ASTROPHYSICS

This ongoing project aims at investigating the long-term evolution of a merging binary system of two neutron stars. The investigation conducted within this project is well aligned with the past research conducted by the Relastro group in Frankfurt and is motivated by the gravitational-wave detection GW170817 and its electromagnetic counterpart, the
so-called kilonova. This kilonova signal is produced by the nuclear processes within the dense and neutron rich mass that is ejected during the merger. Since a lot of mass is ejected during the longterm postmerger evolution, it is crucial to investigate this part via state-of-the-art simulations in order to fully understand the observation.

Two major events are responsible for what is considered the “golden age” of relativistic astrophysics. One is the detection of gravitational waves from merging neutron stars heralding the beginning of the multimessenger age. The other is the effort of the Event Horizon Telescope collaboration culminating in the first image of a black hole. Both events have been aided by simulations that require HPC. With this project, several studies could be conducted well alligned with these type of simulations expanding our knowledge about these important astrophysical events.

The age of multi-messenger gravitational wave astronomy has arrived. The simultaneous detection of gravitational and electromagnetic waves from merging neutron stars has illustrated the importance of having high resolution numerical relativity simulations, performed on SuperMUC, available to disentangle the complex interplay of nuclear physics, neutrino physics, and strong field gravity. Using these simulations, it is possible to study matter at densities unreachable with terrestrial experiments and determine the origin of the heavy elements in the universe.

Leveraging the HPC infrastructure of LRZ, researchers at the Goethe University in Frankfurt/Main employ a series of in-house developed cutting-edge numerical methods to simulate in full general relativity the inspiral, merger, and collapse of neutron stars. The computationally intense, fully parallel simulations incorporate relativistic hydrodynamics, nuclear finite-temperature equations of state, and an approximate treatment of neutrino emission and absorption. The results, obtained by measuring gravitational waves, can provide important information on the properties of matter at nuclear densities.