The X-ray Variability and Multiphase Winds of a Changing-Look AGN at z=0.149

Baldini, Pietro (2023) The X-ray Variability and Multiphase Winds of a Changing-Look AGN at z=0.149. [Laurea magistrale], Università di Bologna, Corso di Studio in Astrofisica e cosmologia [LM-DM270]
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According to the Active Galactic Nuclei (AGN) Unified Model, the main discriminant between AGN of different classifications is the viewing angle. The discovery of “Changing Look” AGN (CL-AGN), a subclass that shows drastic spectral variations on relatively short timescales, poses a threat to the static Unified Model and requires either a better understanding of accretion physics or the inclusion of more complex, dynamical processes. Characterizing such objects is of crucial importance in order to assess where our theories come short. 2MASS 0918+2117 (2M0918) is a CL-AGN, as witnessed by 2 XMM-Newton observations (respectively dating 2003 and 2005, Pounds & Wilkes 2007) which revealed an increase in its X-ray flux by a factor ∼ 10, possibly due to a decrease in obscuration. In this work we re-analyze the XMM-Newton spectra available in the archive, investigate the nature of the variability and interpret it in a dynamical framework. We do so by extending the light curve through dedicated 2020 XMM-Newton and NuSTAR follow-up observations and data from the first 4 eROSITA all-sky surveys. The 2005 spectrum shows tentative evidence of absorption features above 7.8 keV rest-frame, which can be interpreted as highly ionized and fast winds launched from the accretion disk, known as Ultra Fast Outflows (UFO). The feature is confirmed through the analysis of the 2020 X-ray spectra, where we detected at > 99% significance UFOs with v=0.15c. Overall the X-ray spectral properties of 2M0918 suggest a scenario in which winds play a crucial role in the displacement of obscuring material in and out of the line of sight. In addition, the 2005 SDSS optical spectrum reveals the presence of outflows in the ionized phase on kpc scale, with velocities up to 1000 km/s. The almost simultaneous detection of accretion disk- and galaxy-scale winds allows to constrain outflow propagation mechanisms, which is consistent with a momentum-driven scenario.

Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Baldini, Pietro
Relatore della tesi
Correlatore della tesi
Corso di studio
Ordinamento Cds
Parole chiave
AGN,Changing-Look AGN,CL-AGN,X-ray,AGN Variability,X-ray spectral analysis,AGN Feedback,UFO,High Energy Astrophysics,Black Hole Astrophysics,SMBH,eROSITA
Data di discussione della Tesi
17 Marzo 2023

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