The Growing Class of Ambiguous Nuclear Transients

Recently, an increasing number of nuclear transients have been discovered, including those that exhibit characteristics of both active galactic nuclei (AGNs) and tidal disruption events (TDEs). As such transients cannot easily be classified, we have dubbed them ambiguous nuclear transients (ANTs). Often residing in galaxies hosting a narrow-line AGN, these ANTs give us a unique window into the diversity of flaring behaviors associated with accretion onto supermassive black holes. ANTs have shown some broad trends, including a strong UV/optical excess like TDEs, and power-law X-ray spectra, similar to AGNs. However stark differences do exist between ANTs, such as a wide range in peak luminosities, photometric evolution, and the appearance and strength of broad emission lines. Here we summarize the current sample of ANTs, drawing comparisons to TDEs and AGN flares and discuss important future observations to deepen our understanding of these elusive nuclear transients.