An X-ray View of the Ambiguous Nuclear Transient AT2019pev
Speakers: Ilaria Viale (Università degli Studi di Padova)
AT2019pev is a nuclear transient in a narrow-line Seyfert 1 galaxy at𝑧=0096. The archivalultraviolet, optical and infrared data showed features of both tidal disruption events (TDEs)and active galactic nuclei (AGNs), and its nature is not fully understood. We present detailedX-ray observations of AT2019pev taken withSwift, Chandra and NICER over 173 days of itsevolution since the firstSwiftXRT epoch. The X-ray luminosity increases by a factor of fivein five days from the firstSwiftXRT epoch to the lightcurve peak. The lightcurve decays by afactor of ten over?75 days and then flattens with a weak re-brightening trend at late times. TheX-ray spectra show a "harder-when-brighter" trend before peak and a "harder-when-fainter"trend after peak, which may indicate a transition of accretion states. The archival ground-basedoptical observations show similar time evolution as the X-ray lightcurves. Beyond the seasonallimit of the ground-based observations, the Gaia lightcurve is rising toward an equally bright orbrighter peak 223 days after the optical discovery. Combining our X-ray analysis and archivalmulti-wavelength data, AT2019pev more closely resembles an AGN transient.