Unstable g-modes in Proto-Neutron Stars

TL;DR

This paper investigates whether nonlinear couplings in proto-neutron stars can excite stable g-modes through unstable ones, assessing implications for gravitational wave detection.

Contribution

It provides an analysis of nonlinear mode couplings in proto-neutron stars and evaluates their effectiveness in exciting stable g-modes relevant for gravitational wave signals.

Findings

Nonlinear saturation of unstable modes occurs at low amplitudes.

Coupling between stable and unstable modes is not sufficiently effective.

Excitation of stable g-modes by nonlinear couplings is unlikely to explain observed oscillations.

Abstract

In this article we study the possibility that, due to non-linear couplings, unstable g-modes associated to convective motions excite stable oscillating g-modes. This problem is of particular interest, since gravitational waves emitted by a newly born proto-neutron star pulsating in its stable g-modes would be in the bandwidth of VIRGO and LIGO. Our results indicate that nonlinear saturation of unstable modes occurs at relatively low amplitudes, and therefore, even if there exists a coupling between stable and unstable modes, it does not seem to be sufficiently effective to explain, alone, the excitation of the oscillating g-modes found in hydrodynamical simulations.