Blind spots and biases

The dangers of ignoring eccentricity in gravitational-wave signals from binary black holes

authored by: Divyajyoti, Sumit Kumar, Snehal Tibrewal, Isobel M. Romero-Shaw, Chandra Kant Mishra
Abstract: 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) <0.95 can be up to ≈2.2% compared to ≈0.4% for the baseline population. This results in the loss in signal recovery fraction for up to 6% for the region in parameter space with non-negligible eccentricity (e10>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 e20∼0.1, 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 χp. For injections of e20∼0.1, 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.
Organisation(s): Institute of Gravitation Physics
External Organisation(s): Indian Institute of Technology Madras (IITM)
Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
University of Cambridge
Type: Article
Journal: Physical Review D
Volume: 109
No. of pages: 21
ISSN: 2470-0010
Publication date: 21.02.2024
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Nuclear and High Energy Physics
Electronic version(s): https://doi.org/10.48550/arXiv.2309.16638 (Access: Open)
https://doi.org/10.1103/PhysRevD.109.043037 (Access: Closed)

BibTeX

@article{261fd9ae0a3d49f8bae84fb7ff3c6005,
title = "Blind spots and biases: The dangers of ignoring eccentricity in gravitational-wave signals from binary black holes",
abstract = "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) <0.95 can be up to ≈2.2% compared to ≈0.4% for the baseline population. This results in the loss in signal recovery fraction for up to 6% for the region in parameter space with non-negligible eccentricity (e10>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 e20∼0.1, 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 χp. For injections of e20∼0.1, 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.",
author = "Divyajyoti and Sumit Kumar and Snehal Tibrewal and Romero-Shaw, {Isobel M.} and Mishra, {Chandra Kant}",
note = "Funding Information: I. M. R-S. acknowledges support received from the Herchel Smith Postdoctoral Fellowship Fund. C. K. M. acknowledges the support of SERB{\textquoteright}s Core Research Grant No. CRG/2022/007959. Computations were performed on the powehi workstation in the Department of Physics, IIT Madras, ATLAS cluster at AEI Hannover, and CIT cluster provided by the LIGO Laboratory. The authors are grateful for computational resources provided by the LIGO Laboratory and supported by National Science Foundation Grants No. PHY-0757058 and No. PHY-0823459. We used the following software packages: lals uite , p y cbc , n um p y , m atplotlib , seaborn , jupyter , dynesty , corner . This document has LIGO preprint number LIGO-P2300326 . ",
year = "2024",
month = feb,
day = "21",
doi = "10.48550/arXiv.2309.16638",
language = "English",
volume = "109",
journal = "Physical Review D",
issn = "2470-0010",
publisher = "American Institute of Physics",
number = "4",
}