Investigating the effect of in-plane spin directions for precessing binary black hole systems

Morphology of coalescing BBH waveforms are affected by its spins. Waveform models built for inference source parameters have several in-built approximations. In current precessing IMRPhenom and SEOBNR waveform models, systems with the same spin magnitude but varying orientation spins projected on orbital plane effectively mapped to system (bar an overall phase change) asymmetry due precession between $+m$ $-m$ modes is not modelled. this study, we investigate validity these approximations generating numerical relativity (NR) simulations single-spin NR in-plane directions (including superkick configurations) provide estimate SNR at which effect would be measurable. This done computing match using values distinguishability SNR. We also use different magnitudes compare measurability vs. direction. find that direction could measurable SNRs accessible generation detectors, comparable or lower than magnitude. then remove mode-asymmetry content from that, i) removing increases can measured ii) modelling will lead measurement biases. The see mode-asymmetric impacts measurements measurable, therefore conclude effects necessary unbiassed precession.