The detection of the gravitational wave event GW170817 from the coalescence of a binary neutron star system, together with its electromagnetic counterparts, has ushered in a new era of multi-messenger astronomy. The event provided additional constraints on neutron star properties and equation of state. Essential to the determination of these source properties are accurate and efficient waveform models. With the advent of more sensitive, next-generation detectors, an increased number of observations with more precise measurements of these systems will be possible, making accurate waveform models all the more crucial. Therefore, this thesis advances waveform modeling in two directions. First, we develop a phenomenological waveform model calibrated to a larger, more diverse set of numerical-relativity simulations and extend it to include higher-order mode corrections. Complementary to traditional waveform modeling techniques, we also propose a novel, data-driven approach towards constructing models by leveraging observational data from next-generation detectors. Second, we investigate gravitational waves from systems beyond conventional binary mergers: we present the first numerical-relativity simulation of a neutron star-sub-solar-mass black hole binary, explore how combined mass and tidal inference helps us classify the sources in low-mass binaries, and perform numerical-relativity simulations of dark matter-admixed binary neutron stars. Together, the results from this thesis demonstrate the development of waveform models that are not only accurate, but also efficient and applicable across broad parameter spaces, while highlighting the need for their continued advancement to fully extract robust astrophysical information from neutron stars and other compact objects.
Adrian Abac (2026) studied this question.