Variable ADAF disk as the origin of Changing-Look AGN

TL;DR

This paper proposes that variations in the size of the inner ADAF disk cause changing-look AGN transitions, linking accretion flow dynamics to observable spectral and jet phenomena.

Contribution

It introduces a model where ADAF size variations driven by turbulence explain changing-look AGN and unifies different AGN states considering both orientation and ADAF size.

Findings

ADAF size variations influence AGN spectral states.

Turbulence parameter fects accretion rate and jet formation.

Intermediate-to-large scale ADAFs may explain certain radio sources.

Abstract

We propose that changing-look AGN transitions arise from variations in the size of the inner ADAF disk. The AGN accretion disk consists of an outer thin disk and an inner thick ADAF component, whose size is intrinsically unstable and evolves over time. The size variations of the ADAF are governed by a parameter \eta, which represents the turbulence strength within the accretion flow. \eta also determines the accretion rate onto the central black hole and controls jet formation and outflow rate, with the latter regulating the line-of-sight absorption. From the perspective of a variable ADAF, changing-state and changing-observation AGN are two sides of the same coin. We further discuss gigahertz-peaked and compact steep-spectrum radio sources as possible manifestations of intermediate-to-large scale ADAFs. Finally, we propose that AGN unification models should include both orientation and ADAF size as key parameters.