The Observed Spin Distributions of Millisecond Radio and X-ray Pulsars

TL;DR

This paper analyzes the spin distributions of various neutron star types, revealing differences between isolated and binary millisecond pulsars, and suggests age as a possible factor influencing these distributions.

Contribution

It provides the first comparative analysis of spin distributions across multiple neutron star populations, highlighting differences and potential evolutionary explanations.

Findings

Binary pulsars are generally faster spinning than isolated ones.

Spin distributions differ significantly in globular clusters.

Older age may explain the slower spins of isolated pulsars.

Abstract

We consider the currently observed spin distributions of various types of neutron stars, including isolated and binary radio millisecond pulsars in the Galactic plane and globular cluster system as well as neutron stars in low-mass X-ray binary systems where the spin rate is known either through coherent pulsations or burst oscillations. We find that the spin distributions of isolated and binary radio millisecond pulsars are statistically different, at least for those residing in globular clusters, with the binary pulsars being on average faster spinning. This result is likely to hold despite observational biases still affecting the observed spin distribution. A possible explanation for this is that the isolated radio millisecond pulsars are on average older than those in binary systems.