Characterizing Spinning Black Hole Binaries in Eccentric Orbits with LISA

TL;DR

This study demonstrates that LISA can accurately measure the orbital eccentricity of merging black hole binaries, aiding understanding of galaxy evolution and merger history, while emphasizing the importance of including eccentricity in waveform models.

Contribution

The paper introduces a comprehensive waveform model including eccentricity, spin precession, and higher harmonics, and assesses LISA's ability to measure eccentricity in black hole binaries.

Findings

Eccentricity can be measured to parts in a thousand for typical LISA sources.

Measurement accuracy of eccentricity is weakly dependent on the eccentricity value.

Including eccentricity in waveform models is crucial to avoid signal loss and parameter bias.

Abstract

The Laser Interferometer Space Antenna (LISA) is designed to detect gravitational wave signals from astrophysical sources, including those from coalescing binary systems of compact objects such as black holes. Colliding galaxies have central black holes that sink to the center of the merged galaxy and begin to orbit one another and emit gravitational waves. Some galaxy evolution models predict that the binary black hole system will enter the LISA band with significant orbital eccentricity, while other models suggest that the orbits will already have circularized. Using a full seventeen parameter waveform model that includes the effects of orbital eccentricity, spin precession and higher harmonics, we investigate how well the source parameters can be inferred from simulated LISA data. Defining the reference eccentricity as the value one year before merger, we find that for typical LISA sources, it will be possible to measure the eccentricity to an accuracy of parts in a thousand. The accuracy with which the eccentricity can be measured depends only very weakly on the eccentricity, making it possible to distinguish circular orbits from those with very small eccentricities. LISA measurements of the orbital eccentricity can help constraints theories of galaxy mergers in the early universe. Failing to account for the eccentricity in the waveform modeling can lead to a loss of signal power and bias the estimation of parameters such as the black hole masses and spins.