Gravitational Waves and the Maximum Spin Frequency of Neutron Stars

TL;DR

This paper argues that the observed maximum spin frequency of neutron stars can be explained by disk/magnetosphere interactions without invoking gravitational wave emission, challenging previous assumptions about neutron star spin regulation.

Contribution

It demonstrates that spin equilibrium from disk/magnetosphere interaction suffices to explain neutron star spin limits, reducing the need for gravitational wave braking mechanisms.

Findings

Spin equilibrium explains maximum neutron star spin frequencies.

No correlation between magnetic field B and X-ray luminosity Lx.

Gravitational waves are not necessary to account for observed spin limits.

Abstract

In this Letter we re-examine the idea that gravitational waves are required as a braking mechanism to explain the observed maximum spin-frequency of neutron stars. We show that for millisecond X-ray pulsars, the existence of spin equilibrium as set by the disk/magnetosphere interaction is sufficient to explain the observations. We show as well that no clear correlation exists between the neutron star magnetic field B and the X-ray outburst luminosity Lx when considering an enlarged sample size of millisecond X-ray pulsars.