Origin of coinciding waveforms in the Q2_DD2_e0.1 convergence study

Determine the exact reason why the numerical waveforms for the Q2_DD2_e0.1 black hole–neutron star merger configuration coincide across the investigated resolutions.

Background

The convergence study compares numerical waveforms for the Q2_DD2_e0.1 configuration at resolutions R96, R144, and R192. Although the phase differences remain small, at approximately 0.1 radians or less throughout the inspiral, the authors state that the reason for this coinciding behavior is unknown. Establishing its cause is relevant because the unusually small phase differences may indicate that the simulation has already reached a converged state, rather than reflecting an accidental numerical feature.