Eccentricity or spin precession? Distinguishing subdominant effects in gravitational-wave data by Isobel M. Romero-Shaw et al. on Tuesday 22 November

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.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.07528v2