Repeated Bursts from Relativistic Scattering of Compact Objects in Galactic Nuclei

TL;DR

This paper investigates the gravitational wave signals from highly eccentric binary systems in galactic nuclei, highlighting the detectability of repeated bursts and their significance for current and future observatories.

Contribution

It introduces a detailed analysis of repeated burst signals from relativistic scattering events, emphasizing their detectability and the robustness of PN templates during the burst phase.

Findings

Repeated bursts can produce significant SNR for LIGO detection.

RB phase signals are broadband and detectable across multiple frequency bands.

Detection range extends to 200-600 Mpc depending on the binary type.

Abstract

Galactic nuclei are densely populated by stellar mass compact objects such as black holes and neutron stars. Bound, highly eccentric binaries form as a result of gravitational wave (GW) losses during close flybys between these objects. We study the evolution of these systems using 2.5 and 3.5 order post-Newtonian equations of motion. The GW signal consists of many thousand repeated bursts (RB) for minutes to days (depending on the impact parameter and masses), followed by a powerful GW chirp and an eccentric merger. We show that a significant signal to noise ratio (SNR) accumulates already in the RB phase, corresponding to a detection limit around 200-300 Mpc and 300--600 Mpc for Advanced LIGO for an average orientation BH/NS or BH/BH binary, respectively. The theoretical errors introduced by the inaccuracy of the PN templates are typically much less severe for the RB phase than in the following eccentric merger. The GW signal in the RB phase is broadband; we show that encounters involving intermediate mass black holes are detectable in multiple frequency bands coincidentally using LIGO and LISA.