Post-merger gravitational-wave signal from neutron-star binaries: a new look at an old problem

Understand

The spectral properties of the post-merger gravitational-wave signal from a binary of neutron stars encode a variety of information about the features of the system and of the equation of state describing matter around and above nuclear saturation density.

• Characterising the properties of such a signal is an ``old'' problem, which first emerged when a number of frequencies were shown to be related to the properties of the binary through ``quasi-universal'' relations.
• Here we take a new look at this old problem by computing the properties of the signal in terms of the Weyl scalar $\psi_4$.
• In this way, and using a database of more than 100 simulations, we provide the first evidence for a new instantaneous frequency, $f^{\psi_4}_0$, associated with the instant of quasi time-symmetry in the postmerger dynamics, and which also follows a quasi-universal relation.