Continuous Gravitational Waves and Magnetic Monopole Signatures from Single Neutron Stars

TL;DR

This paper explores how magnetic monopoles could influence gravitational wave signals from neutron stars, proposing that their presence might produce detectable signatures in early-stage continuous gravitational waves, especially from magnetars.

Contribution

It introduces a novel idea that magnetic monopoles could leave imprints on gravitational wave emissions from neutron stars, linking exotic particle physics with astrophysical observations.

Findings

Magnetic monopoles could affect neutron star quadrupole ellipticity.

Early-stage gravitational wave signals might show signatures of monopoles.

Magnetars are promising candidates for detecting these effects.

Abstract

Future observations of continuous gravitational waves from single neutron stars, apart from their monumental astrophysical significance, could also shed light on fundamental physics and exotic particle states. One such avenue is based on the fact that magnetic fields cause deformations of a neutron star, which results in a magnetic-field-induced quadrupole ellipticity. If the magnetic and rotation axes are different, this quadrupole ellipticity may generate continuous gravitational waves which may last decades, and may be observable in current or future detectors. Light, milli-magnetic monopoles, if they exist, could be pair-produced non-perturbatively in the extreme magnetic fields of neutron stars, such as magnetars. This non-perturbative production furnishes a new, direct dissipative mechanism for the neutron star magnetic fields. Through their consequent effect on the magnetic-field-induced quadrupole ellipticity, they may then potentially leave imprints in the early stage continuous gravitational wave emissions. We speculate on this possibility in the present study, by considering some of the relevant physics and taking a very simplified toy model of a magnetar as the prototypical system. Preliminary indications are that new-born millisecond magnetars could be promising candidates to look for such imprints. Deviations from conventional evolution, and comparatively abrupt features in the early stage gravitational waveforms, distinct from other astrophysical contributions, could be distinguishable signatures for these exotic monopole states.