Dynamics and gravitational-wave emission of neutron-star merger remnants

Abstract: The coalescence of a neutron-star binary is likely to result in the formation of a neutron-star merger remnant for a large range of binary mass configurations. The massive merger remnant shows strong oscillations, which are excited by the merging process, and emits gravitational waves. Here we discuss possibilities and prospects of inferring unknown stellar properties of neutron stars by the detection of postmerger gravitational-wave emission, which thus leads to constraints of the equation of state of high-density matter. In particular, the dominant oscillation frequency of the postmerger remnant provides tight limits to neutron-star radii. We mention first steps towards a practical implementation of future gravitational-wave searches for the postmerger emission. Moreover, we outline possibilities to estimate the unknown maximum mass of nonrotating neutron stars from such types of measurements. Finally, we review the origin and scientific implications of secondary peaks in the gravitational-wave spectrum of neutron-star mergers and differences in the dynamical behavior of the postmerger remnant depending on the binary configuration. These considerations lead to a unified picture of the post-merger gravitational-wave emission and the post-merger dynamics.