On measuring precession in GW190814-like asymmetric compact binaries

Gravitational-wave observations of merging compact binaries hold the key to precision measurements of the objects' masses and spins. General-relativistic precession, caused by spins misaligned with the orbital angular momentum, is considered a crucial tracer for determining the binary's formation history and environment, and it also improves mass estimates -- its measurement is therefore of particular interest. Precession leaves a characteristic signature in the emitted gravitational-wave signal that is even more pronounced in binaries with highly unequal masses. The recent observations of GW190412 and GW190814 have confirmed the existence of such highly asymmetric compact binaries. Here, we perform a systematic study to assess our confidence in robustly measuring precession in GW190814-like high mass ratio binaries and, our ability to measure the mass of the lighter companion in neutron star -- black hole type systems. Using Bayesian model selection we show that precession can be identified robustly in low-mass binaries with moderate mass ratio and mildly precessing spins even in the presence of systematic errors.