravity theories.

Findings

Magnetic fields can increase the maximum neutron star mass.

Higher magnetic fields and Rastall parameters reduce stellar radii at low masses.

Magnetic fields can increase the moment of inertia within certain mass ranges.

Abstract

Observations indicate that the magnetic fields on neutron stars (NSs) lie in the range of $10^{8}$-$10^{15}$ G. We investigate rotating NSs with chaotic magnetic fields in both general relativity (GR) and Rastall gravity (RG). The equation of state (EOS) of NS matter is formulated within the framework of quantum hadrodynamics (QHD). The Hartle-Thorne formalism, extended to RG, is employed as an approximation for describing rotating NSs, while the magnetic field is modeled through an ansatz in which it is coupled to the energy density. We find that at high masses, neither rotation nor the Rastall parameter significantly affects the total mass, whereas the magnetic field strength can increase the maximum allowed mass. At lower masses, both the magnetic field and an increasing Rastall parameter reduce the stellar radius in the static configuration. Although higher angular velocities enhance stellar deformation, both magnetic field and larger Rastall parameter tend to suppress it. Regarding the moment of inertia, the Rastall parameter has little impact, whereas the magnetic field strength can increase it within the mass range $1.50$-$1.99 M_\odot$. All parameters considered in this study are consistent with observational constraints on the moment of inertia obtained from radio observations of massive pulsars.