Detectability of eccentric binary black holes with matched filtering and unmodeled pipelines during the third observing run of LIGO-Virgo-KAGRA

Abstract

Detecting binary black hole (BBH) mergers with quantifiable orbital eccentricity would confirm the existence of a dynamical formation channel for these binaries. The current state-of-the-art gravitational wave searches of LIGO-Virgo-KAGRA strain data focus more on quasicircular mergers due to increased dimensionality and lack of efficient eccentric waveform models. In this work, we compare the sensitivities of two search pipelines, the matched filter-based PyCBC and the unmodeled coherent wave burst (cWB) algorithms toward the spinning eccentric BBH mergers, using a multipolar nonprecessing-spin eccentric signal model, SEOBNRv4EHM. Our findings show that neglecting eccentricity leads to missed opportunities for detecting eccentric BBH mergers, with PyCBC exhibiting a 10%-20% sensitivity loss for eccentricities exceeding 0.2 defined at 10 Hz. In contrast, cWB is resilient, with a 10% sensitivity increase for heavier (M≥30M⊙) eccentric BBH mergers, but is significantly less sensitive than PyCBC for lighter BBH mergers. Our fitting factor study confirmed that neglecting eccentricity biases the estimation of chirp mass, mass ratio, and effective spin parameter, skewing our understanding of astrophysical BBH populations, fundamental physics, and precision cosmology. Our results demonstrate that the current search pipelines are not sufficiently sensitive to eccentric BBH mergers, necessitating the development of a dedicated matched-filter search for these binaries. Whereas, burst searches should be optimized to detect lower chirp mass BBH mergers, as eccentricity does not affect their search sensitivity significantly.