Nucleosynthesis in magnetorotational supernovae: impact of the magnetic field configuration

Abstract

The production of heavy elements is one of the main by-products of the explosive end of massive stars. A long sought goal is finding differentiated patterns in the nucleosynthesis yields, which could permit identifying a number of properties of the explosive core. Among them, the traces of the magnetic field topology are particularly important for extreme supernova explosions, most likely hosted by magnetorotational effects. We investigate the nucleosynthesis of five state-of-the-art magnetohydrodynamic models with fast rotation that have been previously calculated in full 3D and that involve an accurate neutrino transport (M1). One of the models does not contain any magnetic field and synthesizes elements around the iron group, in agreement with other CC-SNe models in literature. All other models host a strong magnetic field of the same intensity, but with different topology. For the first time, we investigate the nucleosynthesis of MR-SNe models with a quadrupolar magnetic field and a 90 degree tilted dipole. We obtain a large variety of ejecta compositions reaching from iron nuclei to nuclei up to the third r-process peak. We assess the robustness of our results by considering the impact of different nuclear physics uncertainties such as different nuclear masses, β−-decays and β−-delayed neutron emission probabilities, neutrino reactions, fission, and a feedback of nuclear energy on the temperature. We find that the qualitative results do not change with different nuclear physics input. The properties of the explosion dynamics and the magnetic field configuration are the dominant factors determining the ejecta composition.

Nucleosynthesis in the Innermost Ejecta of Magnetorotational Supernova Explosions in Three Dimensions

“…Nucleosynthesis calculations based on the 3D neutrino-MHD model simulated with the AENUS-ALCAR code (Obergaulinger & Aloy 2021;Reichert et al 2023) suggest r-process yields of MR CCSNe up to the second peak, i.e., to mass number A ∼ 130. However, the results of Reichert et al (2023Reichert et al ( , 2024) also indicate nontrivial model dependency of the yields. More nucleosynthesis studies using different simulation codes, grid resolutions, and initial model setups are urgently needed to assess the robustness of nucleosynthesis yields from MR CCSNe and quantify uncertainties in yield predictions.…”

“…This suggests that MR explosions without strong collimated jets can be a viable and robust source for weak r-process. Producing heavier elements would require MR explosions with either stronger magnetic fields and specific field configuration (Reichert et al 2024) or other explosion scenarios (e.g., collapsars Siegel et al 2019).…”

“…Current stellar evolutionary simulations thus cannot confidently predict accurate magnetic field strength and multidimensional configuration at the onset of core collapse. This is relevant for MR CCSN nucleosynthesis studies, as Reichert et al (2024) have noticed that the initial magnetic field configuration is an important factor determining the nucleosynthetic conditions of the inner ejecta in MR explosions. Note that recently 3D simulations of short phases of the pre-collapse progenitor evolution with magnetic fields have been performed for the nonrotating case (Varma & Müller 2021) and for a rapidly rotating case (Varma & Müller 2023).…”

“…Spatial resolution is another important numerical aspect, and one needs to balance between the computational costs and the fidelity of the results. For example, Obergaulinger & Aloy (2021) and Reichert et al (2023Reichert et al ( , 2024 adopted a coarse angular resolution of ∼2°. 8 and relatively low radial resolution of 210 zones for several 3D simulations.…”