Relativistic Simulations of Neutron Star and Strange Star Mergers

Abstract

Compact stars made of strange matter, though still a hypothetical energetic ground state of matter, may be an alternative to neutron stars in accordance with the observed properties of the known compact stars. Binary systems of these so-called strange stars or of ordinary neutron stars do not exist infinitely long, but their orbits shrink due to gravitational-wave emission so that after some 100 million years of evolution the two compact objects merge. We investigate in our project how observations of such merger events, primarily by upcoming gravitational-wave experiments that will have the capability to detect such sources out to the Virgo galaxy cluster in 20 Mpc distance, could help to decide on the existence of strange matter stars. By performing three-dimensional relativistic hydrodynamical simulations on the HLRB II SGI Altix 4700 machine at the Leibniz-Rechenzentrum we identify fundamental differences between mergers of neutron stars and strange stars. The analysis of the simulated models focuses on observable signatures of the collision events, in particular on gravitational-wave measurements and the detection of strange matter clumps (“strangelets”) ejected during the merging and making a contribution to the cosmic ray flux. The results suggest that once the experiments reach the required sensitivity, a decision on the existence of strange stars may become possible.