Three dimensional magnetorotational core-collapse supernova explosions of a 39 solar mass progenitor star

Abstract: We perform three-dimensional simulations of magnetorotational supernovae using a $39\,M_{\odot}$ progenitor star with two different initial magnetic field strengths of $10^{10}$ G and $10^{12}$ G in the core. Both models rapidly undergo shock revival and their explosion energies asymptote within a few hundred milliseconds to values of $\gtrsim 2\times10^{51}$ erg after conservatively correcting for the binding energy of the envelope. Magnetically collimated, non-relativistic jets form in both models, though the jets are subject to non-axisymmetric instabilities. The jets do not appear crucial for driving the explosion, as they only emerge once the shock has already expanded considerably. Our simulations predict moderate neutron star kicks of about $150\, \mathrm{km}\,\mathrm{s}^{-1}$, no spin-kick alignment, and rapid early spin-down that would result in birth periods of about $20\, \mathrm{ms}$, too slow to power an energetic gamma-ray burst jet. More than $0.2\,M_\odot$ of iron-group material are ejected, but we estimate that the mass of ejected $^{56}\mathrm{Ni}$ will be considerably smaller as the bulk of this material is neutron-rich. Explosive burning does not contribute appreciable amounts of $^{56}\mathrm{Ni}$ because the burned material originates from the slightly neutron-rich silicon shell. The iron-group ejecta also show no pronounced bipolar geometry by the end of the simulations. The models thus do not immediately fit the characteristics of observed hypernovae, but may be representative of other transients with moderately high explosion energies. The gravitational-wave emission reaches high frequencies of up to 2000 Hz and amplitudes of over 100 cm. The gravitational-wave emission is detectable out to distances of $\sim4$ Mpc in the planned Cosmic Explorer detector.