14 papers
X-ray disc reverberation modelling of the X-ray/UV/optical spectral/timing properties of Fairall 9
M. Polioudakis, M. Papoutsis, I. E. Papadakis +3
Multiwavelength monitoring surveys of active galactic nuclei (AGN) have revealed correlated variability observed in the X-ray, UV, and optical bands. X-ray reverberation, arising f…
Consistency between X-ray and UV-Optical reverberation measurements in NGC 5548
Amit Kumar Mandal, Bożena Czerny, Michal DovÄiak +2
The hard X-rayemitting hot corona is a key component of active galaxies. Constraints on the hot corona height can be derived from reverberation studies in both the X-ray and opt…
Disk reflection as the origin of the X-ray polarization of NGC 4151 with IXPE
E. Kammoun, M. DovÄiak, J. Podgorný +6
We present an X-ray spectro-polarimetric study of the nearby type-1 active galactic nucleus NGC 4151 using two long IXPE observations obtained in 2022 and 2024, supported by simult…
Energy dependence of the X-ray power spectrum in NGC4051 and NGC4395
V. A. Diamantopoulos, I. E. Papadakis, A. Akylas +3
Active galactic nuclei (AGNs) exhibit strong variability across the electromagnetic spectrum on a wide range of timescales, particularly in X-rays where fluctuations are both rapid…
The ensemble broad-frequency power spectrum of Stripe-82 quasars from multiple surveys
Vincenzo Petrecca, Iossif E. Papadakis, Maurizio Paolillo +5
Variability is a striking features of quasars, observed at all timescales wavelengths. Studying its properties and the correlations with the physical parameters (e.g. black hole ma…
Characterising the X-ray variability of QSOs to the highest Eddington ratios and black hole masses with eROSITA light curves
Antonis Georgakakis, Angel Ruiz, Johannes Buchner +9
An important diagnostic of the inner structure of accretion flows onto supermassive black holes are the stochastic flux variations at X-ray wavelengths. Despite its significance, a…