SN1987A supernova: a black-hole precursor?

Abstract

The 11 + 8 neutrino events observed at Kamiokande¹ and IMB² detectors have been analysed by several authors^1–12. The inferred total neutrino luminosity W_v and its distribution among the various neutrino species, vary between the different analyses depending on the events included in the analysis, the parameterization of the neutrino spectra, the role played by v_e–oxygen scattering, the distance of the Large Magellanic Cloud (LMC) and other aspects. Most authors find high total neutrino energy, in the range W_v = 3–6.7×10⁵³ erg, and a large flux of prompt neutronization neutrinos ${\text{Φ}}_{V_{\text{e}}}^{\text{prompt}}$≈10¹⁰cm⁻². The Kamiokande collaboration¹ has quoted a value of $W_{{\stackrel{\_}{v}}_{\text{e}}}$ = 8×10⁵² erg for the total v̄_e energy. This value is subject to uncertainties in the distance to the LMC, low statistics and other experimental and theoretical factors. From this value we have deduced⁸ that W_v≈6.7×10⁵³ erg which implies a gravitational energy release ≳0.37 M_⊙c². This value is too high for a binding energy of a standard, 1.4 M_⊙, neutron star which means that a massive M≳2 M_⊙ neutron star or a black hole form. In the following we focus on lepton number conservation and the ensuing limitation on ${\text{Φ}}_{V_{\text{e}}}^{\text{prompt}}$. We show that an identification of the first two events in the Kamiokande data as v_e prompt events requires a mass, M≳6 M_⊙, which implies a black-hole formation. This is also consistent with the probable identification of the progenitor¹³ as a B3I supergiant of ∼25M_⊙.