Observing complete gravitational wave signals from dynamical capture binaries

TL;DR

This paper evaluates the detectability of gravitational waves from highly eccentric binary systems, highlighting the need for specialized search methods as traditional templates may miss these signals.

Contribution

It introduces a simplified model for eccentric binary mergers using a Kerr metric approach and assesses their detectability with current and future gravitational wave detectors.

Findings

Most eccentric binaries will be missed by current burst searches.

Eccentric templates or stacked excess power searches are necessary.

Previous null results do not exclude eccentric binary signals.

Abstract

We assess the detectability of the gravitational wave signals from highly eccentric compact binaries. We use a simple model for the inspiral, merger, and ringdown of these systems. The model is based on mapping the binary to an effective single black hole system described by a Kerr metric, thereby including certain relativistic effects such as zoom-whirl-type behavior. The resultant geodesics source quadrupolar radiation and, in turn, are evolved under its dissipative effects. At the light ring, we attach a merger model that was previously developed for quasicircular mergers but also performs well for eccentric mergers with little modification. We apply this model to determine the detectability of these sources for initial, Enhanced, and Advanced LIGO across the parameter space of nonspinning close capture compact binaries. We conclude that, should these systems exist in nature, the vast majority will be missed by conventional burst searches or by quasicircular waveform templates in the advanced detector era. Other methods, such as eccentric templates or, more practically, a stacked excess power search, must be developed to avoid losing these sources. These systems would also have been missed frequently in the initial LIGO data analysis. Thus, previous null coincidence results with detected gamma-ray bursts cannot exclude the possibility of coincident gravitational wave signals from eccentric binaries.