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Tidal disruption events (TDEs) occur when a star gets torn apart by asupermassive black hole as it crosses its tidal radius. We present late-timeoptical and X-ray observations of the nuclear transient AT2019qiz, which showedthe typical signs of an optical-UV transient class commonly believed to beTDEs. Optical spectra were obtained 428, 481 and 828 rest-frame days afteroptical lightcurve peak, and a UV/X-ray observation coincided with the laterspectrum. The optical spectra show strong coronal emission lines, including [FeVII], [Fe X], [Fe XI] and [Fe XIV]. The Fe lines rise and then fall, except [FeXIV] which appears late and rises. We observe increasing flux of narrow H-alphaand H-beta and a decrease in broad H-alpha flux. The coronal lines have FWHMsranging from ~150 - 300km/s, suggesting they originate from a region betweenthe broad and narrow line emitting gas. Between the optical flare and late-timeobservation, the X-ray spectrum softens dramatically. The 0.3-1 keV X-ray fluxincreases by a factor of ~50 while the hard X-ray flux decreases by a factor of~6. WISE fluxes also rose over the same period, indicating the presence of aninfrared echo. With AT2017gge, AT2019qiz is one of two examples of aspectroscopically-confirmed optical-UV TDE showing delayed coronal lineemission, supporting speculations that Extreme Coronal Line Emitters inquiescent galaxies can be echos of unobserved past TDEs. We argue that thecoronal lines, narrow lines, and infrared emission arise from the illuminationof pre-existing material likely related to either a previous TDE or AGNactivity.

Delayed Appearance and Evolution of Coronal Lines in the TDE AT2019qiz