Systematic bias on the inspiral-merger-ringdown consistency test due to neglect of orbital eccentricity

TL;DR

Neglecting orbital eccentricity in gravitational waveforms can cause significant systematic biases in the inspiral-merger-ringdown consistency test, potentially leading to false violations of general relativity, especially for third-generation detectors.

Contribution

This paper quantifies the impact of residual orbital eccentricity on the IMR consistency test and highlights the importance of eccentric waveform corrections for accurate GR tests.

Findings

Eccentricity causes bias in final mass and spin estimates at e0 > 0.1 for LIGO.

Bias becomes significant at e0 > 0.015 for Cosmic Explorer.

Eccentricity-induced bias can lead to false GR violations.

Abstract

The inspiral-merger-ringdown (IMR) consistency test checks the consistency of the final mass and final spin of a binary black hole merger remnant, independently inferred via the inspiral and merger-ringdown parts of the waveform. As binaries are expected to be nearly circularized when entering the frequency band of ground-based detectors, tests of general relativity (GR) currently employ quasicircular waveforms. We quantify the effect of residual orbital eccentricity on the IMR consistency test. We find that eccentricity causes a significant systematic bias in the inferred final mass and spin of the remnant black hole at an orbital eccentricity (defined at $10$ Hz) of $e_0 \gtrsim 0.1$ in the LIGO band (for a total binary mass in the range $65$-$200 \,M_{\odot}$). For binary black holes observed by Cosmic Explorer (CE), the systematic bias becomes significant for $e_0 \gtrsim 0.015$ (for $200$-$600 \,M_{\odot}$ systems). This eccentricity-induced bias on the final mass and spin leads to an apparent inconsistency in the IMR consistency test, manifesting as a false violation of GR. Hence, eccentric corrections to waveform models are important for constructing a robust test of GR, especially for third-generation detectors. We also estimate the eccentric corrections to the relationship between the inspiral parameters and the final mass and final spin; they are shown to be quite small.