Constraints on Dirac Neutrinos from SN 1987A

The Livermore Supernova Explosion Code was used to calculate the effect of a massive Dirac neutrino on neutrino emission from SN 1987A in a fully self-consistent manner. Spin-flip interactions lead to the copious emission of sterile, right-handed neutrinos and cool the core faster than the observed neutrino emission time for Dirac masses exceeding about 3$\,$keV. This limit is relaxed to $7\,$keV if pion emission processes in the core are neglected. These limits are compared with the previous less stringent limits of Burrows et al.