Neutron stars in a perturbative $f(R)$ gravity model with strong magnetic fields

TL;DR

This paper explores how strong magnetic fields and a perturbative $f(R)$ gravity model influence neutron star structure, showing that certain parameter combinations can support neutron stars exceeding 2 solar masses.

Contribution

It introduces a combined analysis of strong magnetic fields and $f(R)$ gravity effects on neutron stars, revealing conditions for high-mass neutron stars with soft equations of state.

Findings

Strong magnetic fields significantly affect the neutron star equation of state.

Modified gravity allows soft equations of state to support >2 solar mass neutron stars.

Parameter space identified where magnetic fields and gravity modifications enable massive neutron stars.

Abstract

We investigate the effect of a strong magnetic field on the structure of neutron stars in a model with perturbative $f(R)$ gravity. The effect of an interior strong magnetic field of about $10^{17 \sim 18}$ G on the equation of state is derived in the context of a quantum hadrodynamics (QHD) model. We solve the modified spherically symmetric hydrostatic equilibrium equations derived for a gravity model with $f(R)=R+\alpha R^2$. Effects of both the finite magnetic field and the modified gravity are detailed for various values of the magnetic field and the perturbation parameter $\alpha$ along with a discussion of their physical implications. We show that there exists a parameter space of the modified gravity and the magnetic field strength, in which even a soft equation of state can accommodate a large ($> 2$ M$_\odot$) maximum neutron star mass through the modified mass-radius relation.