Nucleosynthesis of Mo in neutrino-driven winds

Abstract

Neutrino-driven winds that follow core-collapse supernovae are an exciting astrophysical site for the production of heavy elements. Although hydrodynamical simulations show that the conditions in the wind are not extreme enough for a r-process up to uranium, neutrino-driven winds may be the astrophysical site where lighter heavy elements between Sr an Ag are produced, either by the weak r-process or by the νp-process. However, it is still not clear if the conditions in the wind are slightly neutron-rich or proton-rich. Therefore, we investigate the nucleosynthesis in the wind for neutron-and proton-rich conditions and systematically explore the impact of wind parameters on abundances. Here we focus on molybdenum that has raised attention because several astrophysical scenarios failed to reproduce the solar system (SoS) abundance ratio of 92

Nucleosynthesis in 2D core-collapse supernovae of 11.2 and 17.0 M⊙progenitors: implications for Mo and Ru production

“…It has been shown that different astrophysical sites provide favourable conditions for the production of these isotopes: in (single-degenerate) SNe Ia a γ-process can operate, photodissociating seed nuclei previously produced by the s-process in the companion star [83,84,20]. Neutrino-driven winds in CCSNe have also been studied extensively, with Hoffman et al [22] showing that neutron-rich conditions can lead to the production of the 92,94 Mo isotopes and Bliss & Arcones [71] showing that this is not possible for 96,98 Ru and that the solar ratio between the two Mo isotopes could not be achieved under any conditions. However, the observed solar abundance ratios cannot be achieved in either of the proposed scenarios.…”

“…In the search of the origin of the solar 92,94 Mo and 96,98 Ru abundances, slightly neutron-rich conditions in neutrino-driven winds of CCSNe have been considered before [14,22,[70][71][72]. It is of particular interest to understand the conditions that lead to large abundances for these isotopes.…”

The production of proton-rich isotopes beyond iron: The γ-process in stars

“…The aim is to reproduce the observed abundances by one or more astrophysical scenarios and to determine their contribution to the galactical chemical evolution. Proton-rich neutrino-wind components like the νp process are unable to reproduce the 92,94 Mo solar isotopic ratio [40,41]. Therefore, they do not play a dominant role in the production of the solar inventory of these species.…”

“…[113] proposed that such anomalies are compatible with nucleosynthesis signatures from neutrino-driven winds from CCSNe. This scenario might also explain other anomalies in Mo, e.g., the 95,97 Mo excess compared to solar abundances [113,41]. However, also silicon carbide grains require to condense in C-rich material [94], and isotopic signatures for light elements seem to be compatible with C-rich material from explosive He burning regions [114,88] and not with O-rich material [115].…”

The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics

“…Alternative scenarios to explain neutron-capture signatures in Mo and in all other elements measured in SiC X grains include the neutrino-wind components from the forming neutron star as a source (Hallmann et al 2013, Bliss & Arcones 2014. In this work, we will instead consider the most established scenario to explain the Mo isotopic signature, i.e., where the neutron burst triggered by the 22 Ne(α,n) 25 Mg reaction is the responsible source.…”