A magnetic accretion disk-outflow model for changing look active galactic nuclei

TL;DR

This paper proposes a magnetic accretion disk-outflow model to explain the rapid variability in changing look AGNs, showing that magnetic outflows can significantly shorten inflow times to match observed timescales.

Contribution

It introduces a magnetic disk-outflow model that accounts for short-term variability in CL AGNs, differing from traditional viscous disk models.

Findings

Inflow times of several years to tens of years are achievable with magnetic outflows.

The model spectra fit the observed spectra of Mrk 1018 in both low and high states.

Inflow time varies from about 5 years in high state to 20 years in low state, consistent with observations.

Abstract

The time-scales of the variabilities in changing look (CL) active galactic nuclei (AGNs) are usually at the order of years to tens of years (some of them are even shorter than one year), which are much shorter than the viscous timescale of a standard thin accretion disk. It implies that the variabilities of CL AGNs cannot be reproduced by varying the mass accretion rate of the thin disk. In this work, we employ a magnetic accretion disk-outflow model to calculate the inflow time of the disk predominantly driven by magnetic outflows. In this model, most angular momentum of the gas in the disk is carried away by the outflows, and therefore its radial velocity can be substantially higher than that of a conventional viscous disk. Our calculations show that the inflow time of such a disk with outflows can be around several years to tens years. The calculated spectra of the disk with outflows can fit the observed spectra of a CL AGN Mrk 1018 quite well both in the low and high states. The derived inflow time of such a disk with outflows is around 5 years in the high state, while it becomes $\sim 20$ years in the low state, which is roughly consistent with the observations of the variabilities in Mrk 1018.