The eccentric behavior of inspiralling compact binaries

Nicholas Loutrel, Samuel Liebersbach, Nicolás Yunes, Neil Cornish

Research output: Contribution to journalArticlepeer-review


Even if there is no gauge invariant definition of eccentricity, it has an important impact on the observed gravitational wave signal of such systems, generating power in all possible harmonics of the orbital period. We here clarify the possible discrepancies between different eccentricity parameters used to describe the orbital dynamics of binary systems across different approximations, specifically the post-Newtonian approximation, the selfforce approximation, and numerical relativity. To this end, we highlight disparities between the typically used orbit averaged method of evolving binary systems under radiation reaction, and more direct techniques of solving the two-body problem in post-Newtonian theory. We show, both numerically and analytically, that the orbit averaged method breaks down in the late inspiral, failing to capture a strong secular growth in the Keplerian eccentricity parameter and producing a orbital de-phasing relative to direct integration of the two-body equations of motion. We show that the secular growth and de-phasing affect the observed gravitational wave signal, which could bias how accurately we may recover parameters for systems with signalto-noise ratios ≲100. We further develop a frequency domain post-adiabatic waveform model to capture these effects, and study the precision to which we may estimate parameters with this model through a Fisher information matrix analysis.

Original languageEnglish (US)
Article number025004
JournalClassical and Quantum Gravity
Issue number2
StatePublished - Jan 24 2019
Externally publishedYes


  • eccentric binaries
  • gravitational waves
  • post-Newtonian approximation

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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