New supernova constraints on sterile-neutrino production

We consider the possibility that a light, sterile-neutrino species nu(S) can be produced by nu(e) scattering during the cooling of a proto-neutron star. If we parametrize the sterile-neutrino production cross section by a parameter A as sigma(nu(e)X --> nu(S)X) = A sigma(nu(e) --> nu(e)X), where X is an electron, neutron, or proton, we show that A Is constrained by limits to the conversion of nu(e) to nu(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) less than or similar to A less than or similar to 10(-1).