Degeneracy of gravitational waveforms in the context of GW150914

TL;DR

This paper investigates the degeneracy of gravitational waveforms from binary black hole mergers, revealing that different mass and spin configurations can produce nearly indistinguishable signals, impacting parameter estimation accuracy.

Contribution

It demonstrates extensive waveform degeneracy in the parameter space, showing that high-mass and high-spin configurations can mimic the GW150914 signal, challenging previous parameter estimates.

Findings

High cross-correlations across broad parameter regions

Uncertainties exceed LIGO's Bayesian analysis

Degeneracy includes high-mass, high-spin configurations

Abstract

We study the degeneracy of theoretical gravitational waveforms for binary black hole mergers using an aligned-spin effective-one-body model. After appropriate truncation, bandpassing, and matching, we identify regions in the mass--spin parameter space containing waveforms similar to the template proposed for GW150914, with masses $m_1 = 36^{+5}_{-4} M_\odot$ and $m_2 = 29^{+4}_{-4} M_\odot$, using the cross-correlation coefficient as a measure of the similarity between waveforms. Remarkably high cross-correlations are found across broad regions of parameter space. The associated uncertanties exceed these from LIGO's Bayesian analysis considerably. We have shown that waveforms with greatly increased masses, such as $m_1 = 70 M_\odot$ and $m_2 = 35 M_\odot$, and strong anti-aligned spins ($\chi_1=0.95$ and $\chi_2=-0.95$) yield almost the same signal-to-noise ratio in the strain data for GW150914.