Distinguishing Tidal Disruption Events from Impostors
  Recent claimed detections of tidal disruption events (TDEs) in
multi-wavelength data have opened potential new windows into the evolution and
properties of otherwise dormant supermassive black holes (SMBHs) in the centres
of galaxies. At present, there are several dozen TDE candidates, which share
some properties and differ in others. The range in properties is broad enough
to overlap other transient types, such as active galactic nuclei (AGN) and
supernovae (SNe), which can make TDE classification ambiguous. A further
complication is that "TDE signatures" have not been uniformly observed to
similar sensitivities or even targeted across all candidates. This chapter
reviews those events that are unusual relative to other TDEs, including the
possibility of TDEs in pre-existing AGN, and summarises those characteristics
thought to best distinguish TDEs from continuously accreting AGN, strongly
flaring AGN, SNe, and Gamma-Ray Bursts (GRBs), as well as other potential
impostors like stellar collisions, "micro-TDEs," and circumbinary accretion
flows. We conclude that multiple observables should be used to classify any one
event as a TDE. We also consider the TDE candidate population as a whole,
which, for certain host galaxy or SMBH characteristics, is distinguishable
statistically from non-TDEs, suggesting that at least some TDE candidates do in
fact arise from SMBH-disrupted stars.
