Studying eclipse-like behaviour in two AGN: NGC 6814 and Zw 229.015

Abstract

Studying transient events in active galactic nuclei (AGN) can provide useful information about the AGN environment. In this work, transient-like events in NGC 6814 and Zw 229.015 were studied. Colour-colour grids, which provide better time resolution than spectral analysis and can break model degeneracies, were applied to the eclipse data for NGC 6814. These grids revealed a complex multi-cloud geometry for the obscurer, dismissing the original idea of a single, homogeneous cloud. In Zw 229.015, flux-resolved spectral analysis was used to study a concurrent dip in both the UV and X-ray light curves. The analysis attributed the likely source of the flux dip to continuum changes through either coronal variability or accretion rate changes. Timescale consideration revealed thermal processes to be the source of the variability causing the dip. Separate analyses of two different AGN showing similar transient-like behaviour, require different explanations.