Clues for the accretion-regulated dust torus in the changing-look active galactic nucleus SDSS J101152.98+544206.4

The dust torus plays the key role in determining the observational appearance of active galactic nuclei (AGNs). We test the scenario of an accretion-regulated central dust torus for the first time in the individual changing-look AGN (CLAGN) SDSS J1011+5442. Based on the dependence of the broad-line Hα luminosity on the continuum luminosity, the scenario of moving dust clouds can be ruled out in SDSS J1011+5442. Meanwhile, the virial black hole mass in the bright state is consistent with the mass through the M-σ relation, indicating that virialization assumptions are efficient in central broad-line regions (BLRs). However, the virial black hole mass determined in the dim state is 60 times lower than the value through the M-σ relation. The differing properties of broad-line Hα in different states are naturally explained by the scenario of an accretion-regulated dust torus. Below a critical Eddington ratio, the opening angle of the dust torus declines with increasing accretion rate, and only the outer part of central BLRs is therefore detected for broad-line Hα, with smaller line widths detected in the dim state, but all BLRs are detected in the bright state. Our results not only indicate that the properties of the central dust torus clearly affect the variability properties of changing-look AGNs, but also indicate that the study of changing-look AGNs might provide further clues for dynamical evolving models for a dust torus in AGNs.