A New Gravitational Wave Signature of Low-$T/|W|$ Instability in Rapidly Rotating Stellar Core Collapse

TL;DR

This study uses 3D general relativistic simulations to identify a new gravitational wave signature from low-$T/|W|$ instability during rapidly rotating stellar core collapse, revealing unique non-axisymmetric features.

Contribution

It introduces the first detailed simulation showing gravitational wave signatures of low-$T/|W|$ instability in core-collapse supernovae.

Findings

Detection of strong GW emission from spiral waves in PNS

Identification of unique GW spectrogram features linked to instabilities

Correlation of GW features with PNS contraction and low-$T/|W|$ instability

Abstract

We present results from a full general relativistic three-dimensional hydrodynamics simulation of rapidly rotating core-collapse of a 70 M$_{\odot}$ star with three-flavor spectral neutrino transport. We find a strong gravitational wave (GW) emission that originates from the growth of the one- and two-armed spiral waves extending from the nascent proto-neutron star (PNS). The GW spectrogram shows several unique features that are produced by the non-axisymmetric instabilities. After bounce, the spectrogram first shows a transient quasi-periodic time modulation at $\sim$ 450 Hz. In the second active phase, it again shows the quasi-periodic modulation but with the peak frequency increasing with time, which continues until the final simulation time. From our detailed analysis, such features can be well explained by a combination of the so-called low-$T/|W|$ instability and the PNS core contraction.