Neutrino Energetics of a Tidal Disruption Event: Efficiency With and Without Beaming

A tidal disruption event — a star torn apart by a massive black hole — has been associated with a high-energy neutrino, raising the question of whether the energy budget closes. This paper computes the required efficiency. For an isotropic-equivalent neutrino energy of 5.000e+52 erg and an accretion reservoir of 8.936e+52 erg, from half a solar mass accreted at ten per cent efficiency, isotropic neutrino production demands an efficiency of 0.56 — more than half of all accretion energy emerging as neutrinos, which no interaction model supports. If the emission is beamed into a jet of half-opening angle 0.1 radians, the true neutrino energy falls to 2.500e+50 erg and the required efficiency to 0.0028, a comfortable value. The neutrino association, if real, is therefore evidence for collimated outflow rather than for spherical emission. For scale, radiating the isotropic-equivalent energy at the Eddington luminosity of 3.780e+45 erg per second would take 153 days. The study is computed from stated assumptions, not measured.