Spin precession and nutation of isolated stellar-mass black-hole binaries*

The spins of binary black holes (BBHs) that originate from isolated binary stars are determined by the interplay of various phenomena. The possibility for these BBHs to experience spin precession, which modulates the gravitational waves (GWs) they emit, also depends on these phenomena. If isolated BBHs have negligible spins, then spin precession would be greatly suppressed. In previous work, we identified regions of the parameter space that may produce BBHs with large misalignments from natal kicks and high spin magnitudes from three mechanisms - tides, accretion, or inheritance via minimal core-envelope coupling. Here, we explore the precession and nutation of such BBHs. We find that precession is possible from natal kicks and that nutation depends on the spin-up mechanisms. Small spins from maximal core-envelope coupling ensure that BBHs only exhibit precession, except when tides synchronize both spins of the binary to allow for nutation. While accretion can produce high spin, it does not allow for nutation as it does not occur for both binary components in any of our pathways. Generally, nutation is difficult to achieve without minimal core-envelope coupling, implying that a measurement of nutation from GWs might suggest isolated origin with minimal core-envelope coupling.