Spectral properties of gravitational waves from neutron star merger remnants

We present a new analytic model describing gravitational wave emission in the post-merger phase of binary neutron star mergers. The model is determined by a number of physical parameters that are related to various oscillation modes, combination tones or non-linear features. The time evolution of the main post-merger frequency is incorporated. The model achieves high fitting factors for a sequence of equal-mass simulations of varying mass. All parameters of the model correlate with the total binary mass. For high binary masses, we identify new spectral features originating from the non-linear coupling between the quasi-radial oscillation and an antipodal tidal deformation of the remnant, the inclusion of which enhances the corresponding fitting factors. We find that subdominant frequency components are crucial for the construction of faithful gravitational wave templates. Because of the high fitting factors our model is particularly suitable for searches with upgraded detectors of the current generation (aLIGO+, aVirgo+) or future detectors. We find a quasi-universal relation for the proximity of a binary configuration to black-hole formation. We then develop a method for determining the threshold mass for prompt black-hole formation and the maximum mass of non-rotating neutron stars. This procedure relies on one precise measurement of the inspiral and post-merger phase.