“Constraining the properties of high-density matter with neutron star merger observations”
The composition and thermodynamic properties of neutron star matter are still elusive. Being composed of high-density matter neutron stars are a natural laboratory to learn more about the fundamental building blocks and interactions of matter. In the first part of the presentation, we will discuss prospects to understand from neutron star mergers whether neutron stars harbor a quark matter core in their centers. We will also address the impact of hyperonic degrees of freedom in mergers. In the second part of the talk we will present a recent analysis, which provides new constraints on the stellar parameters of neutron stars. The reasoning is based on the analysis of the kilonova spectra of GW170817/AT2017gfo and the helium content in the ejecta. The study provides evidence that the merger remnant in GW170817 collapse to a black hole on a relatively short time scale, which implies that the high-density matter equation of state is not particularly stiff.