Coevolution of Broad Emission Lines and X-Ray Spectrum in Changing-look AGNs

Abstract Changing-look active galactic nuclei (CLAGNs) show the disappearance and reappearance of broad emission lines in a few years, which challenges orientation-based AGN unification model. We reduce X-ray data for five well-studied CLAGNs that strong change past several decades. find photon index, ?, Eddington-scaled luminosity, L 2–10 keV / Edd , normally follow negative positive correlations when Eddington ratio is lower higher than critical value ?10 ?3 . observed with H ? stay part ?– correlation, while become weak or disappear anticorrelation suggests evolution should be correlated underlying accretion process. further are consistent other different types AGNs bol – correlation. These results support belong to special stage bolometric ?1%, where easily affected by variation ionization luminosity caused transition modes.