Broadband extended emission in gravitational waves from core-collapse supernovae

TL;DR

This paper presents a theoretical framework for extended gravitational wave emission from fallback accretion in core-collapse supernovae, highlighting efficiency peaks and spectral characteristics that upcoming detectors could observe.

Contribution

It introduces a general model linking accretion dynamics to gravitational wave signals, including spectral scaling laws and potential observational strategies.

Findings

Maximum GW emission efficiency occurs at hyper-accretion rates.

Characteristic strain amplitude peaks at frequency related to Keplerian angular velocity.

Spectral scaling laws for GW signals are derived and can be tested with future observations.

Abstract

Black holes in core-collapse of massive stars are expected to surge in mass and angular momentum by hyper-accretion immediately following their formation. We here describe a general framework of extended emission in gravitational waves from non-axisymmetric accretion flows from fallback matter of the progenitor envelope. It shows (a) a maximum efficiency in conversion of accretion energy into gravitational waves at hyper-accretion rates exceeding a critical value set by the ratio of the quadrupole mass inhomogeneity and viscosity with (b) a peak characteristic strain amplitude at the frequency $f_b=\Omega_b/\pi$, where $\Omega_b$ is the Keplerian angular velocity at which viscous torques equal angular momentum loss in gravitational radiation, with $h_{char}\propto f^{1/6}$ at $f<f_b$ and $h_{char}\propto f^{-1/6}$ at $f>f_b$. Upcoming gravitational wave observations may probe this scaling by extracting broadband spectra using time-sliced matched filtering with chirp templates, recently developed for identifying turbulence in noisy time series.