Saturation of the f-mode instability in neutron stars

Abstract

As a result of the Chandrasekhar-Friedman-Schutz (CFS) instability, the f -mode (fundamental oscillation) in a newborn neutron star can grow and produce a significant gravitational wave signal. This star is usually the result of a core-collapse supernova explosion, but may also be the aftermath of a binary neutron star merger, where a rapidly rotating, supramassive configuration is formed, before its collapse to a black hole. The gravitational wave signal could possibly be detected by the next generation gravitationalwave detectors and, thus, provide useful information about the neutron star equation of state. However, nonlinear mode coupling suppresses the growth of the f -mode and saturates it. The saturation amplitude determines the strength of the signal, as well as the evolutionary route of the star inside the so-called instability window.