On the time delay evolution of five Active Galactic Nuclei

TL;DR

This study examines the evolution of time delays in the light curves of five active galactic nuclei, revealing significant variations during high luminosity periods and discussing methodological challenges in measuring these delays.

Contribution

It introduces a Gaussian-kernel based estimator to analyze the time evolution of delays in AGN light curves, highlighting its application and limitations.

Findings

Largest delay variations occur during high luminosity periods.

Method shows instability for some AGNs possibly due to numerical issues.

Temporal delay variations in Arp 102B may reflect real physical changes.

Abstract

Here we investigate light curves of the continuum and emission lines of five type 1 active galactic nuclei (AGN) from our monitoring campaign, to test time-evolution of their time delays.Using both modeled and observed AGN light curves we apply Gaussian-kernel based estimator to capture variation of local patterns of their time evolving delays. The largest variations of time delays of all objects occur in the period when continuum or emission lines luminosity is the highest. However, Gaussian kernel based method shows instability in the case of NGC 5548, 3C 390.3, E1821+643 and NGC 4051 possible due to numerical discrepancies between Damped Random Walk (DRW) time scale of light curves and sliding time windows of the method. The temporal variations of time lags of Arp 102B can correspond to the real nature of the time lag evolution.