Tracing the AGN/X-ray Binary Analogy with Light Curves of Individual Changing-Look AGN
| Autor: | Ruan, John J., Anderson, Scott F., Eracleous, Michael, Green, Paul J., Haggard, Daryl, MacLeod, Chelsea L., Runnoe, Jessie C., Sobolewska, Malgosia A. |
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| Rok vydání: | 2019 |
| Předmět: | |
| DOI: | 10.48550/arxiv.1909.04676 |
| Popis: | 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. Comment: 14 pages, 5 figures. ApJ submitted |
| Databáze: | OpenAIRE |
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