EMMI Rapid Reaction Task Force: The physics of neutron star mergers at GSI/FAIR

The observation of gravitational waves (GW) and electromagnetic signals from the neutron star (NS) merger event known as GW170817 has open a new era in Nuclear Astrophysics. The kilonova light curve from this event provided direct evidence of the operation of the r process in mergers. GW waves observations are already putting strong constraints on the high density equation of state. NS mergers connect with all the physics pillars of GSI/FAIR. The properties of matter at high densities and temperatures determine the GW signals from the inspiral and later ringdown phases. They determine the amount of ejected mass during the early dynamical phases and from the accretion disk surrounding the central remnant. Neutrino-matter interactions are fundamental to determine the nucleosynthesis in the ejecta and the electromagnetic signals as already confirmed from the optical and infrared light curves from GW170817. The nuclear properties of exotic neutron-rich nuclei are key for the operation of the r process in the ejecta. The radioactive decay of the freshly synthesized elements drives the light curve whose observational properties depends on the atomic opacities of the freshly synthesized elements. All this aspects need to be combined in numerical relativity simulations that have to be confronted with both gravitational and electromagnetic signals. Furthermore, given the rates constrained by GW170817, we must prepare ourselves to observe from one to fifty neutron star mergers per year from the end of 2018, when the next science run of the LIGO/Virgo detectors begin! The goal of this rapid reaction task force is to foster collaborative efforts between atomic and nuclear physicists, computational astrophysicists, gravitational wave modellers and optical-infrared observers to sharpen and exploit the potential of GSI/FAIR in physics connected to neutron star mergers.