By using SN1987A as a ‘‘source’’ of neutrinos with energy app10 MeV we place limits on the couplings of neutrinos with cosmic background particles. Specifically, we find that the Majoron–electron-neutrino coupling must be less than about ${10}^{\mathrm{-}3}$; if neutrinos couple to a massless vector particle, its dimensionless coupling must be less than about ${10}^{\mathrm{-}3}$; and if neutrinos couple with strength g to a massive boson of mass M, then g/M must be less than 12 ${\mathrm{MeV}}^{\mathrm{-}1}$.

• Received 13 July 1987

DOI:https://doi.org/10.1103/PhysRevD.36.2895