Effects of Rotation on Stochasticity of Gravitational Waves in Nonlinear Phase of Core-Collapse Supernovae

TL;DR

This study uses 3D simulations to explore how rotation influences the stochastic nature of gravitational waves emitted during core-collapse supernovae, revealing that rotation causes more predictable GW signals aligned with the spin axis.

Contribution

It demonstrates that rotation reduces the stochasticity of neutrino-driven gravitational waveforms by aligning emission along the spin axis, a novel insight into GW emission mechanisms in supernovae.

Findings

Rotation leads to more deterministic GW signals.

Neutrino emission aligns with the spin axis in rotating models.

Detection prospects are promising with future space interferometers.

Abstract

By performing three-dimensional (3D) simulations that demonstrate the neutrino-driven core-collapse supernovae aided by the standing accretion shock instability (SASI), we study how the spiral modes of the SASI can have impacts on the properties of the gravitational-wave (GW) emission. To see the effects of rotation in the non-linear postbounce phase, we give a uniform rotation on the flow advecting from the outer boundary of the iron core, whose specific angular momentum is assumed to agree with recent stellar evolution models. We compute fifteen 3D models in which the initial angular momentum as well as the input neutrino luminosities from the protoneutron star are changed in a systematic manner. By performing a ray-tracing analysis, we accurately estimate the GW amplitudes generated by anisotropic neutrino emission. Our results show that the gravitational waveforms from neutrinos in models that include rotation exhibit a common feature otherwise they vary much more stochastically in the absence of rotation. The breaking of the stochasticity stems from the excess of the neutrino emission parallel to the spin axis. This is because the compression of matter is more enhanced in the vicinity of the equatorial plane due to the growth of the spiral SASI modes, leading to the formation of spiral flows circulating around the spin axis with higher temperatures. We point out that a recently proposed future space interferometers like Fabry-Perot type DECIGO would permit detection of these signals for a Galactic supernova.