Heavy Magnetic Neutron Stars

TL;DR

This paper investigates how magnetic fields influence the structure and maximum mass of neutron stars with nucleonic and hyperonic matter using density-dependent relativistic mean field models, considering astrophysical constraints.

Contribution

It introduces a comprehensive analysis of magnetic effects on hyperonic and nucleonic neutron stars within DD-RMF models, highlighting magnetic field impact on star mass and composition.

Findings

Pure nucleonic stars can meet GW190814 mass constraints without magnetic fields.

Strong magnetic fields cause hyperonic matter to stiffen and produce more massive stars.

Magnetic fields induce large deformations in neutron stars, affecting their shape and stability.

Abstract

We systematically study the properties of pure nucleonic and hyperonic magnetic stars using a density-dependent relativistic mean field (DD-RMF) equations of state. We explore several parameter sets and hyperon coupling schemes within the DD-RMF formalism. We focus on sets that are in better agreement with nuclear and other astrophysical data, while generating heavy neutron stars. Magnetic field effects are included in the matter equation of state and in general relativity solutions, which in addition fulfill Maxwell's equations. We find that pure nucleonic matter, even without magnetic field effects, generates neutron stars that satisfy the potential GW190814 mass constraint; however, this is not the case for hyperonic matter, which instead only satisfies the more conservative 2.1 M$_{\odot}$ constraint. In the presence of strong but still somehow realistic internal magnetic fields $\approx10^{17}$ G, the stellar charged particle population re-leptonizes and de-hyperonizes. As a consequence, magnetic fields stiffen hyperonic equations of state and generate more massive neutron stars, which can satisfy the possible GW190814 mass constraint but present a large deformation with respect to spherical symmetry.