Tracing the AGN/X-ray Binary Analogy with Light Curves of Individual Changing-Look AGN

Abstract

Physical models of X-ray binary outbursts can aid in understanding the origin of 'changing-look' active galactic nuclei (AGN), if we can establish that these two black hole accretion phenomena are analogous. Previously, studies of the correlation between the UV-to-X-ray spectral index alpha_OX and Eddington ratio using single-epoch observations of changing-look AGN samples have revealed possible similarities to the spectral evolution of outbursting X-ray binaries. However, direct comparisons using multi-epoch UV/X-ray light curves of individual changing-look AGN undergoing dramatic changes in Eddington ratio have been scarce. Here, we use published Swift UV/X-ray light curves of two changing-look AGN (NGC 2617 and ZTF18aajupnt) to examine the evolution of their alpha_OX values during outburst. We show that the combination of these two changing-look AGN can trace out the predicted spectral evolution from X-ray binary outbursts, including the inversion in the evolution of alpha_OX as a function of Eddington ratio. We suggest that the spectral softening that is observed to occur below a critical Eddington ratio in both AGN and X-ray binaries is due to reprocessing of Comptonized X-ray emission by the accretion disk, based on the X-ray to UV reverberation lags previously observed in NGC 2617. Our results suggest that the physical processes causing the changing-look AGN phenomenon are similar to those in X-ray binary outbursts.

14 pages, 5 figures. ApJ submitted

References in corpus (6)

• The Zwicky Transient Facility: Science Objectives
• 1ES 1927+654: An AGN Caught Changing Look on a Timescale of Months
• Understanding extreme quasar optical variability with CRTS: II. Changing-state quasars
• A New Class of Changing-Look LINERs
• The Sloan Digital Sky Survey Reverberation Mapping Project: Accretion and Broad Emission Line Physics from a Hypervariable Quasar
• Mechanism of the Changing Look phenomenon in Active Galactic Nuclei

Cited by in corpus (6)

• X-ray binary accretion states in Active Galactic Nuclei? Sensing the accretion disc of supermassive black holes with mid-infrared nebular lines
• Long-term and multi-wavelength evolution of a changing-look AGN Mrk 1018
• The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566
• A compact core-jet structure in the changing-look Seyfert NGC 2617
• Changing looks of the nucleus of the Seyfert galaxy NGC 1566 compared with other changing-look AGNs
• The Awakening Beast in the Seyfert 1 Galaxy KUG 1141+371 I