The recently discovered high-energy transient Swift $J164449.3+573451$ (Sw $J1644+57$) is thought to arise from the tidal disruption of a passing star by a dormant massive black hole. Modeling of the broadband emission suggests the presence of a powerful relativistic jet, which contributes dominantly to the observed x-ray emission. Here we suggest that protons can be accelerated to ultrahigh energies by internal shocks occurring in the jets, but their flux is insufficient to account for the observed flux of ultrahigh-energy cosmic rays. High-energy protons can produce $\sim 0.1–10\mathrm{PeV}$ neutrinos through photomeson interactions with x-ray photons. The large x-ray fluence ($7\times {10}^{-4}\mathrm{erg}{\mathrm{cm}}^{-2}$) and high photopion efficiency, together with the insignificant cooling of secondary mesons, result in bright neutrino emission expected from Sw $J1644+57$ if the jet composition is matter-dominated. One to several neutrinos may be detected by a ${\mathrm{Km}}^3$-scale detector from one tidal disruption event similar to Sw $J1644+57$, thereby providing a powerful probe of the composition of the jets.

• Received 9 June 2011

DOI:https://doi.org/10.1103/PhysRevD.84.081301