Blind spots and biases: The dangers of ignoring eccentricity in gravitational-wave signals from binary black holes

Most gravitational wave (GW) events observed so far by the LIGO and Virgo detectors are consistent with mergers of binary black holes (BBHs) on quasicircular orbits. However, some events, such as GW190521, are also consistent with having nonzero orbital eccentricity at detection, which can indicate that the binary formed via dynamical interactions. Active GW search pipelines employing quasicircular waveform templates are inefficient for detecting eccentric mergers. Additionally, analysis of GW signals from eccentric BBH with waveform models neglecting eccentricity can lead to biases in the recovered parameters. Here, we explore the detectability and characterization of eccentric signals when searches and analyses rely on quasicircular waveform models. We find that for a reference eccentric population, the fraction of events having fitting factor (FF) 0. 01) and high mass ratio (q>3). We perform parameter estimation (PE) for nonspinning and aligned-spin eccentric injections of GWs from binaries of total mass M=35M_, based on numerical relativity simulations and an effective one-body (EOB) based inspiral merger-ringdown model (teobresums), and recover them using both quasicircular and eccentric waveform models. For e₂₀0. 1, analyses using quasicircular waveform models are unable to recover the injected chirp mass within the 90% credible interval. Further, for these low-mass injections, spin-induced precession does not mimic eccentricity, with PE correctly ruling out high values of effective precession parameter ₏. For injections of e₂₀0. 1, PE conducted with an inspiral-only eccentric waveform model correctly characterizes the injected signal to within 90% confidence, and recovers the injected eccentricities, suggesting that such models are sufficient for characterization of low-mass eccentric BBH.