A gravitational wave afterglow in binary neutron star mergers

TL;DR

This paper investigates the gravitational wave signals from rapidly rotating, supermassive neutron stars formed after mergers, analyzing their detectability and implications for neutron star physics.

Contribution

It provides a detailed analysis of gravitational wave emissions from supramassive neutron stars, considering magnetic fields and r-mode instability effects, and assesses their detectability with current and future detectors.

Findings

Gravitational wave signals can be detected up to 20 Mpc with Advanced LIGO.

Detection probability is higher with the Einstein Telescope.

Signal analysis can reveal neutron star equation of state and magnetic field strength.

Abstract

We study in detail the f-mode secular instability for rapidly rotating neutron stars, putting emphasis on supermassive models which do not have a stable nonrotating counterpart. Such neutron stars are thought to be the generic outcome of the merger of two standard mass neutron stars. In addition we take into account the effects of strong magnetic field and r-mode instability, that can drain a substantial amount of angular momentum. We find that the gravitational wave signal emitted by supramassive neutron stars can reach above the Advance LIGO sensitivity at distance of about 20Mpc and the detectability is substantially enhanced for the Einstein Telescope. The event rate will be of the same order as the merging rates, while the analysis of the signal will carry information for the equation of state of the post-merging neutron stars and the strength of the magnetic fields.