The TDE ASASSN-14li and its host resolved at parsec scales with the EVN
  We report European Very Long Baseline Interferometry Network (EVN) radio
continuum observations of ASASSN-14li, one of the best studied tidal disruption
events (TDEs) to date. At 1.7 GHz with ~12x6mas resolution, the emission is
unresolved. At 5.0 GHz with ~3x2mas resolution, the radio emission shows an
extended structure that can be modeled with two components: a core-like
component and a fainter, possibly elongated source 4.3mas (~2pc) away. Our
observations are not conclusive as to the nature of the components, but three
scenarios are discussed. One possibility is a core-jet/outflow morphology, thus
making of ASASSN-14li the first TDE jet/outflow directly imaged. For this case,
the projected separation between the two components can only be explained by
superluminal motion, rather than the lower velocities inferred from
low-resolution radio observations. However, typical fast moving jets have
brightness temperatures ~5 orders of magnitude higher than we find, thus making
this scenario less likely. The second possibility is that we are imaging a
non-relativistic jet from past AGN/TDE activity. In this case a past TDE is
preferred given that the spatial extension and radio luminosity of the
elongated component are consistent with the theoretical predictions for a TDE
outflow. Alternatively, the two sources could indicate the presence of a binary
black hole, which would then naturally explain the enhanced TDE rates of
post-starburst galaxies. Future EVN observations will help us to distinguish
between these scenarios.
