  We return to interpreting the historical SN~1987A neutrino data from a modern
perspective. To this end, we construct a suite of spherically symmetric
supernova models with the Prometheus-Vertex code, using four different
equations of state and five choices of final baryonic neutron-star (NS) mass in
the 1.36-1.93 M$_\odot$ range. Our models include muons and proto-neutron star
(PNS) convection by a mixing-length approximation. The time-integrated signals
of our 1.44 M$_\odot$ models agree reasonably well with the combined data of
the four relevant experiments, IMB, Kam-II, BUST, and LSD, but the
high-threshold IMB detector alone favors a NS mass of 1.7-1.8 M$_\odot$,
whereas Kam-II alone prefers a mass around 1.4 M$_\odot$. The cumulative energy
distributions in these two detectors are well matched by models for such NS
masses, and the previous tension between predicted mean neutrino energies and
the combined measurements is gone, with and without flavor swap. Generally, our
predicted signals do not strongly depend on assumptions about flavor mixing,
because the PNS flux spectra depend only weakly on antineutrino flavor. While
our models show compatibility with the events detected during the first
seconds, PNS convection and nucleon correlations in the neutrino opacities lead
to short PNS cooling times of 5-9 s, in conflict with the late event bunches in
Kam-II and BUST after 8-9 s, which are also difficult to explain by background.
Speculative interpretations include the onset of fallback of transiently
ejected material onto the NS, a late phase transition in the nuclear medium,
e.g., from hadronic to quark matter, or other effects that add to the standard
PNS cooling emission and either stretch the signal or provide a late source of
energy. More research, including systematic 3D simulations, is needed to assess
these open issues.
