Related papers: Revisiting UV/optical continuum time lags in AGN

Over the last 12 years, AGN monitoring by RXTE, has revolutionised our understanding of the X-ray variability of AGN, of the relationship between AGN and Galactic black hole X-ray binaries (BHBs) and hence of the accretion process itself,…

The primary X-ray emission in active galactic nuclei (AGN) originates in a compact region called the corona located very close to the super-massive black hole and the accretion disk. The knowledge of the cut-off energy ($E_{cut}$) of the…

To address the discrepancy where disk sizes exceed those predicted by standard models, we explore two extensions to disk size estimates within the UV/optical wavelength range: disk winds and color correction. We provide detailed,…

We report the detection of a long-timescale negative lag, where the blue bands lag the red bands, in the nearby Seyfert 1 galaxy Fairall 9. Active Galactic Nuclei (AGN) light curves show variability over a wide range of timescales. By…

Accreting supermassive black holes at the centres of galaxies are the engine of active galactic nuclei (AGN). X-ray light curves of unabsorbed AGN show dramatic random variability on timescales ranging from seconds to years. The power…

We present a broadband study of the WLQ SDSS J101353.45+492758.1, which displays a nearly featureless UV-optical spectrum with only a weak Mg II line alongside an exceptionally low X-ray flux. We model its spectral energy distribution using…

The 2-10 keV continuum of AGN is well represented by a single power law, generally attributed to a hot comptonizing medium, such as a corona above the accretion disk. At smaller energies the continuum displays an excess with respect to the…

We study accretion disk-corona connection in Seyfert 1 galaxies using simultaneous UV/X-ray observations of NGC 4593 (July 14-18, 2016) and NGC 7469 (October 15-19, 2017) performed with AstroSat. We use the X-ray (0.5-7.0 keV) data acquired…

We discuss the application of simple relativistically-blurred X-ray reflection models to the determination of the spin and the inner radius of the disc in accreting black holes. Observationally, the nature of the corona is uncertain a…

The cosmic history of supermassive black hole (SMBH) growth is important for understanding galaxy evolution, reionization and the physics of accretion. Recent NuSTAR, Swift-BAT and \textit{Chandra} hard X-ray surveys have provided new…

We analyze the broadband photometric light curves of Seyfert 1 galaxies from the Sergeev et al. (2005) sample and find that a) perturbations propagating across the continuum emitting region are a general phenomenon securely detected in most…

X-ray variability provides a powerful probe of the innermost regions of active galactic nuclei (AGNs), offering valuable insights into the accretion process and the structure of the corona. Previous studies have established a correlation…

We exhibit, by compiling all data sets we can acquire, that the Fourier frequency dependent hard X-ray lags, first observed in the analysis of aperiodic variability of the light curves of the black hole candidate Cygnus X-1, appear to be a…

Observation of the bright Seyfert 1 galaxy RE J1034+396 is believed to demonstrate a drift of the central period of the Quasi Periodic Oscillation (QPO) linearly correlated with the temporary X-ray luminosity. We show, using a specific…

After reviewing the basic physics of X-ray reflection in AGN, we present three case studies which illustrate the current state of X-ray reflection studies. For the low-luminosity AGN NGC4258, we find that the iron line is much narrower than…

Accretion states, which are universally observed in stellar-mass black holes in X-ray binaries, are also anticipated in active galactic nuclei (AGN). This is the case at low luminosities, when the jet-corona coupling dominates the energy…

Variable continuum emission from AGN can be used to probe the structure of their accretion disks via reverberation mapping. Assuming a variable, hot inner light source irradiates the surrounding accretion disk, time delays between different…

As matter accretes onto the central supermassive black holes in active galactic nuclei (AGN), X-rays are emitted. We present a population synthesis model that accounts for the summed X-ray emission from growing black holes; modulo the…

Relativistic reflection features in the X-ray spectra of accreting black holes are considered to be generated by the illumination of the accretion disk by the hot corona. In this work, we present a numerical method for the emission line…

Ultraluminous X-ray sources (ULXs) are X-ray binary systems containing an accreting neutron star (NS) or black hole emitting at luminosities above the Eddington limit of a $10M_{\odot}$ black hole. Approximately 1900 (either confirmed or…