Detecting gravitational waves from dynamical capture binaries

Abstract

In dense stellar regions, highly-eccentric binaries of black holes and neutron stars can form through dynamical capture. This occurs when a pair of objects lose sufficient energy during a close encounter to gravitational radiation or tidal effects, thus forming a bound system. These eccentric compact object binaries are expected to undergo a repeating burst inspiral phase, during which a sequence of gravitational wave bursts are emitted. Unfortunately, current gravitational wave searches are ill-suited to detecting these signals. In this work, we present a novel "power stacking" method for the detection of gravitational wave signals from dynamical capture binaries. We implement this method as an extension of the Q-transform, a projection onto a multiresolution basis of windowed complex exponentials that has been used to analyze data from the network of Laser Interferometer Gravitational-wave Observatory (LIGO) detectors. Our method searches for excess power over an ensemble of time-frequency tiles. This ensemble is identified using a model of the complete inspiral-merger-ringdown waveform of dynamical capture binaries. We characterize the performance of our method using Monte Carlo experiments with signals injected in simulated detector noise. Our results indicate that the power stacking method achieves greater sensitivity to eccentric binary signals than existing localized burst searches.