Reverberation and Spectral Variability of AGN

  • George B Presland

Student thesis: Master's ThesisMaster of Science (MSc)


In this thesis we explore the spectra and time variability of Active Galactic Nuclei (AGN). Time delays between the X-ray emission from different energy bands provides a powerful probe of the accretion flow and astrophysics of the central engines of these objects. We expand on two techniques: spectral plotting and timing analysis. We make use of all available XMM-Newton observations of five well-studied AGN: NGC 1365, NGC 4051, 1H0707-495, IRAS13224-3809 and MCG-6-30-15 have been analysed using existing and newly developed, unbiased techniques. These different analysis methods are evaluated, for their strengths and weaknesses. The goal of this research is to present a clear picture of several different methods of AGN spectral-timing analysis. We present results from five AGN using these techniques, from a total of 5.6 million seconds of analysed observations. Through the use of three-dimensional lag plots we have reliably identified hard lags in 1H0707-495, IRAS 13224-3809, MCG-6-30-15 and NGC 4051. Soft lags have been identified in 1H0707, IRAS 13224, possibly in NGC 4051 and for the first time in MCG-6-30-15. We find that plausible physical models to explain the energy and frequency dependent time lags have multiple connected components that couple the spectral and timing changes in the disk and corona. This shows that better, global models are required to simultaneously fit the spectra and time lags across all energies and frequency ranges. Constraining these models will be much easier with higher signal-to-noise observation by future observatories such as Athena (Matt, 2019).
Date of Award21 Jan 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorAndrew J Young (Supervisor)

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