Physical Conditions for Synthesis of Sc, Ti, and V in Neutrino-driven Supernovae

TL;DR

This study identifies the specific physical conditions, including neutrino flux and temperature, necessary for synthesizing elements like Sc, Ti, and V in neutrino-driven supernovae, matching observed abundances in metal-poor stars.

Contribution

It provides the first quantitative constraints on the physical conditions required for nucleosynthesis of certain elements in supernovae, emphasizing the importance of multi-dimensional simulations.

Findings

Neutrino exposure of ~10^{35} erg cm^{-2} is needed.

Temperature range for synthesis is 2.0-3.2 GK.

Weak dependence on density and neutrino flux duration.

Abstract

We present the results of simulations of nucleosynthesis in a core-collapse supernova (CCSN) including the neutrino process. Using the Si layer of $13M_\odot$ zero-metal progenitor as the initial composition, we calculate the nucleosynthesis by adopting the temperature, density, neutrino flux, and duration of nucleosynthesis as arbitrary parameters and compare the results with the observed abundances ratio of Sc, Ti, and V in very metal-poor (VMP) stars taken from the Stellar Abundances for Galactic Archaeology (SAGA) database. As a result, for the first time, we identify the quantitative requirements on local physical conditions. To reproduce the abundances ratios in the VMP stars, the explosive nucleosynthesis should take place under the neutrino exposure, which is time integration of neutrino flux, of $\sigma_\nu\sim 10^{35}\,\mathrm{erg~cm^{-2}}$ and temperature of $2.0\,\mathrm{GK}\leq T \leq 3.2\,\mathrm{GK}$. The dependence on the density and each value of the neutrino flux and the duration of nucleosynthesis is weak. We also discuss whether the quantitative requirements are realized during the explosion. Although the requirements are difficult to be realized in the one-dimensional simulations, the non-monotonic thermal evolution shown in recent three-dimensional simulations may satisfy them. Because the evolution is likely caused by turbulent motion stemming from the initial asphericity of the progenitor, it is important to calculate the long-term three-dimensional supernova explosion of multi-dimensional metal-free progenitor models and follow the nucleosynthesis self-consistently.