Gravitational Waves from Black-Hole Encounters: Prospects for Ground- and Galaxy-Based Observatories

TL;DR

This paper explores the potential for detecting gravitational waves from close hyperbolic black hole encounters using ground-based and pulsar timing array observatories, highlighting their sensitivity and detection prospects.

Contribution

It provides a detailed analysis of the detectable parameter space for gravitational wave bursts from black hole encounters, incorporating relativistic effects up to third post-Newtonian order.

Findings

Ground-based observatories can detect events up to megaparsec distances.

Pulsar timing arrays can constrain supermassive black hole encounters up to gigaparsec scales.

Waveform models ensure validity for close encounter scenarios.

Abstract

Close hyperbolic encounters of black holes (BHs) generate certain Burst With Memory (BWM) events in the frequency windows of the operational, planned, and proposed gravitational wave (GW) observatories. We present detailed explorations of the detectable parameter space of such events that are relevant for the LIGO-Virgo-KAGRA and the International Pulsar Timing Array (IPTA) consortia. The underlying temporally evolving GW polarization states are adapted from Cho et al. [Phys. Rev. D 98, 024039 (2018)] and therefore incorporate general relativistic effects up to the third post-Newtonian order. Further, we provide a prescription to ensure the validity of our waveform family while describing close encounters. Preliminary investigations reveal that optimally placed BWM events should be visible to megaparsec distances for the existing ground-based observatories. In contrast, maturing IPTA datasets should be able to provide constraints on the occurrences of such hyperbolic encounters of supermassive BHs to gigaparsec distances.