Constraining Black Hole Populations in Globular Clusters using Microlensing: Application to Omega Centauri

TL;DR

This paper proposes using gravitational microlensing observations of stars in Omega Centauri to estimate the population and distribution of black holes within the cluster, providing a new method to study these elusive objects.

Contribution

It introduces a novel approach to constrain black hole populations in globular clusters through microlensing event rate analysis, applicable to Omega Centauri.

Findings

Microlensing events in Omega Centauri can be observed over years.

Such events can reveal the black hole mass spectrum and distribution.

The method offers a new way to study black hole populations in dense stellar environments.

Abstract

We estimate the rate of gravitational microlensing events of cluster stars due to black holes (BHs) in the globular cluster NGC 5139 ($\omega Cen$). Theory and observations both indicate that $\omega Cen$ may contain thousands of BHs, but their mass spectrum and exact distribution are not well constrained. In this Letter we show that one may observe microlensing events on a timescale of years in $\omega Cen$, and such an event sample can be used to infer the BH distribution. Direct detection of BHs will, in the near future, play a major role in distinguishing binary BH merger channels. Here we explore how gravitational microlensing can be used to put constraints on BH populations in globular clusters.