Inferring the Stochastic Gravitational-Wave Background from Eccentric Stellar-mass Binary Black Holes with Spaceborne Detectors

TL;DR

This paper uses a Bayesian approach to evaluate the detectability and distinguishing features of the stochastic gravitational-wave background from eccentric stellar-mass binary black holes with spaceborne detectors, considering different formation channels and foreground contamination.

Contribution

It introduces a novel Bayesian framework for assessing the detectability and spectral features of the SGWB from eccentric SBBHs with spaceborne detectors, accounting for multiple formation channels and foreground effects.

Findings

TianQin, LISA, and Taiji can detect SGWBs from SBBHs after 4 years.

Spectral degeneracy exists between the SGWB and a power-law background.

Spectral features from AGN-formed SBBHs can help distinguish the background.

Abstract

The stochastic gravitational-wave background (SGWB) from eccentric stellar-mass binary black holes (SBBHs) holds crucial clues to their origins. For the first time, we employ a Bayesian framework to assess the detectability and distinguishing features of such an SGWB with spaceborne detectors, while accounting for contamination from the Galactic foreground. Our analysis covers eccentric SBBHs from three formation channels: isolated binary evolution, dynamical assembly in globular clusters (GCs), and in active galactic nuclei (AGNs). We find that TianQin, LISA, and Taiji can detect the SGWBs from both isolated and GC-formed SBBHs after 4 years of operation, with the corresponding signal-to-noise ratios of around 10, 60, and 170. However, these backgrounds are spectrally degenerate with a strictly power-law SGWB. Furthermore, highly eccentric SBBHs formed in AGNs yield an SGWB marked by a spectral turnover and sharp decline. While this feature lowers the signal-to-noise ratio by approximately an order of magnitude, it can enable a clear distinction from the strictly power-law background using LISA and Taiji.