Thermal Evolution and Axion Emission Properties of Strongly Magnetized Neutron Stars

TL;DR

This study investigates how intense magnetic fields influence the thermal evolution, emission properties, and axion mass bounds of strongly magnetized neutron stars by modeling their structure and cooling behavior.

Contribution

It introduces a detailed model of neutron star structure with magnetic fields and analyzes their impact on cooling rates and emission luminosities, including axions.

Findings

Magnetic fields significantly alter neutron star cooling rates.

Luminosities of neutrinos, axions, and photons are affected by magnetic fields.

The axion mass bound increases slightly due to magnetic field effects.

Abstract

Emission properties of compact astrophysical objects such as Neutron stars (NSs) are associated with crucial astronomical observables. In the current work, we obtain the mass, pressure profiles of the non-rotating NSs using the modified Tolman Oppenheimer Volkoff (TOV) system of equations in the presence of intense magnetic field. We obtain the profiles by using a specific distance-dependent magnetic field in the modified TOV equations. We employ three different equations of states (EoS) to solve the TOV equations by assuming the core of NSs comprises a hadronic matter. Employing the above profiles, we determine the cooling rates of spherically symmetric NSs as a function of time with and without including the magnetic field using the NSCool code. We have also determined the cooling rates as a function of radius for three different NSs. Furthermore, we determine the luminosity of neutrinos, axions, and photons emitting from the NSs in the presence and absence of a magnetic field for an axion mass $16$ meV and three different EoS. Our comparative study indicates that the cooling rate and luminosities of neutrinos, axions, and photons change significantly due to the impact of the strong magnetic field. We also find that due to the magnetic field, the axion mass bound increases slightly compared to without a magnetic field..