The influence of Strong Magnetic Field in Hyperonic Neutron Stars

TL;DR

This paper investigates how strong magnetic fields influence the equation of state of hyperonic neutron stars, showing that magnetic fields can produce more massive neutron stars consistent with observations.

Contribution

It introduces a relativistic model including hyperons and strong magnetic fields to analyze their combined effect on neutron star mass and structure.

Findings

Strong magnetic fields increase neutron star maximum mass.

Hyperonic matter softens the EoS but magnetic fields counteract this effect.

Magnetic fields enable the formation of neutron stars with masses around 2 solar masses.

Abstract

The physics of neutron stars leads historically towards Landau's speculation. Even before the discovery of the neutron, he postulated the possible existence of stars more compact than white dwarfs, containing matter of the order of nuclear density. From a modern point of view neutron stars are compact objects maintained by the equilibrium between gravity and the degeneracy pressure of the fermions together with a strong nuclear repulsion force due to the high density reached in their interior. While the physics in the vicinity of nuclear saturation density is well know from phenomenology, the physics of ultra-dense nuclear matter is still an open puzzle. In this work we study dense nuclear matter within a relativistic model, allowing hyperons to be present through beta equilibrium. The presence of hyperons is justifiable since the constituents of neutron stars are fermions. So, according to the Pauli principle, as the baryon density increases, so do the Fermi momentum and the Fermi energy. On the other hand, this hyperonic matter softens the equation of state (EoS) and a recent measurement of pulsar PSR J1614-2230 implies that the EoS has to be stiff enough to produce a 2.0 $M_{\odot}$ pulsar. We also consider Duncan's magnetar ideas and study the influence of strong magnetic fields on the EoS. We see that a strong magnetic field produces very massive neutron stars, in agreement with the astronomical observations.