Viscous-dynamical ejecta in asymmetric binary neutron star mergers

In 1809.11163 we report about new mass outflow mechanism operating in unequal mass binaries on dynamical timescales and enabled by turbulent viscosity. Viscous-dynamical ejecta are launched during merger due to the thermalization of mass exchange streams between the secondary and the primary neutron star. They are characterized by asymptotic velocities extending up to 0.8 c, and have masses that depend on the efficiency of the viscous mechanism. For values of the viscous parameter expected to arise from magnetohydrodynamics instabilities operating during merger, viscosity is found to enhance the overall mass of the dynamical ejecta by a factor of a few and the mass of the fast tail of the ejecta having asymptotic velocities > 0.6 c by up to four orders of magnitude.

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