  We reanalyze $r$-process nucleosynthesis in the neutron-rich ejecta from a
prompt supernova explosion of a low-mass (11 M$_\odot$) progenitor. A pompt
explosion is not yet ruled out as a possibility for low-mass supernova
progenitors. Moreover, there is mounting evidence that a new $r$-process site
may be required. Hence, we assume that a prompt explosion can occur and make a
study of r-process nucleosynthesis in the supernova ejecta. To achieve a prompt
explosion we have performed a general relativistic hydrodynamic simulation of
adiabatic collapse and bounce using a relativistic nuclear-matter equation of
state. The electron fraction $Y_e$ during the collapse was fixed at the
initial-model value. The size of the inner collapsing core was then large
enough to enable a prompt explosion to occur. Adopting the calculated
trajectories of promptly ejected material, we explicitly computed the burst of
neutronization due to electron captures on free protons in the photodissociated
ejecta after the passage of the shock. The thermal and compositional evolution
of the resulting neutron-rich ejecta originating from near the surface of
proto-neutron star was obtained. These were used in nuclear reaction network
calculations to evaluate the products of $r$-process nucleosynthesis. We find
that, unlike earlier studies, the amount of $r$-process material ejected per
supernova is quite consistent with observed galactic $r$-process abundances.
Furthermore, the computed $r$-process abundances are in good agreement with
Solar abundances of $r$-process elements for A$> 100$. This suggests that
prompt supernovae are still a viable $r$-process site. Such events may be
responsible for the abundances of the heaviest $r$-process nuclei.

Astrophysics