Binary Neutron Star Mergers with Spinning Components and Second-Moment Neutrino Transport

We report on merger simulations of magnetized, highly spinning (χ = ± 0.43) neutron stars featuring second-moment neutrino transport. Via spin-orbit coupling, stars with spins aligned with the orbital angular momentum experience a slower plunge prior to merger, where extended tidal interactions eject a cooler, flatter, neutron-rich postmerger accretion disk compared to a nonspinning binary. This process steers debris away from polar regions that would otherwise choke a relativistic jet, leading to higher radial velocities, EM luminosities, and magnetizations driving a neutron-poor polar outflow. However, terminal Lorentz factors are still about ~10 in the aligned-spin outflow despite the ideal conditions induced by our initial data and neutrino cooling, casting doubt on the possibility of magnetar progenitors generating gamma-ray bursts following BNS mergers. We observe opposite effects from the more violent plunge seen in anti-aligned spin-orbit coupled binaries, which lead to hotter, more isotropic ejecta. The broad range of thermodynamic conditions and disk structures seen in different spin cases will further lead to different late-time ejecta profiles, nucleosynthesis yields, and kilonova signals.