Eccentricity or spin precession? Distinguishing subdominant effects in gravitational-wave data

Romero-Shaw, Isobel, Gerosa, Davide and Loutrel, Nicholas 2023. Eccentricity or spin precession? Distinguishing subdominant effects in gravitational-wave data. Monthly Notices of the Royal Astronomical Society 519 (4) , pp. 5352-5357. 10.1093/mnras/stad031

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Abstract

Eccentricity and spin precession are key observables in gravitational-wave astronomy, encoding precious information about the astrophysical formation of compact binaries together with fine details of the relativistic two-body problem. However, the two effects can mimic each other in the emitted signals, raising issues around their distinguishability. Since inferring the existence of both eccentricity and spin precession simultaneously is – at present – not possible, current state-of-the-art analyses assume that either one of the effects may be present in the data. In such a setup, what are the conditions required for a confident identification of either effect? We present simulated parameter inference studies in realistic LIGO/Virgo noise, studying events consistent with either spin precessing or eccentric binary black hole coalescences and recovering under the assumption that either of the two effects may be at play. We quantify how the distinguishability of eccentricity and spin precession increases with the number of visible orbital cycles, confirming that the signal must be sufficiently long for the two effects to be separable. The threshold depends on the injected source, with inclination, eccentricity, and effective spin playing crucial roles. In particular, for injections similar to GW190521, we find that it is impossible to confidently distinguish eccentricity from spin precession.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Physics and Astronomy
Publisher:	Oxford University Press
ISSN:	1365-2966
Date of First Compliant Deposit:	19 February 2026
Date of Acceptance:	4 January 2023
Last Modified:	19 Feb 2026 12:00
URI:	https://orca.cardiff.ac.uk/id/eprint/185055

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