A concordance scenario for the observed neutrino from a tidal disruption event

During a tidal disruption event, a star is torn apart by the tidal forces of a supermassive black hole, with about 50% of the star’s mass eventually accreted by the black hole. The resulting flare can, in extreme cases of super-Eddington mass accretion, result in a relativistic jet^1–4. While tidal disruption events have been theoretically proposed as sources of high-energy cosmic rays^5,6 and neutrinos^7–14, stacking searches indicate that their contribution to the diffuse extragalactic neutrino flux is very low¹⁵. However, a recent association of a track-like astrophysical neutrino (IceCube-191001A¹⁶) with a tidal disruption event (AT2019dsg¹⁷) indicates that some tidal disruption events can accelerate cosmic rays to petaelectronvolt energies. Here we introduce a phenomenological concordance scenario with a relativistic jet to explain this association: an expanding cocoon progressively obscures the X-rays emitted by the accretion disk, while at the same time providing a sufficiently intense external target of backscattered X-rays for the production of neutrinos via proton–photon interactions. We also reproduce the delay (relative to the peak) of the neutrino emission by scaling the production radius with the black-body radius. Our energetics and assumptions for the jet and the cocoon are compatible with expectations from numerical simulations of tidal disruption events.