Controlling Spin and Eccentricity of BBH NR Simulated Waveforms

Two parameters responsible for describing CBC formation, spin-direction and eccentricity, are challenging to reproduce with specific desired values in NR simulations. Implementing a nonlinear variable projection fitting algorithm in NR simulation code SpEC will improve control of these simulation parameters. We show that using this fitting algorithm improves parameter fit quality and convergence time of simulated NR waveforms.