Bounds on exotic-particle interactions from SN1987A

The observation of a neutrino pulse from the supernova SN1987A constrains the production of light exotic particles in the proto neutron star. We derive a new bound on the axion decay constant, $f_a$≳${10}^{10}$ GeV. If right-handed (RH) neutrinos exist, the ‘‘RH Fermi constant’’ is $G_{\mathrm{RH}\lesssim {10}^{\mathrm{-}4}{G}_{\mathrm{F}}}$, 2 orders of magnitude below laboratory bounds. The Dirac mass of ${\nu }_{\mu }$ can be constrained below laboratory limits.