Dynamical Formation of Millisecond Pulsars in Globular Clusters

TL;DR

This study compares the luminosity distributions of millisecond pulsars in globular clusters and the Galactic field, revealing different formation histories and highlighting the role of stellar interactions in clusters.

Contribution

It demonstrates that MSPs in globular clusters have a steeper luminosity distribution slope and establishes a link between MSP populations and cluster properties like encounter rate and metallicity.

Findings

MSPs in GCs have a steeper luminosity distribution slope ($q=-0.83$) than in the Galactic field ($q=-0.48$).

Positive correlations exist between MSP populations and cluster encounter rate and metallicity.

Stellar dynamical interactions are important in MSP formation in globular clusters.

Abstract

The cumulative luminosity distribution functions (CLFs) of radio millisecond pulsars (MSPs) in globular clusters (GCs) and in the Galactic field at a frequency of 1.4 GHz have been examined. Assuming a functional form, $N \propto L^q$ where $N$ is the number of MSPs and $L$ is the luminosity at 1.4 GHz, it is found that the CLFs significantly differ with a steeper slope, $q=-0.83 \pm 0.05$, in GCs than in the Galactic field ($q=-0.48 \pm 0.04$), suggesting a different formation or evolutionary history of MSPs in these two regions of the Galaxy. To probe the production mechanism of MSPs in clusters, a search of the possible relationships between the MSP population and cluster properties was carried out. The results of an investigation of 9 GCs indicate positive correlations between the MSP population and the stellar encounter rate and metallicity. This provides additional evidence suggesting that stellar dynamical interactions are important in the formation of the MSP population in GCs.