Millisecond pulsars around intermediate-mass black holes in globular clusters

TL;DR

This paper investigates the formation and detectability of millisecond pulsar and intermediate-mass black hole binaries in globular clusters, suggesting future radio telescopes could confirm IMBH presence in these environments.

Contribution

It provides the first detailed simulation-based analysis of MSP capture by IMBHs in globular clusters, highlighting formation mechanisms and observational prospects.

Findings

IMBH-MSP binaries form via stellar encounters in clusters.

Such binaries are short-lived due to gravitational wave emission.

Next-generation telescopes could detect these systems, testing IMBH hypotheses.

Abstract

We study the process of dynamical capture of a millisecond pulsar (MSP) by a single or binary IMBH, simulating various types of single-binary and binary-binary encounters. It is found that [IMBH,MSP] binaries form over cosmic time in a cluster, via encounters of wide--orbit binary MSPs off the single IMBH, and at a lower pace, via interactions of (binary or single) MSPs with the IMBH orbited by a typical cluster star. The formation of an [IMBH,MSP] system is strongly inhibited if the IMBH is orbited by a stellar mass black hole. The [IMBH,MSP] binaries that form are relatively short-lived, $\lsim 10^{8-9}$ yr, since their orbits decay via emission of gravitational waves. The detection of an [IMBH,MSP] system has a low probability of occurrence, when inferred from the current sample of MSPs in GCs. If next generation radio telescopes, like SKA, will detect an order of magnitude larger population of MSP in GCs, at least one [IMBH,MSP] is expected. Therefore, a complete search for low-luminosity MSPs in the GCs of the Milky Way with SKA will have the potential of testing the hypothesis that IMBHs of order $100 \msun$ are commonly hosted in GCs.