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Abstract

We continue our study of the binary neutron star parameter space by
investigating the effect of the spin orientation on the dynamics, gravitational
wave emission, and mass ejection during the binary neutron star coalescence. We
simulate seven different configurations using multiple resolutions to allow a
reasonable error assessment. Due to the particular choice of the setups, five
configurations show precession effects, from which two show a precession
(`wobbling') of the orbital plane, while three show a `bobbing' motion, i.e.,
the orbital angular momentum does not precess, while the orbital plane moves
along the orbital angular momentum axis. Considering the ejection of mass, we
find that precessing systems can have an anisotropic mass ejection, which could
lead to a final remnant kick of about $\sim 40 \rm km/s$ for the studied
systems. Furthermore, for the chosen configurations, anti-aligned spins lead to
larger mass ejecta than aligned spins, so that brighter electromagnetic
counterparts could be expected for these configurations. Finally, we compare
our simulations with the precessing, tidal waveform approximant
IMRPhenomPv2_NRTidalv2 and find good agreement between the approximant and our
numerical relativity waveforms with phase differences below 1.2 rad accumulated
over the last $\sim$ 16 gravitational wave cycles.