On the Time Scales of Optical Variability of AGN and the Shape of Their Optical Emission Line Profiles

Edi Bon,Predrag Jovanović,Nataša Bon,Paola Marziani

doi:10.3390/atoms7010026

Abstract

The mechanism of the optical variability of active galactic nuclei (AGN) is still very puzzling. It is now widely accepted that the optical variability of AGN is stochastic, producing red noise-like light curves. In case they were to be periodic or quasi-periodic, one should expect that the time scales of optical AGN variability should relate to orbiting time scales of regions inside the accretion disks with temperatures mainly emitting the light in this wavelength range. Knowing the reverberation scales and masses of AGN, expected orbiting time scales are in the order of decades. Unfortunately, most of monitored AGN light curves are not long enough to investigate such time scales of periodicity. Here we investigate the AGN optical variability time scales and their possible connections with the broad emission line shapes.

Highlights

Active galactic nuclei (AGN) are very strong and variable emitters [1]
In case we could identify more than one significant period in their light curves that could be linked to the radius of amplified ring emission in the broad emission line shape, for each ring-radius pair we should expect to obtain the same mass of the central BH mass using a Kepler’s laws
Using the radii measured from line profile matching to the model, we measure the ring radii that we hoped to be connected to the variability quasi-periods, as a measurement of variability time scales

Summary

Introduction

It is widely believed that the AGN patterns correspond to red noise-like curves [2,3], as a result of unpredicted processes of fluctuations of their accretion disks (AD). In some cases, these variations appear periodic, with periodogram peak significance jumping above the red noise levels (see for example, [4]). Significant periodicities are detected in several AGN which are extensively monitored for sufficiently long time, such as OJ287 [4,5], NGC. 4151 [6,7,8], NGC 5548 [9,10], Ark 120 [11], 3c273 [12,13].

Methods

Results

Conclusion