r-Process nucleosynthesis from three-dimensional jet-driven core-collapse supernovae with magnetic misalignments

Abstract

We investigate r-process nucleosynthesis in three-dimensional general relativistic magnetohydrodynamic simulations of jet-driven supernovae resulting from rapidly rotating, strongly magnetized core-collapse. We explore the effect of misaligning the pre-collapse magnetic field with respect to the rotation axis by performing four simulations: one aligned model and models with 15°, 30°, and 45°misalignments. The simulations we present employ a microphysical finite-temperature equation of state and a leakage scheme that captures the overall energetics and lepton number exchange due to post-bounce neutrino emission and absorption. We track the thermodynamic properties of the ejected material with Lagrangian tracer particles and analyse its composition with the nuclear reaction network S N . By using different neutrino luminosities in post-processing the tracer data with S N , we constrain the impact of uncertainties in neutrino luminosities. We find that, for the aligned model considered here, the use of an approximate leakage scheme results in neutrino luminosity uncertainties corresponding to a factor of 100-1000 uncertainty in the abundance of third peak r-process elements. Our results show that for misalignments of 30°or less, r-process elements are robustly produced as long as neutrino luminosities are reasonably low ( 5 × 10 52 erg s −1 ). For a more extreme misalignment of 45°, we find the production of r-process elements beyond the second peak significantly reduced. We conclude that robust r-process nucleosynthesis in magnetorotational supernovae requires a progenitor stellar core with a large poloidal magnetic field component that is at least moderately (within ∼ 30°) aligned with the rotation axis.

Kilonovae

“…The latter can disrupt and slow the expansion rate of jet-like structures (Mösta et al. 2014), rendering the creation of the heaviest (third abundance-peak) r -process elements challenging to obtain (Halevi and Mösta 2018).…”

r-process Nucleosynthesis from Three-dimensional Magnetorotational Core-collapse Supernovae

“…Magnetorotational core-collapse supernovae (Bisnovatyi-Kogan 1970;LeBlanc & Wilson 1970;Meier et al 1976;Wheeler et al 2002;Mösta et al 2014a) are promising candidate sites for r-process nucleosynthesis (Winteler et al 2012;Nishimura et al 2015Nishimura et al , 2017bHalevi & Mösta 2018). They are also proposed to be the engines driving hyperenergetic supernovae from stripped-envelope progenitors, classified as Type Ic-bl (H/He deficient, broad spectral lines).…”

The Physics of Kilonovae

“…Likewise, it is difficult to explain enrichment in ultrafaint dwarf galaxies [108] with mergers, given that the velocities pre-merger binaries acquire when their component stars go supernova generally exceed the low escape velocities of these lowmass galaxies [109]. A variety of alternative r-process sites have been proposed [110][111][112][113]; however, a complete census of merging systems will clarify rates and ejected mass, and illuminate the role of mergers in burning the heaviest elements.…”