A. Arcones, C. Fröhlich, G. Martínez-Pinedo
We study the impact of the late time dynamical evolution of ejecta from
core-collapse supernovae on \nu p-process nucleosynthesis. Our results are
based on hydrodynamical simulations of neutrino wind ejecta. Motivated by
recent two-dimensional wind simulations, we vary the dynamical evolution during
the \nu p-process and show that final abundances strongly depend on the
temperature evolution. When the expansion is very fast, there is not enough
time for antineutrino absorption on protons to produce enough neutrons to
overcome the \beta-decay waiting points and no heavy elements beyond A=64 are
produced. The wind termination shock or reverse shock dramatically reduces the
expansion speed of the ejecta. This extends the period during which matter
remains at relatively high temperatures and is exposed to high neutrino fluxes,
thus allowing for further (p,\gamma) and (n,p) reactions to occur and to
synthesize elements beyond iron. We find that the \nu p-process starts to
efficiently produce heavy elements only when the temperature drops below ~3 GK.
At higher temperatures, due to the low alpha separation energy of 60Zn
(S_{\alpha} = 2.7 MeV) the reaction 59Cu(p,\alpha)56Ni is faster than the
reaction 59Cu(p,\gamma)60Zn. This results in the closed NiCu cycle that we
identify and discuss here for the first time. We also investigate the late
phase of the \nu p-process when the temperatures become too low to maintain
proton captures. Depending on the late neutron density, the evolution to
stability is dominated by \beta decays or by (n,\gamma) reactions. In the
latter case, the matter flow can even reach the neutron-rich side of stability
and the isotopic composition of a given element is then dominated by
neutron-rich isotopes.
View original:
http://arxiv.org/abs/1112.4651
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