Spectroscopic monitoring of the candidate tidal disruption event in
  F01004-2237
  We present results of spectroscopic monitoring observations of the
Ultra-Luminous Infra Red Galaxy F01004-2237. This galaxy was observed to
undergo changes in its optical spectrum, detected by comparing a spectrum from
2015 with one from 2000. These changes were coincident with photometric
brightening. The main changes detected in the optical spectrum are enhanced He
II $\lambda$4686 emission and the appearance of He I
$\lambda$3898,$\lambda$5876 emission lines. The favoured interpretation of
these changes was that of a tidal disruption event (TDE) happening in 2010.
However, subsequent work suggested that these changes are caused by another
hitherto unknown reason related to variations in the accretion rate in the
active galactic nucleus (AGN). Our optical spectroscopic monitoring
observations show that the evolution of the He lines is in line with the
evolution seen in TDEs and opposite of what observed from reverberation mapping
studies of AGNs, renewing the discussion on the interpretation of the flare as
a TDE.
