The flux of electron antineutrinos from supernova SN1987A data

Abstract

By adopting a state-of-the-art parameterized model of electron antineutrino emission, we have made some steps forward in the analysis of the thermodynamical properties and temporal structure of neutrino emission from core collapse SN1987A. Our analysis, unlike similar previous ones, takes into account the times, energies and angles of arrival of the detected events in a reliable framework which includes a finite ramp in the initial stage of the neutrino emission. The existence of the accretion phase is confirmed with a confidence level of about 99%. Our fit shows that the mass of neutrons involved in reactions with hot positrons, leading to the emission of electron antineutrinos during accretion, is a small fraction of the mass of the outer core. We determine the parameters of the cooling emission and discuss its duration, that compares well with theoretical expectations. We estimate the delay times between the first neutrino and the first event in the detectors. The goodness of fit checks, performed on the temporal, energy and angular distributions, show that the flux resulting from the best-fit analysis is compatible with the observed data.