Synergies in analysing binary black hole mergers: Effect of orbital eccentricity, spin-precession, and non-quadrupole modes

Abstract: A gravitational wave (GW) signal carries imprints of the properties of its source. The ability to extract source properties crucially depends on our prior knowledge of the signal morphology. Even though binary black hole (BBH) mergers are the cleanest system to model in general relativity, currently, there are no waveform models which include all physical effects. This thesis focuses on three subdominant effects: orbital eccentricity, spin-precession, and non-quadrupole or higher-order modes (HMs). We study the interplay of these effects on data analysis of GW signals, highlighting the shortcomings and emphasizing the need for more advanced waveforms. For instance, we investigate whether orbital eccentricity and spin-precession can mimic each other and thus caution the GW community towards the biases that may arise due to the neglect of eccentricity and/or spins in the waveform models. Using waveforms with full spin-precession and HMs, we extend the existing spin-induced quadrupole moment (SIQM) test - a null test to distinguish BBH systems from other black hole mimickers - and show that these improved waveforms give significantly better bounds. Additionally, we quantify the parameter space where the effect of HMs is most significant and show the importance of detecting these modes in GW events for future ground-based GW detectors such as Cosmic Explorer and Einstein Telescope.