SN 1987A as a Calorimeter: Neutrino Counts, Explosion Energy and Remnant Binding

SN 1987A remains the only supernova with a detected neutrino burst. Nineteen events across two detectors, at a known distance, provide a calorimetric check on collapse energetics that no other event yet offers. This paper restates that check with explicit numbers and identifies which conclusions the sparse counts do and do not support. Using the calculation described in the Methods, the headline results are: total_events = 19, distance_kpc = 50, Ebind_erg = 2.6e+53, Eexp_erg = 1.1e+51, kinetic_share_pct = 0.421, Enu_inferred_erg = 221000000000000009135653623313246766028494047912394752. The counts support a total radiated energy of a few times 10^53 erg, consistent with a neutron star remnant binding energy, and a kinetic share below one percent. They do not support precise claims about the cooling timescale beyond its order of magnitude, nor do they distinguish among equations of state. Stating those limits plainly protects the strong conclusion, which is calorimetric, from weaker ones that the data cannot carry. This study is simulated and computed from stated assumptions; it is not a measurement. All headline numbers in this abstract appear in the deposited results file and are reproduced by running the deposited code without modification.