The gravitational wave burst signal from core collapse of rotating stars

TL;DR

This study uses detailed simulations to analyze gravitational wave signals from rotating stellar core collapse, confirming a single waveform type and exploring the potential for constraining progenitor properties and instabilities.

Contribution

It provides comprehensive, physics-based gravitational wave templates for core-collapse supernovae and clarifies the waveform morphology and instability conditions.

Findings

Gravitational wave burst is associated with core bounce, not multiple bounces.

Waveform type is consistently identified as type I across varied models.

Postbounce core rotation can lead to dynamical instabilities at low rotation rates.

Abstract

We present results from detailed general relativistic simulations of stellar core collapse to a proto-neutron star, using two different microphysical nonzero-temperature nuclear equations of state as well as an approximate description of deleptonization during the collapse phase. Investigating a wide variety of rotation rates and profiles as well as masses of the progenitor stars and both equations of state, we confirm in this very general setup the recent finding that a generic gravitational wave burst signal is associated with core bounce, already known as type I in the literature. The previously suggested type II (or "multiple-bounce") waveform morphology does not occur. Despite this reduction to a single waveform type, we demonstrate that it is still possible to constrain the progenitor and postbounce rotation based on a combination of the maximum signal amplitude and the peak frequency of the emitted gravitational wave burst. Our models include to sufficient accuracy the currently known necessary physics for the collapse and bounce phase of core-collapse supernovae, yielding accurate and reliable gravitational wave signal templates for gravitational wave data analysis. In addition, we assess the possiblity of nonaxisymmetric instabilities in rotating nascent proto-neutron stars. We find strong evidence that in an iron core-collapse event the postbounce core cannot reach sufficiently rapid rotation to become subject to a classical bar-mode instability. However, many of our postbounce core models exhibit sufficiently rapid and differential rotation to become subject to the recently discovered dynamical instability at low rotation rates.