Magnetized Accretion Disks with Outflows for Changing-look AGNs

Abstract

Changing-look active galactic nuclei (CL-AGNs) challenge the standard accretion theory, owing to their rapid variability. Recent numerical simulations have shown that, for the sub-Eddington accretion case, the disk is magnetic pressure–dominated, thermally stable, and geometrically thicker than the standard disk. In addition, outflows were found in the simulations. Observationally, high blueshifted velocities absorption lines indicate that outflows exist in AGNs. In this work, based on the simulation results, we investigate the magnetic pressure–dominated disk, and find that the accretion timescale is significantly shorter than that of the standard thin disk. However, such a timescale is still longer than that of the CL-AGNs. Moreover, if the role of outflows is taken into account, then the accretion timescale can be shortened even further. By the detailed comparison of the theoretical accretion timescale with the observations, we propose that the magnetic pressure–dominated disk incorporating outflows can be responsible for the rapid variability of CL-AGNs.

Keywords

• Accretion
• Active galactic nuclei
• Galaxy accretion disks
• Magnetic fields