Implications of the LISA stochastic signal from eccentric stellar mass black hole binaries in vacuum
Year: 2026
Type: article
Abstract: Astrophysical formation channels of stellar-mass binary black holes (sBBHs) can induce significant orbital eccentricities in their early inspiral. We analyze the implications on the stochastic gravitational-wave background (SGWB) from unresolved sBBHs, which can be detected with the Laser Interferometer Space Antenna (LISA). We develop an improved SGWB model for the case of an idealized Dirac-delta eccentricity distribution, and extend it to the more astrophysical case of a thermal distribution. Using a fully Bayesian framework, we find that, if all binaries have a high initial eccentricity e 0 ≳ 0.9 at an orbital frequency of f orb = 10 − 4 Hz , the resulting SGWB can be robustly distinguished from a background of quasicircular sBBHs. For a thermal eccentricity distribution, the SGWB is consistent with a circular model when binaries form at f orb = 10 − 5 Hz , but leads to significant systematic biases if formation occurs at f orb = 10 − 4 Hz . We also show that, when eccentricity is properly accounted for, environmental effects such as dynamical friction can be distinguished from vacuum evolution, but only for sufficiently dense environments with gas densities ρ ≳ 10 − 7 g cm − 3 . Finally, we show that a LISA detection of the sBBH SGWB would place an upper bound on the maximum eccentricity of the sBBH population in the band of ground-based detectors, with direct implications for template modeling and data analysis. Our results highlight the importance of incorporating eccentricity in SGWB modeling to enable accurate astrophysical interpretation of LISA observations.
DOI: 10.1103/pbdv-rf6j
Institutions: University of Science and Technology of China, Scuola Internazionale Superiore di Studi Avanzati, Purple Mountain Observatory, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Institute for Fundamental Physics of the Universe, Max Planck Institute for Gravitational Physics, Istituto Nazionale di Fisica Nucleare, Sezione di Milano Bicocca, University of Milano-Bicocca, University of Birmingham
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7160632383