We present multi-wavelength observations of PS16dtm ( also known as SN 2016ezh ) , an optically discovered super-luminous transient that occurred at the nucleus of SDSSJ015804.75-005221.8 , a known Narrow-line Seyfert 1 galaxy hosting a \sim 10 ^ { 6 } M _ { \odot } black hole .
The transient was previously claimed to be a Type IIn SLSN due to its luminosity and hydrogen emission lines .
The light curve shows that PS16dtm brightened by about two magnitudes in \sim 50 days relative to the archival host brightness and then exhibited a plateau phase for about \sim 100 days followed by the onset of fading in the UV .
During the plateau PS16dtm showed no color evolution , maintained a steady blackbody temperature of \sim 1.7 \times 10 ^ { 4 } K , and radiated at approximately the Eddington luminosity of the supermassive black hole .
The spectra , spanning UV to near-IR , exhibit multi-component hydrogen emission lines and strong Fe ii emission complexes , show little evolution with time , and closely resemble the spectra of NLS1 galaxies while being distinct from those of Type IIn SNe .
In addition , PS16dtm is undetected in the X-rays by Swift /XRT to a limit an order of magnitude below an archival XMM-Newton detection of its host galaxy .
These observations strongly link PS16dtm to activity associated with the supermassive black hole and are difficult to reconcile with a SN origin .
Moreover , the properties of PS16dtm are unlike any known form of AGN variability , and therefore we argue that it is a tidal disruption event in which the accretion of the stellar debris powers the rise in the continuum and excitation of the pre-existing broad line region , while at the same time providing material that obscures the X-ray emitting region of the pre-existing AGN accretion disk .
A detailed TDE model fits the bolometric light curve and indicates that PS16dtm will remain bright for several years ; we further predict that the X-ray emission will reappear on a similar timescale as the accretion rate declines .
Finally , we place PS16dtm in the context of other TDEs and find that tidal disruptions in active galaxies are an order of magnitude more efficient and reach Eddington luminosities , likely due to interaction of the stellar debris with the pre-existing accretion disk .