Radio observations of the tidal disruption event XMMSL1 J0740$-$85
  We present radio observations of the tidal disruption event candidate (TDE)
XMMSL1 J0740$-$85 spanning 592 to 875 d post X-ray discovery. We detect radio
emission that fades from an initial peak flux density at 1.6 GHz of $1.19\pm
0.06$ mJy to $0.65\pm 0.06$ mJy suggesting an association with the TDE. This
makes XMMSL1 J0740$-$85 at $d=75$ Mpc the nearest TDE with detected radio
emission to date and only the fifth TDE with radio emission overall. The
observed radio luminosity rules out a powerful relativistic jet like that seen
in the relativistic TDE Swift J1644+57. Instead we infer from an equipartition
analysis that the radio emission most likely arises from a non-relativistic
outflow similar to that seen in the nearby TDE ASASSN-14li, with a velocity of
about $10^4$ km s$^{-1}$ and a kinetic energy of about $10^{48}$ erg, expanding
into a medium with a density of about $10^2$ cm$^{-3}$. Alternatively, the
radio emission could arise from a weak initially-relativistic but decelerated
jet with an energy of $\sim 2\times 10^{50}$ erg, or (for an extreme disruption
geometry) from the unbound debris. The radio data for XMMSL1 J0740$-$85
continues to support the previous suggestion of a bimodal distribution of
common non-relativistic isotropic outflows and rare relativistic jets in TDEs
(in analogy with the relation between Type Ib/c supernovae and long-duration
gamma-ray bursts). The radio data also provide a new measurement of the
circumnuclear density on a sub-parsec scale around an extragalactic
supermassive black hole.
