Related papers: Rapid X-ray Variability of Seyfert 1 Galaxies
We present joint \textit{XMM-Newton} and \textit{NuSTAR} observations of the `bare' narrow line Seyfert 1 Ton S180 ($z=0.062$), carried out in 2016 and providing the first hard X-ray view of this luminous galaxy. We find that the 0.4--30…
We first present a short overview of X-ray probes of the black hole region of active galaxies (AGN) and then concentrate on the X-ray search for supermassive black holes (SMBHs) in optically non-active galaxies. The first part focuses on…
Narrow-line Seyfert 1 galaxies are identified by their uniform optical spectral properties. Studies of samples of NLS1s reveal, however, a range of X-ray spectral and variability behavior, and UV spectral behavior. We describe the range of…
We review observations and theoretical models of X-ray/gamma-ray spectra of radio-quiet Seyfert galaxies and of Galactic black-hole candidates (in the hard spectral state). The observed spectra share all their basic components: an…
Selected topics dealing with X-ray/soft gamma-ray emission from accreting black-hole sources are reviewed. The shape of soft gamma-ray spectra of Seyferts observed by OSSE can be well modelled by thermal Comptonization. A very strong…
Using new XMM-Newton observations we detect hard X-ray time lags in the rapid variability of the Compton-thin Seyfert 2 galaxy IRAS 18325-5926. The higher-energy X-ray variations lag behind correlated lower-energy variations by up to ~3ks…
Rapid flux changes in the X-ray emission from active galactic nuclei are commonly observed. The power-density spectra show a pseudo power-law form with a turnover at low frequencies and a high frequency break, similar to galactic black-hole…
Most ultraluminous X-ray sources (ULXs) are thought to be powered by neutron stars and black holes accreting beyond the Eddington limit. If the compact object is a black hole or a neutron star with a magnetic field $\lesssim10^{12}$ G, the…
In the last few years, a few supermassive black holes (SMBHs) have shown short-term (of the order of hours) X-ray variability. Given the limited size of the sample, every new addition to this class of SMBHs can bring invaluable information.…
We report the results of XMM-Newton observations of Sgr A*, the radiative counterpart of the massive black hole at the nucleus of our Galaxy, performed in the frame of the guaranteed time survey program of the Galactic Center region. The…
We present a spectral analysis of the NuSTAR and XMM-Newton observations of the Seyfert 1h galaxy/ULIRG IRAS 05189-2524 taken in 2013. We find evidence for relativistic disk reflection in the broadband X-ray spectrum: a highly asymmetric…
Supergiant Fast X-ray Transients are a class of Galactic High Mass X-ray Binaries with supergiant companions. Their extreme transient X-ray flaring activity was unveiled thanks to INTEGRAL/IBIS observations. The SFXTs dynamic range, with…
We propose that the X--ray emission from radio quiet AGN and galactic black holes is due to Comptonization of soft thermal photons emitted by the underlying accretion disk in localized structures (blobs). The power per unit area produced by…
We report on a long (100 ks) XMM-Newton observation of the bright Seyfert 1 galaxy Arakelian 120. The source previously showed no signs of intrinsic reddening in its infrared-ultraviolet continuum and previous observations had shown no…
Variability across the electromagnetic spectrum is a property of AGN that can help constraining the physical properties of these galaxies. This is the third of a serie of papers with the aim of studying the X-ray variability of different…
We present the results of concurrent X-ray and optical monitoring of the Seyfert 1 galaxy Mrk 79 over a period of more than five years. We find that on short to medium time-scales (days to a few tens of days) the 2-10 keV X-ray and optical…
Matter flows in the central regions of quasars during their active phases are probably responsible for the properties of the super-massive black holes and that of the bulges of host galaxies. To understand how this mechanism works, we need…
X-ray binaries are known to show state transitions related to accretion rate changes which are often accompanied with dramatic changes in the jet emission. However, it is not clear whether this characteristics of stellar-mass black hole…
X-ray spectra of Seyfert galaxies have revealed a new type of X-ray spectral feature, one which appears to offer important new insight into the black hole system. XMM/Chandra revealed several narrow emission lines redward of Fe Kalpha in…
Narrow-line Seyfert 1 galaxies (NLS1s) is one of the few classes of active galactic nuclei (AGN) harboring powerful relativistic jets and detected in $\gamma$ rays. NLS1s are well-known X-ray sources. While in non-jetted sources the origin…