Abstract
Cosmic neutrinos provide a unique window into the otherwise-hidden mechanism
of particle acceleration in astrophysical objects. A flux of high-energy
neutrinos was discovered in 2013, and the IceCube Collaboration recently
associated one high-energy neutrino with a flare from the relativistic jet of
an active galaxy pointed towards the Earth. However a combined analysis of many
similar active galaxies revealed no excess from the broader population, leaving
the vast majority of the cosmic neutrino flux unexplained. Here we present the
association of a radio-emitting tidal disruption event (AT2019dsg) with another
high-energy neutrino, identified as part of our systematic search for optical
counterparts to high-energy neutrinos with the Zwicky Transient Facility (ZTF).
The probability of finding any radio-emitting tidal disruption event by chance
is 0.5%, while the probability of finding one as bright in bolometric energy
flux as AT2019dsg is 0.2%. Our electromagnetic observations can be explained
through a multi-zone model, with radio analysis revealing a central engine,
embedded in a UV photosphere, that powers an extended synchrotron-emitting
outflow. This provides an ideal site for PeV neutrino production. The
association suggests that tidal disruption events contribute to the cosmic
neutrino flux. Unlike previous work which considered the rare subset of tidal
disruption events with relativistic jets, our observations of AT2019dsg suggest
an empirical model with a mildly-relativistic outflow.
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