Gravitational Wave prediction from Galactic binary populations for LISA

Galactic binaries, such as white dwarf binaries and black hole binaries, are expected to be the primary sources of gravitational waves (GWs) detectable by the Laser Interferometer Space Antenna (LISA). Detecting these sources provides an opportunity to unravel critical details about binary star evolution and the broader history of the Milky Way. Using results from the Binary Population and Spectral Synthesis (BPASS) code combined with a Milky Way analogue based on the Feedback in Realistic Environments (FIRE) simulations,we predict 673 white dwarf binaries (WDBs), 4 black hole binaries (BHBs), 86 neutron star binaries, 14 black hole white dwarf binaries, 318 neutron star white dwarf binaries, and black hole neutron star binaries detectable by LISA. We found that the number of predicted systems not dependent on observation simulation method but is highly dependent on the binary population synthesis code used. We also evaluate the signal-to-noise ratios of various binary populations, comparing these predictions with earlier results derived from different binary evolution assumptions, including stable mass transfer and common envelope phases. These comparisons highlight the sensitivity of LISA’s detectable population to the underlying physics of binary evolution, providing an opportunity to refine our theoretical models of stellar remnants. In addition, we conduct an in-depth analysis of the energy spectral density of GWs generated by multiple Galactic binary populations in the mHz frequency range, where LISA is most sensitive. By employing Bayesian modelling approaches, we explore different functional forms of energy spectral densities, such as power-law, broken power-law models, and single-peak models, and address the challenges in accurately characterising GW backgrounds. The complexities of modelling realistic data and the stochastic nature of GW signals emphasise the need for more flexible, adaptive approaches in future data analysis. This thesis provides a comprehensive evaluation of the LISA-detectable compact binary populations, focusing on population predictions and the properties of their GW signals. Our results present key considerations for future GW observations, contributing to a deeper understanding of binary star evolution and the intricate challenges of GW signal modelling.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Physics

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2025

Author dc:creator

• Tang, Petra Nianqi

Advisors dc:contributor.advisor

• Eldridge, Jan
• Meyer, Renate

• Galactic binaries
• gravitational waves
• Laser Interferometer Space Antenna
• BPASS

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/72950

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/72950