[Paper Review] Gravitational-Wave Signatures in Magnetically-driven Supernova Explosions

Tomoya Takiwaki, Kei Kotake|arXiv (Cornell University)|Apr 16, 2010

Astrophysics and Cosmic Phenomena1 references3 citations

TL;DR

This study uses 2D special relativistic MHD simulations to investigate gravitational-wave (GW) signatures in magnetically driven supernova explosions, incorporating realistic equations of state and neutrino cooling. It identifies two distinct GW waveform types—increasing and cancellation—where the increasing type, linked to energetic MHD explosions (~10⁵¹ erg), shows higher detectability with next-generation GW detectors like advanced LIGO and LCGT.

ABSTRACT

Based on a series of two-dimensional, special relativistic magnetohydrodynamic (MHD) simulations of the rotational core-collapse of massive stars, we study the gravitational-wave signatures in the magnetically driven supernova explosion. Pushed by the outcome in recent stellar evolution calculations, we choose to take the precollapse magnetic field less than $10^{12}$ G. By changing the initial field strength and angular momentum distribution parametrically, we compute 12 models. As for the microphysics, a realistic equation of state is employed and the neutrino cooling is taken into account via a multiflavor neutrino leakage scheme. With these computations, we find that the obtained waveforms are categorized into two, which we call as the increasing type or cancellation type. In the increasing type, the total wave amplitudes show almost a monotonic increase after bounce, which is akin to the type IV waveform in the previous work. While in the cancellation type, the total amplitudes after bounce stays almost zero, because the contribution from the magnetic fields cancels with the one from the hydrodynamic counterpart. By utilizing the newly derived formula, these features can be clearly understood with the analysis on the explosion dynamics. The obtained gravitational-wave signals both for the two types are marginally within the detection limits of the currently running detector of the first LIGO and the detection seems more feasible for the detectors in the next generation such as LCGT and the advanced LIGO for a Galactic supernova. Our results suggest that the detection is more promising for the increasing type, which can be obtained in models that produce MHD explosions as energetic as $10^{51}$ erg.

Motivation & Objective

• To investigate gravitational-wave signatures in magnetically driven core-collapse supernovae using realistic microphysics.
• To determine how initial magnetic field strength and angular momentum distribution affect GW emission.
• To assess the detectability of these GW signals with current and next-generation gravitational-wave detectors.
• To classify and understand the physical origin of distinct GW waveform morphologies observed in simulations.

Proposed method

• Performing 2D, special relativistic magnetohydrodynamic (MHD) simulations of rotating massive star core collapse.
• Employing a realistic equation of state and a multiflavor neutrino leakage scheme to model neutrino cooling.
• Systematically varying initial magnetic field strengths below 10¹² G and angular momentum distributions across 12 models.
• Analyzing gravitational-wave emission by decomposing contributions from magnetic and hydrodynamic components.
• Using a newly derived analytical formula to interpret the physical mechanisms behind waveform types.

Experimental results

Research questions

• RQ1 How do varying initial magnetic field strengths and angular momentum distributions influence gravitational-wave emission in magnetically driven supernovae?
• RQ2 What physical mechanisms lead to the emergence of two distinct gravitational-wave waveform types—increasing and cancellation?
• RQ3 To what extent can gravitational-wave signals from such explosions be detected by current and future detectors?
• RQ4 What conditions favor the production of detectable gravitational-wave amplitudes in MHD-driven supernova models?

Key findings

• The gravitational-wave waveforms are categorized into two types: increasing and cancellation, based on post-bounce amplitude evolution.
• In the increasing type, wave amplitudes rise monotonically after bounce, resembling type IV waveforms from prior studies.
• In the cancellation type, wave amplitudes remain near zero due to destructive interference between magnetic and hydrodynamic contributions.
• The increasing type is associated with MHD explosions of energy ~10⁵¹ erg, making it more detectable with next-generation detectors.
• Current LIGO detectors marginally detect such signals, but advanced LIGO and LCGT show significantly improved prospects for Galactic supernovae.
• The physical origin of the two waveform types is clearly explained through analysis of explosion dynamics using a newly derived formula.