The effects of large-scale magnetic fields on the model for repeating changing-look AGNs

TL;DR

This paper investigates how large-scale magnetic fields influence the periodic outbursts in changing-look AGNs, showing they can significantly alter outburst periods and intensities, thereby explaining observed behaviors.

Contribution

It introduces the effects of magnetic fields on the limit cycle behavior of CL AGNs, expanding previous models by including magnetic wind influences.

Findings

Magnetic fields can reduce outburst periods in CL AGNs.

Magnetic fields can increase outburst intensities.

Other parameters like transition radius and disk viscosity also affect outburst behavior.

Abstract

Periodic outbursts are observed in several changing-look (CL) active galactic nuclei (AGNs). \citet{sniegowska_possible_2020} suggested a model to explain the repeating CL in these AGNs, where the periodic outbursts are triggered in a narrow unstable zone between an inner ADAF and outer thin disk. In this work, we intend to investigate the effects of large-scale magnetic fields on the limit cycle behaviors of CL AGNs. The winds driven by magnetic fields can significantly change the structure of thin disk by taking away the angular momentum and energy of the disk. It is found that the period of outburst in repeating CL AGNs can be substantially reduced by the magnetic fields. Conversely, if we keep the period unchanged, the outburst intensity can be raised for several times. These results can help to explain the observational properties of multiple CL AGNs. Besides the magnetic fields, the effects of transition radius $R_{\rm tr}$, the width of transition zone $\Delta R$ and Shakura-Sunyaev parameter $\alpha$ are also explored in this work.