On the Observational Difference between the Accretion Disk-Corona Connections among Super- And Sub-Eddington Accreting Active Galactic Nuclei

Hezhen Liu, B. Luo, W. N. Brandt, Michael S. Brotherton, S. C. Gallagher, Q. Ni, Ohad Shemmer, J. D. Timlin

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

We present a systematic X-ray and multiwavelength study of a sample of 47 active galactic nuclei (AGNs) with reverberation mapping measurements. This sample includes 21 super-Eddington accreting AGNs and 26 sub-Eddington accreting AGNs. Using high-state observations with simultaneous X-ray and UV/optical measurements, we investigate whether super-Eddington accreting AGNs exhibit different accretion disk-corona connections compared to sub-Eddington accreting AGNs. We find tight correlations between the X-ray-to-UV/optical spectral slope parameter (α OX) and the monochromatic luminosity at 2500 Å (L 2500Å) for both the super- and sub-Eddington subsamples. The best-fit α OX-L 2500Å relations are consistent overall, indicating that super-Eddington accreting AGNs are not particularly X-ray weak in general compared to sub-Eddington accreting AGNs. We find dependences of α OX on both the Eddington ratio (L Bol/L Edd) and black hole mass (M BH) parameters for our full sample. A multivariate linear regression analysis yields, with a scatter similar to that of the α OX-L 2500Å relation. The hard (rest-frame >2 keV) X-ray photon index (Γ) is strongly correlated with L Bol/L Edd for the full sample and the super-Eddington subsample, but these two parameters are not significantly correlated for the sub-Eddington subsample. A fraction of super-Eddington accreting AGNs show strong X-ray variability, probably due to small-scale gas absorption, and we highlight the importance of employing high-state (intrinsic) X-ray radiation to study the accretion disk-corona connections in AGNs.

Original languageEnglish (US)
Article number103
JournalAstrophysical Journal
Volume910
Issue number2
DOIs
StatePublished - Apr 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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