Thermodynamics of magnetized dense neutron-rich matter

TL;DR

This paper explores the thermodynamics, equation of state, and magnetic properties of dense neutron-rich matter in neutron stars, especially magnetars, and discusses potential observational consequences.

Contribution

It provides a detailed analysis of the thermodynamics of magnetized dense neutron matter, including the equation of state and ferromagnetic conditions, with implications for neutron star observations.

Findings

Neutron star matter exhibits significant magnetic effects on its thermodynamics.

Conditions for a ferromagnetic state in dense neutron matter are identified.

Magnetized vacuum contributions influence the star's thermodynamic properties.

Abstract

A neutron star is one of the possible end states of a massive star. It is compressed by gravity and stabilized by the nuclear degeneracy pressure. Despite its name, the composition of these objects is not exactly known. However, from the inferred densities, neutrons will most likely compose a significant fraction of the star's interior. While all neutron stars are expected to have a magnetic field, some neutron stars (''magnetars'') are much more highly magnetized than others with inferred magnetar surface magnetic field is between $10^{14}$ to $10^{15}$ gauss. While neutron stars are macroscopic objects, due to the extreme value of the stars' energy, pressure, and magnetic field the thermodynamics on the microscopic scale can be imprinted on the star's large scale behaviour. This contribution focusses on describing the thermodynamics of magnetized dense neutron matter, its equation of state and to explore conditions of a possible ferromagnetic state, contributions from the magnetized vacuum, as well as possible observational implications.