Neutrino-Induced Nucleosynthesis and the Site of therProcess

If the $r$ process occurs deep within a type II supernova, probably the most popular of the proposed sites, abundances of $r$-process elements may be altered by the intense neutrino flux. We point out that the effects would be especially pronounced for eight isotopes that can be efficiently synthesized by the neutrino reactions following $r$-process freeze-out. We show that the observed abundances of these isotopes are entirely consistent with neutrino-induced nucleosynthesis, strongly arguing for a supernova $r$-process site. The deduced neutrino fluences place stringent constraints on the freeze-out radius and dynamic time scale of the $r$ process.