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Spiral-wave wind for the blue kilonova
By Vsevolod Nedora, Sebastiano Bernuzzi, David Radice, Albino Perego, Andrea Endrizzi, Néstor Ortiz
Published in The Astrophysical Journal Letters 886, L30 (Wednesday, November 27, 2019)


The AT2017gfo kilonova (kN) counterpart of the binary neutron star merger event GW170817 was characterized by an early-time bright peak in optical and UV bands. Such blue kN is commonly interpreted as a signature of weak r-process nucleosynthesis in a fast expanding wind whose origin is currently debated. Numerical relativity simulations with microphysical equations of state, approximate neutrino transport, and turbulent viscosity reveal a new hydrodynamics-driven mechanism that can power the blue kN. Spiral density waves in the remnant generate a characteristic wind of mass ~10−2 ${M}_{\odot }$ and velocity ~0.2 c. The ejected material has an electron fraction mostly distributed above 0.25 being partially reprocessed by hydrodynamic shocks in the expanding arms. The combination of dynamical ejecta and spiral-wave wind can account for solar system abundances of r-process elements and early-time observed light curves.