From inspiral to kilonova

ongoing

"Recent years have seen the blossoming of multi-messenger astrophysics where gravitational waves, photons and neutrinos provide complementary views on cosmic explosions involving some of the Universe’s most enigmatic objects, namely neutron stars and black holes. The first observation of a neutron star merger via both gravitational waves and, days later, an electromagnetic flash called ""kilonova"" enabled huge scientific leaps forward and was therefore celebrated as ""2017 Breakthrough of the Year"". Multi-messenger astrophysics has an enormous potential to solve many longstanding puzzles such as the origin of the heaviest elements or the nature of the densest matter in the Universe, provided that we understand how the different messengers are physically connected. The gravitational wave and electromagnetic emission stages, however, involve vastly different length and time scales and completely different physical processes. Therefore, currently strong assumptions need to be made how both stages are actually physically connected. On the verge of this transformational era of physics, I propose to calculate for the first time the evolution from the inspiral (milliseconds before the merger) to the time after the kilonova (months later) within a common simulation framework. This will become possible via the novel computational methodology that I have recently developed: the world-wide first Lagrangian hydrodynamics code that also consistently solves Einstein's equations. Compared to conventional Numerical Relativity codes, my new development has major advantages in evolving the merger ejecta which finally cause the kilonova. This project will provide for the first time detailed physical structures of neutron star merger remnants and the first one-to-one mapping between the physics of the merger and the gravitational wave, neutrino and electromagnetic signals. This will present a major breakthrough for both the nuclear astrophysics and the multi-messenger communities."