PhD Seminar: Maria Rosselló Sastre, Estudiant del Programa de Doctorat de Física — Modeling the full (l=2, m=0) spherical harmonic: memory effect and ringdown oscillations

The current phenomenological waveform models for binary black hole mergers do not include the (l=2, m=0) spherical harmonic, which is the only mode with l=2 missing in this family of waveform models. In this seminar, I present a fast phenomenological model for the (2,0) mode of the gravitational wave signal emitted by BBH systems in quasi-circular orbits with aligned spins. This mode is of particular interest as it incorporates quasi-normal mode oscillations in the ringdown, in addition to the most significant contribution of the displacement memory. The memory is a nonlinear effect that manifests as a permanent change in the space-time metric, which persists after the gravitational waves have passed. Since the sensitivity of gravitational wave detectors is continuously improving, the demand for more precise waveform models increases, and these models must account for the entirety of gravitational wave behavior to enable a more accurate determination of source properties. Accordingly, the model I present has been implemented as an extension to the IMRPhenomTHM model and can be used for computationally expensive applications such as Bayesian parameter estimation. Finally, I briefly discuss the impact of spin precession in BBH systems on the memory effect and the waveform of this mode.