Effect of magnetic field on the burning of a neutron star

TL;DR

This paper investigates how strong magnetic fields influence the phase transition from nuclear to quark matter in neutron stars, affecting their magnetic properties and potential observational signatures.

Contribution

It introduces a relativistic MHS framework to analyze the phase transition and magnetic field evolution during neutron star conversion to quark stars.

Findings

Shock-induced phase transition occurs at densities >3 times nuclear saturation density.

Conversion from neutron star to quark star is exothermic at high densities.

Magnetic field and tilt angle of the star are significantly affected by the phase transition and infalling matter velocities.

Abstract

In this article, we present the effect of a strong magnetic field in the burning of a neutron star (NS). We have used relativistic magneto-hydrostatic (MHS) conservation equations for studying the PT from nuclear matter (NM) to quark matter (QM). We found that the shock-induced phase transition (PT) is likely if the density of the star core is more than three times nuclear saturation ($\rho_s$) density. The conversion process from NS to quark star (QS) is found to be an exothermic process beyond such densities. The burning process at the star center most likely starts as a deflagration process. However, there can be a small window at lower densities where the process can be a detonation one. At small enough infalling matter velocities the resultant magnetic field of the QS is lower than that of the NS. However, for a higher value of infalling matter velocities, the magnetic field of QM becomes larger. Therefore, depending on the initial density fluctuation and on whether the PT is a violent one or not the QS could be more magnetic or less magnetic. The PT also have a considerable effect on the tilt of the magnetic axis of the star. For smaller velocities and densities the magnetic angle are not affected much but for higher infalling velocities tilt of the magnetic axis changes suddenly. The magnetic field strength and the change in the tilt axis can have a significant effect on the observational aspect of the magnetars.