Binary neutron star mergers: realistic spins and quasiuniversal relations

Tim Dietrich, Universität Jena

We present nonlinear general relativistic dynamical evolutions for constraint satisfying initial data of spinning neutron star binaries. By comparison with a binary black hole configuration one can estimate the different tidal and spin contributions. The phase evolution during the orbital motion is significantly affected by spin-orbit interactions, leading to delayed or early mergers. Furthermore, a frequency shift in the main emission mode of the hyper-massive neutron star can be observed.
Additionally, we show that quasiuniversal relations between the mass-rescaled gravitational wave frequency and the binding energy at the moment of merger, and certain dimensionless binary tidal coupling constants can be found in fully-general relativistic simulations. Such relations are predicted by the effective-one-body model and expected to characterize neutron star mergers dynamics. In the context of gravitational wave astronomy, these universal relations may be used to constrain the neutron star equation of state using waveforms that model the merger accurately.