It is shown that the neutrino events associated with SN1987A are characterized by the first energetic ($E_{\nu }$∼25 MeV) electron-capture ${\nu }_e$ pulse with quite a high source neutrino flux [$L_{\nu }$,e≃(1–2)×${10}^{53}$ erg], and by the subsequent thermal-pair neutrinos with a modest average energy 〈$E_{\nu }$〉≃7 MeV and also with a reasonable source neutrino flux $L_{\nu }$≃3×${10}^{53}$ erg. Some significant constraints are also derived on particle physics.

• Received 23 March 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.367