Supermassive black holes preserve information on the growth of the host galaxy and its dynamic evolution. Thus, constraining their parameters is crucial to shed light on their formation and evolution. In recent years, X-ray astronomy has undergone a renaissance, with several instruments that perform large observational campaigns and cover an extremely wide range of energy timescales to study...
X-ray reverberation mapping studies of AGN can, in principle, be used to measure the black hole mass and spin, the accretion disc and corona geometries, and the ionisation state of the disc. We report on our efforts to fit the spectra and time lags of a number of AGN, but focus primarily on two sources, 1H 0707-495 and IRAS 13224-3809. We can explain the low- and high-frequency lags, find that...
The hard X-ray emission universally found in AGN is believed to be produced in the so-called corona, of which the physical nature remains unclear. A fundamental parameter is the coronal temperature ($T_{\rm c}$), which could be measured by fitting the high-energy cutoff ($E_{\rm cut}$) in the hard X-ray spectra. With multiple NuSTAR observations, we search for the variation of $T_{\rm...
We present a study of the ensemble X-ray variability of Active Galactic Nuclei (AGN) over a large range of timescales (20 ks ≤ T ≤ 14 yrs), redshift (0 ≤ z ≲ 3), luminosities ($10^{40} \leq L_X \leq 10^{46}\ \mbox{erg s}^{−1}$) and black hole (BH) masses $10^6≤M_⊙≤10^9$). Through the use of the "variance–frequency diagram", as a viable alternative to the power spectral density (PSD), we show...
One of the most influential relations in extragalactic astrophysics is the one that links the stellar-mass component of galaxies (Mstar) to the masses of the supermassive black holes (MBH) at their centres. Observational constraints on the shape, normalisation and redshift evolution of the Mstar-MBH relation provide important clues on the co-evolution of galaxies and their supermassive...
I will present the analysis of the X-ray variability properties of the Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS) using XMM-Newton observations. This sample includes more than 500 observations of 151 local AGN (medium redshift z=0.06). The aim of this work is to constrain the relation between the common estimators of the variability amplitude (i.e., fractional...
Temporal variability of flux across the electromagnetic spectrum is a commonly observed phenomenon in Active Galactic Nuclei (AGN), however the phenomenon is not well studied in low accretion rate AGN, primarily due to difficulties identifying them in X-ray catalogues due to their lower luminosity.
In this work, we use our algorithm EXODUS, which searches for variability in the whole of...
I present the analysis of a sample of several hundred SDSS quasars with multiple serendipitous XMM-Newton observations. The X-ray to UV luminosity relation allows to predict the average X-ray flux, and to select only the X-ray observations that are deep enough to remove any bias towards higer-than-average flux states. The optical/UV SDSS spectrum allows to investigate the relation between...
We present the first X-ray polarimetric measurements of three Seyfert 1 galaxies with IXPE, the NASA/ASI mission operating as of December 2021. The results allow us to directly constrain the geometrical shape of the hot corona for the first time. We discuss the implications for the physical interpretation of X-ray variability in these sources.
