A study of the Inspiral-Merger-Ringdown Consistency Test with gravitational-wave signals from compact binaries in eccentric orbits

The Inspiral Merger Ringdown Consistency Test (IMRCT) is one among a battery of tests of general relativity (GR) employed by the LIGO-Virgo-KAGRA (LVK) collaboration. It is used to search for deviations from GR in detected gravitational waves (GWs) from compact binary coalescences (CBCs) in a model-agnostic way. The test compares source parameter estimates extracted independently from the inspiral and post-inspiral portions of the CBC signals and, therefore, crucially relies on the accurate modeling of the waveform. Current implementations of the IMRCT routinely use quasicircular waveforms, under the assumption that the residual eccentricity of the binary when the emitted GWs enter the frequency band of the LVK detector network will be negligible. In this work, we perform a detailed study to investigate the typical magnitudes of this residual eccentricity that could potentially lead to spurious violations of the IMRCT. To that end, we conduct injection campaigns for a range of eccentricities and recover with both quasicircular and eccentric waveforms. We find that an eccentric GW signal from a GW150914-like system with $e_{\text{gw}} \gtrsim$ 0.04 at an orbit averaged frequency $\langle f_{\text{ref}} \rangle=$ 25 Hz breaks the IMRCT if recovered with quasicircular waveforms at $\gtrsim 68\%$ confidence. The violation becomes more severe ($\gtrsim 90\%$ confidence) for $e_{\text{gw}} =$ 0.055 at $\langle f_{\text{ref}} \rangle=$ 25 Hz. On the other hand, when eccentric waveforms are used, the IMRCT remains intact for all eccentricities considered. We also briefly investigate the effect of the magnitude and orientation (aligned/antialigned) of the component spins of the binary on the extent of the spurious violations of the IMRCT. Our work, therefore, demonstrates the need for accurate eccentric waveform models in the context of tests of GR.