Three-dimensional GRMHD Simulations of Rapidly Rotating Stellar Core-Collapse

TL;DR

This paper presents 3D general relativistic MHD simulations of stellar core collapse, analyzing gravitational wave signatures from magnetorotational mechanisms, highlighting the importance of magnetic fields, rotation, and neutrino emissions.

Contribution

It provides the first detailed 3D GR MHD simulations of core-collapse supernovae focusing on GW signals from magnetorotationally driven outflows, incorporating spectral neutrino transport.

Findings

MHD outflows occur only with specific magnetic and rotational conditions.

Neutrino GW signals dominate matter contributions in amplitude.

Neutrino GW frequencies are below 10 Hz, requiring next-generation detectors.

Abstract

We present results from fully general relativistic (GR), three-dimensional (3D), neutrino-radiation magneto-hydrodynamic (MHD) simulations of stellar core collapse of a 20 M$_\odot$ star with spectral neutrino transport. Our focus is to study the gravitational-wave (GW) signatures from the magnetorotationally (MR)-driven models. By parametrically changing the initial angular velocity and the strength of the magnetic fields in the core, we compute four models. Our results show that the MHD outflows are produced only for models (two out of four), to which magnetic field strengths of 10$^{12}$ G and rotation rates of 1 or 2 rad s$^{-1}$ are initially imposed in the core. Seen from the direction perpendicular to the rotational axis, a characteristic waveform is obtained exhibiting a monotonic time increase in the wave amplitude. As previously identified, this stems from the propagating MHD outflows along the axis. We show that the GW amplitude from anisotropic neutrino emission becomes more than one order-of-magnitude bigger than that from the matter contribution, whereas seen from the rotational axis, both of the two components are in the same order-of-magnitudes. Due to the memory effect, the frequency of the neutrino GW from our full-fledged 3D-MHD models is in the range less than $\sim$10 Hz. Toward the future GW detection for a Galactic core-collapse supernova, if driven by the MR mechanism, the planned next-generation detector as DECIGO is urgently needed to catch the low-frequency signals.