Nucleosynthesis in neutrino-driven winds in hypernovae

TL;DR

This paper explores nucleosynthesis in neutrino-driven winds from a proto-neutron star formed during hypernovae, revealing conditions for r-process and νp-process element production with implications for observed stellar abundances.

Contribution

It provides the first detailed wind solutions from a hypernova-related proto-neutron star, analyzing conditions for heavy element synthesis in neutron-rich and proton-rich environments.

Findings

r-process occurs in neutron-rich winds matching some metal-poor star abundances

νp-process produces A>100 nuclides in proton-rich winds

neutrino luminosities influence neutron/proton richness of the wind

Abstract

We investigate the nucleosynthesis in the neutrino-driven winds blown off from a $3M_\odot$ massive proto-neutron star (mPNS) temporarily formed during the collapse of a $100M_\odot$ star. Such mPNSs would be formed in hypernovae. We construct steady and spherically symmetric wind solutions. We set large neutrino luminosities of $\sim 10^{53}\ {\rm erg\ s^{-1}}$ and average energies of electron neutrinos and antineutrinos in the ranges of $\epsilon_{\nu_e}=9-16\ {\rm MeV}$ and $\epsilon_{\bar{\nu}_e}=11-18\ {\rm MeV}$ based on a recent numerical relativity simulation. The wind solutions indicate much shorter temperature-decrease timescale than that of the winds from ordinary PNSs and, depending on $\epsilon_\nu$, the winds can be both neutron-rich and proton-rich. In the neutron-rich wind, the $r$-process occurs and the abundance distribution of a fiducial wind model of the mPNS gives an approximate agreement with the abundance pattern of metal-poor weak $r$ star HD~122563, although the third-peak elements are produced only when the $\bar{\nu}_e$ energy is much larger than the $\nu_e$ energy. In the proton-rich wind, the strong $\nu p$-process occurs and $A>100$ nuclides are synthesized. The synthesized nuclei can be neutron-rich in some cases because the large neutrino luminosity of the mPNS supplies a sufficient amount of neutrons.