Trends in gravitational wave emission in axisymmetric simulations of rotating core-collapse supernovae

TL;DR

This study uses axisymmetric magnetohydrodynamic simulations to analyze how rapid rotation affects gravitational wave signals from core-collapse supernovae, revealing higher frequencies and complex mode interactions.

Contribution

It provides new insights into the impact of strong rotation on GW frequencies and amplitudes, highlighting the limitations of linear mode analysis in rapidly rotating regimes.

Findings

Rotating models produce GWs up to 3 kHz, higher than non-rotating models.

GW frequencies and amplitudes decrease with increasing rotation speed.

No evidence of resonant mode amplification was observed.

Abstract

The quantitative impact of strong rotation on the amplitudes and frequencies of the post-bounce gravitational wave (GW) signal from core-collapse supernovae (CCSNe) is still not fully understood. To study trends in frequencies and amplitudes, and possibly spectacular phenomena like resonant amplification, we perform a series of axisymmetric long-duration magnetohydrodynamic CCSN simulations of a 17 $M_\odot$ progenitor using a finely spaced grid in initial rotation rate from 0.29 rad/s to 3.48 rad/s. We find that these rotating models produce GWs at frequencies of up to 3 kHz, higher than in typical non-rotating models in the literature. The high frequencies arise due to small polar radii of rapidly rotating proto-neutron stars and stabilization by angular momentum gradients at lower latitude. GW frequencies and amplitudes tend to decrease with faster rotation. Different from two complementary simulations without magnetic fields, the magnetohydrodynamic models are characterized by an absence of p-modes above the dominant high-frequency emission band. We find no indication of resonant mode amplification for any rotation rate, although a temporo-spatial and space-frequency analysis reveals some interesting couplings of quadrupolar motions across the proto-neutron star and the gain region. We find that linear mode analysis based on the spherically averaged structure becomes unsuitable in this regime of rapid rotation. More advanced perturbative techniques need to be developed to study the mode structure and mode interaction in the collapse of rapidly rotating massive stars.