Post-Newtonian analysis of approximate helical symmetry in binary black holes

Compact binary systems emitting gravitational radiation have an approximate helical symmetry at future null infinity. We use the post-Newtonian and post-Minkowskian formalisms to compute the flux due to the helical vector field to assess the departure from symmetry. We predict the flux analytically to 4PN order and compare it to NR waveforms from the SXS catalog. The symmetry is satisfied to relative 4PN order and is predicted to break at relative 5PN order from the NR waveforms.