New Supernova Constraints on Sterile-Neutrino Production

We consider the possibility that a light, sterile-neutrino species νS can be produced by νₑ scattering during the cooling of a proto-neutron star. If we parametrize the sterile-neutrino production cross section by a parameter A as ${σ}({{ν}}ₑX{→}{{ν}}SX){{0ex}{0ex}}={{0ex}{0ex}}A{σ}({{ν}}ₑX{→}{{ν}}ₑX)$, where $X$ is an electron, neutron, or proton, we show that $A$ is constrained by limits to the conversion of ${{ν}}ₑ$ to ${{ν}}S$ in the region between the sterile-neutrino trapping region and the electron-neutrino trapping region. This consideration excludes values of $A$ in the range ${10}^{{-}4}{}A{}{10}^{{-}1}$.