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Journal article
Investigating non-linear and stochastic hard X-ray variability of active galactic nuclei using recurrence analysis
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, v 518(3), p4372
Jan 2023
Abstract
We present results of recurrence analysis of 46 active galactic nuclei (AGNs) using light curves from the 157-month catalogue of the Swift Burst Alert Telescope (BAT) in the 14-150 keV band. We generate recurrence plots and compute recurrence plot metrics for each object. We use the surrogate data method to compare all derived recurrence-based quantities to three sets of stochastic light curves with identical power spectrum, flux distribution, or both, in order to determine the presence of determinism, non-linearity, entropy, and non-stationarity. We compare these quantities with known physical characteristics of each system, such as black hole mass, Eddington ratio, and bolometric luminosity, radio loudness, obscuration, and spectroscopic type. We find that almost all AGNs in this sample exhibit substantial higher order modes of variability than is contained in the power spectrum, with approximately half exhibiting non-linear or non-stationary behaviour. We find that Type 2 AGNs are more likely to contain deterministic variability than Type 1 AGNs, while the same distinction is not found between obscured and unobscured AGNs. The complexity of variability among Type 1 AGNs is anticorrelated with Eddington ratio, while no relationship is found among Type 2 AGNs. The connections between the recurrence properties and AGN class suggest that hard X-ray emission is a probe of distinct accretion processes among classes of AGNs, which supports interpretations of changing-look AGNs and challenges the traditional unification model that classifies AGNs only on viewing angle.
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- Title
- Investigating non-linear and stochastic hard X-ray variability of active galactic nuclei using recurrence analysis
- Publication Details
- MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, v 518(3), p4372
- Publisher
- OXFORD UNIV PRESS; OXFORD
- Grant note
- RAP is grateful for support from the NASA Education Minority University Research Education Project (MUREP) through the NASA Harriett G. Jenkins Graduate Fellowship activity under Grant No. 80NSSC19K1291. RAP also acknowledges support for this work provided by the National Science Foundation MPS-Ascend Postdoctoral Research Fellowship under Grant No. 2138155. The authors thank the anonymous referee for comments that substantially improved the manuscript.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Drexel University
- Web of Science ID
- WOS:000893941000007
- Scopus ID
- 2-s2.0-85159174076
- Other Identifier
- 991021861311204721
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- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Astronomy & Astrophysics