Misinterpreting Spin Precession as Orbital Eccentricity in Gravitational-Wave Signals

TL;DR

This study investigates the degeneracy between eccentricity and spin-precession in gravitational wave signals, revealing that misinterpretation occurs but is highly localized and depends on signal length and inclination angle.

Contribution

The paper provides a detailed analysis of the degeneracy between eccentricity and spin-precession, highlighting its localized nature and dependence on specific parameters.

Findings

Degeneracy between eccentricity and spin-precession exists but is highly localized.

Misidentification worsens with shorter signals.

Degeneracy sensitivity varies with the source's inclination angle.

Abstract

The increasing scope and breadth of gravitational wave detectors is providing the opportunity to explore new parameters in gravitational-wave astronomy. Eccentricity and spin-precession are two key observables to infer the origin of a gravitational wave (GW) source. The interpretation of GW source parameters can be plagued by degeneracy, such as the well-known degeneracy between mass and spin. As the field has explored new parameters, questions have been raised about possible degeneracies between eccentricity and spin-precession. Although some state-of-the-art models now include these effects individually, models that incorporate spin-precession and eccentricity are only in their infancy. Until models faithfully cover the complete parameter space of compact binary coalescence, our ability to correctly measure the source parameters and infer the formation of the binary is compromised. Here, we present a study of the distinguishability of these two key parameters. Our work finds that there is indeed a degeneracy between eccentricity and spin-precession; however, it is a highly localized effect. We find that the misidentified eccentricity estimates get worse as the signal gets shorter. Additionally, this misidentification is highly sensitive to the inclination angle of the source system. We provide quantifiable estimates of the potency of this degeneracy in addition to identifying some of the regions of parameter space where this degeneracy exists.