Co-production of light p-, s- and r-process isotopes in the high-entropy wind of type II supernovae

We have performed large-scale nucleosynthesis calculations within the high-entropy-wind (HEW) scenario of type II supernovae. The primary aim was to constrain the conditions for the production of the classical "p-only" isotopes of the light trans-Fe elements. We find, however, that for electron fractions in the range 0.458 $\le$ Y$_e$ $\le$ 0.478, sizeable abundances of p-, s- and r-process nuclei between $^{64}$Zn and $^{98}$Ru are coproduced in the HEW at low entropies (S $\le$ 100) by a primary charged-particle process after an $\alpha$-rich freezeout. With the above Y$_e$ -- S correlation, most of the predicted isotopic abundance ratios within a given element (e.g. $^{64}$Zn(p)/$^{70}$Zn(r) or $^{92}$Mo(p)/$^{94}$Mo(p)), as well as of neighboring elements (e.g. $^{70}$Ge(s+p)/$^{74}$Se(p) or $^{74}$Se(p)/$^{78}$Kr(p)) agree with the observed Solar-System ratios. Taking the Mo isotopic chain as a particularly challenging example, we show that our HEW model can account for the production of all 7 stable isotopes, from "p-only" $^{92}$Mo, via "s-only" $^{96}$Mo up to "r-only" $^{100}$Mo. Furthermore, our model is able to reproduce the isotopic composition of Mo in presolar SiC X-grains.}

K. Farouqi, K.-L. Kratz, B. Pfeiffer · 2009