How Long Will the Quasar UV/Optical Flickering Be Damped? II. the Observational Test

TL;DR

This study tests the relationship between AGN variability timescales and physical properties, confirming the Corona Heated Accretion disk Reprocessing model and highlighting the importance of sufficient light-curve length for accurate measurements.

Contribution

It provides an observational validation of the Corona Heated Accretion disk Reprocessing model's timescale predictions using well-defined AGN samples.

Findings

Confirmed consistency with the Corona Heated Accretion disk Reprocessing model

Empirical relations underestimate the characteristic timescale

Highlights the importance of long light curves for accurate variability analysis

Abstract

The characteristic timescale at which the variability of active galactic nuclei (AGNs) turns from red noise to white noise can probe the accretion physics around supermassive black holes (SMBHs). A number of works have studied the characteristic timescale of quasars and obtained quite different scaling relations between the timescale and quasar physical properties. One possible reason for the discrepancies is that the characteristic timescale can be easily underestimated if the light curves are not long enough. In this work, we construct well-defined AGN samples to observationally test the relationships between the characteristic timescale and AGN properties obtained by previous works. Our samples eliminate the effects of insufficient light-curve lengths. We confirm that the timescale predictions \citep{Zhou2024} of the Corona Heated Accretion disk Reprocessing model are consistent with our timescale measurements. The timescale predictions by empirically relations \citep[e.g.,][]{Kelly2009} are systematically smaller than our measured ones. Our results provide further evidence that AGN variability is driven by thermal fluctuations in SMBH accretion disks. Future flagship time-domain surveys can critically test our conclusions and reveal the physical nature of AGN variability.