The evolution of the UV/optical lag spectrum of NGC 7469 seen by the Liverpool Telescope

TL;DR

This study analyzes the UV/optical lag spectrum of AGN NGC 7469 over four months, revealing changes in lag behavior that suggest complex, evolving geometries in reverberation models.

Contribution

It provides the first detailed temporal analysis of lag spectrum evolution in NGC 7469, highlighting the need for complex models of AGN variability.

Findings

Lag spectrum changed between two observation periods

Different variability components dominate at different times

Reverberation models must account for complex geometries

Abstract

We present the results regarding the analysis of an intensive monitoring of the Active Galactic Nucleus (AGN) NGC 7469. We observed the source for 4 months with almost daily cadence in the ugriz bands, using the IO:O on the Liverpool Telescope. We measured the lags with respect to the u band and found a clear change of the lag spectrum between the first and the second half of the campaign. Given that the source varies on different timescales during these two segments, it is likely that different components are dominating the variability at different times. This result further confirms that reverberation models require a more complex geometry than a static illuminating point source and that particular attention has to be given in the interpretation of these delays.