  The p-process nucleosynthesis can explain proton-rich isotopes that are
heavier than iron, which are observed in the Solar System, but discrepancies
still persist and important questions concerning the astrophysical site(s) of
the p-process remain unanswered. We investigate how the p-process operates in
exploding rotating massive stars that have experienced an enhanced s-process
nucleosynthesis during their life through rotational mixing. We computed 25
$M_{\odot}$ stellar models at a metallicity of $Z=10^{-3}$ with different
initial rotation velocities and rates for the uncertain
$^{17}$O($\alpha$,$\gamma$)$^{21}$Ne reaction. The nucleosynthesis calculation,
followed with a network of 737 isotopes, was coupled to stellar evolution, and
the p-process nucleosynthesis was calculated in post-processing during both the
final evolutionary stages and spherical explosions of various energies. In our
models, the p-nuclides are mainly synthesized during the explosion, but not
much during the ultimate hydrostatic burning stages. The p-process yields
mostly depend on the initial number of trans-iron seeds, which in turn depend
on the initial rotation. We found that the impact of rotation on the p-process
is comparable to the impact of rotation on the s-process. From no to fast
rotation, the s-process yields of nuclides with mass number $A<140$ increase by
$3-4$ dex, and so do the p-process yields. Fast rotation with a lower
$^{17}$O($\alpha,\gamma$) rate significantly produces s- and p-nuclides with
$A\geq140$. Our results suggest that the contribution of core-collapse
supernovae from massive stars to the solar (and Galactic) p-nuclei has been
underestimated in the past, and more specifically, that the contribution from
massive stars with sub-solar metallicities may even dominate. A more detailed
study including stellar models with a wide range of masses and metallicities
remains to be performed.
