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A tidal disruption event (TDE) involves the shredding of a star in theproximity of a supermassive black hole (SMBH). The nearby ($\approx$230 Mpc)relatively radio-quiet, thermal emission dominated source AT2019dsg is thefirst TDE with a potential neutrino association. The origin of non-thermalemission remains inconclusive; possibilities include a relativistic jet or asub-relativistic outflow. Distinguishing between them can address neutrinoproduction mechanisms. High-resolution very long baseline interferometry 5-GHzobservations provide a proper motion of 0.94 $\pm$ 0.65 mas yr$^{-1}$ ($3.2 \pm2.2~c$; $1-\sigma$). Modelling the radio emission favors an origin from theinteraction between a decelerating outflow (velocity $\approx$ 0.1 $c$) and adense circum-nuclear medium. The transition of the synchrotron self-absorptionfrequency through the observation band marks a peak flux density of 1.19 $\pm$0.18 mJy at 152.8 $\pm$ 16.2 days. An equipartition analysis indicates anemission region distance of $\geqslant$ 4.7 $\times$ 10$^{16}$ cm, magneticfield strength $\geqslant$ 0.17 G, and number density $\geqslant$ 5.7 $\times$10$^{3}$ cm$^{-3}$. The disruption involves a $\approx$ 2 $M_\odot$ star with apenetration factor $\approx 1$ and a total energy output of $\leqslant$ 1.5$\times$ 10$^{52}$ erg. The outflow is radiatively driven by accretion ofstellar debris onto the SMBH. Neutrino production is likely related to theacceleration of protons to PeV energies and the availability of a suitablecross-section at the outflow base. The present study thus helps excludejet-related origins for non-thermal emission and neutrino production, andconstrains non-jetted scenarios.

High-resolution VLBI observations of and modelling the radio emission from the TDE AT2019dsg