Single Millisecond Pulsars from Dynamical Interaction Processes in Dense Star Clusters

Abstract

Globular clusters (GCs) are particularly efficient at forming millisecond pulsars. Among these pulsars, about half lack a companion star, a significantly higher fraction than in the Galactic field. This fraction increases further in some of the densest GCs, especially those that have undergone core collapse, suggesting that dynamical interaction processes play a key role. For the first time, we create N-body models that reproduce the ratio of single-to-binary pulsars in Milky-Way-like GCs. We focus especially on NGC 6752, a typical core-collapsed cluster with many observed millisecond pulsars. Previous studies suggested that an increased rate of neutron star binary disruption in the densest clusters could explain the overabundance of single pulsars in these systems. Here, we demonstrate that binary disruption is ineffective and instead we propose that two additional dynamical processes play the dominant role: (1) tidal disruption of main-sequence stars by neutron stars; and (2) gravitational collapse of heavy white-dwarf-binary merger remnants. Neutron stars formed through these processes may also be associated with fast radio bursts similar to those observed recently in an extragalactic GC.

19 pages, 12 figures, 4 tables. Published at ApJ

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• FAST Discovery of Eight Isolated Millisecond Pulsars in NGC 6517
• Lower-mass-gap Black Holes in Dense Star Clusters
• The FAST Globular Cluster Pulsar Survey (GC FANS)
• Predicting the rate of fast radio bursts in globular clusters from binary black hole observations
• Discovery of a millisecond pulsar associated with Terzan 6