Investigating the X-ray properties of a binary SMBH candidate: the case of MCG+11-11-032

In the framework of galaxy formation and evolution, SMBH binaries (SMBHB) are expected to be the natural outcome of galaxy mergers. My thesis project consists of the study of MCG+11-11-032, a radio-quiet Seyfert 2 galaxy (i.e. obscured) at z = 0.0362, identified as a promising SMBHB candidate (Severgnini+18). The X-ray emission is investigated through Swift-XRT monitoring campaigns, comprised of both proprietary and archival datasets for a total of 330 ksec of observational time over a period of ∼ 15 years. The X-ray modelling is highly sensitive to the source variability, observed in the modulation of the 0.2-10 keV XRT light curve and in the 15-150 keV BAT-123 months light curve (from which, a ∼ 25 months period was estimated, Serafinelli+20). Different physical mechanisms may be responsible for the source variability pattern, e.g. periodic accretion flows from the circumbinary accretion disk toward the mini-disks surrounding each BH. The double-peaked Fe Kα emission lines identified in the XRT spectra can be ascribed to the AGN orbital motion which can cause the lines to be Doppler-shifted and not detected at the rest-frame energy of 6.4 keV. Different spectral binning and summing procedure are considered in my work, in order to shed light in particular on line variability on different timescales. This is the preliminary, observational step needed to possibly interpret the complex variability behaviour of the emission lines of MCG+11-11-32 in the framework of mini and circumbinary disks models, predicted by many theoretical studies (e.g. Dotti+12). The properties of MCG+11-11-032 are still under discussion, since additional XRT monitorings are needed to place the results obtained so far on a more solid ground. Despite all the candidate sources currently known, the study of dual and binary AGN is still in its infancy. Future facilities, like SKA in the radio, LISA for GW and NewAthena in X-rays, would definitively provide large sample of binary candidates.