  The method of the statistical sample moments was used for the analysis of
neutrino events from SN1987A burst in Cherenkov detectors. In particular the
coefficients of correlation $Q(E,t)$ between the energies $E$ of electron
antineutrinos $\bar \nu_e$ emitted by star and the ejection instants $t$ of
$\bar \nu_e$ for neutrino events recorded by Cherenkov water detectors of KII
and IMB collaborations were calculated. $Q(E,t)$ values depend on the assumed
mass of $\bar \nu_e$. Modern model of the gravitational stellar core collapse
with an accretion phase predicts the low level of such correlation $<Q(E,t)>$
averaged with respect to neutrino burst. On condition that empirical $Q(E,t)$
values equal the theoretical model quantities $<Q(E,t)>$ one can obtain
$22\pm10 eV/c^{2}$ as an estimate of the nonzero $\bar \nu_e$ mass. The error
of this estimate implies that $\bar \nu_e$ mass less than $2 eV/c^2$ is
unlikely. The laboratry data of the tritium $\beta$-decay agree adequately with
the presented astrophysical estimate provided that the anomalous structure near
the end point of $\beta$-spectrum is taken into account.
