Degeneracy of gravitational waveforms in the context of GW150914

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 m₁ = 36⁺⁵₋₄ M_⊙ and m₂ = 29⁺⁴₋₄ M_⊙, 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 m₁ = 70 M_⊙ and m₂ = 35 M_⊙, and strong anti-aligned spins (χ₁ = 0.95 and χ₂ = −0.95) yield almost the same signal-to-noise ratio in the strain data for GW150914.