Unique photometric variability in SDSS J134628.62+173659.5: clues for moving dust clouds as physical origin of changing-look AGN

TL;DR

This study investigates the photometric variability of a specific changing-look AGN, providing evidence that moving dust clouds, rather than accretion rate changes, can explain some observed phenomena.

Contribution

The paper offers robust observational evidence supporting moving dust clouds as a physical mechanism behind certain changing-look AGN, challenging the dominant accretion variation scenario.

Findings

Obscuration effects confirmed with >10σ confidence in SDSS J1346+1736.

Reddening variations from E(B-V)~1.26 to 0.55 explain broad emission line changes.

Probability of accretion rate variation scenario is only 3.2%."

Abstract

The scenario of variations in accreting process around central black hole has been widely accepted as the preferred physical origin of changing-look active galactic nuclei (CLAGN), rather than obscuration effects by moving dust clouds. In this manuscript, after analyzing long-term photometric variability in Type-1.8 AGN SDSS J1346+1736 with apparent broad H$\alpha$ but very weak broad H$\beta$, robust clues for obscurations can be confirmed with confidence level higher than 10$\sigma$. Then, based on obscurations related to moving dust clouds, from dark state with E(B-V)$\sim$1.26 to bright state with E(B-V)$\sim$0.55, apparent both broad H$\alpha$ and broad H$\beta$ can be clearly expected. Meanwhile, the expected line luminosity from reddening corrected continuum luminosity is consistent with the reddening corrected line luminosity, to support the obscuration effects. Furthermore, through symmetric features in the light curves, probability is only 3.2\% in SDSS J1346+1736 to support the scenario of variations of accretion rates traced by CAR process. Therefore, besides the more and more preferred scenario of variations in accreting process, the scenario of moving dust clouds could be more reasonable in some CLAGN with apparent variations in optical colors.