Related papers: X-ray dependencies on luminosity in AGN
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…
The majority of Active Galactic Nuclei (AGN) observed by XMM-Newton reveal narrow Fe K-alpha lines at ~ 6.4 keV, due to emission from cold (neutral) material. There is an X-ray Baldwin effect in Type I AGN, in that the equivalent width of…
We present evidence for changes in the strength and profile of the iron K-alpha line in Active Galactic Nuclei (AGN), based on X-ray observations with ASCA. There is a clear decrease in the strength of the line with increasing luminosity.…
Most Active Galactic Nuclei (AGN) exhibit a narrow Fe Kalpha line at ~ 6.4 keV in the X-ray spectra, due to the fluorescent emission from cold material far from the inner accretion disk. Using XMM-Newton observations, Page et al. found that…
We report on a detailed analysis of the correlation between the optical-UV (Lo) and X-ray (Lx) luminosities of quasars by means of Monte Carlo simulations, using a realistic luminosity function. We find, for a quasar population with an…
The broadband X-ray spectra of AGNs contains information about the nuclear environment from Schwarzschild radii scales to distances of ~1 pc. In addition, the average shape of the X-ray spectrum is an important input into X-ray background…
Chandra and XMM surveys show that the fraction of obscured AGN decreases rapidly with increasing luminosity. Although this is usually explained by assuming that the covering factor of the central engine is much smaller at luminous QSOs, the…
Some progress in understanding AGN variability is reviewed. Reprocessing of X-ray radiation to produce significant amounts of longer-wavelength continua seems to be ruled out. In some objects where there has been correlated X-ray and…
We investigated the relationship between the X-ray variability amplitude and X-ray luminosity for a sample of 14 bright Ultra-luminous X-ray sources (ULXs) with XMM-Newton/EPIC data, and compare it with the well established similar…
In this proceedings paper, I overview the current status of the X-ray luminosity function of AGNs in the soft (0.5-2 keV) band, extended using XMM-Newton and Chandra survey data. We found that the number density of low luminosity AGNs peaks…
X-ray variability is a well-established characteristic of active galactic nuclei (AGN), known to correlate inversely with both the supermassive black hole mass and luminosity, although the degree of each remains a topic of debate. The…
The existence of an anti-correlation between the equivalent width (EW) of the narrow core of the iron Kalpha line and the luminosity of the continuum (i.e. the X-ray Baldwin effect) in type-I active galactic nuclei has been confirmed over…
Using Chandra High Energy Grating (HEG) observations of 32 AGNs, we present a systematic study of the X-ray Baldwin effect (XBE, i.e. the anti-correlation between narrow Fe K{\alpha} line EW and X-ray continuum luminosity for AGN samples)…
X-ray spectra of active galactic nuclei (AGN) are usually described as power law spectra, characterized by the spectral slope $\alpha$ or photon index $\Gamma$. Here we discuss the X-ray spectral properties within the framework of clumpy…
Long-time-scale X-ray and optical variability is a key characteristic of AGN. Here, we summarise our current understanding of the X-ray and optical continuum variability of radio-quiet AGN and the relation between the two bands. We…
The observed relation between the soft X-ray and the optical-ultraviolet emission in active galactic nuclei (AGN) is non-linear and it is usually parametrized as a dependence between the logarithm of the monochromatic luminosity at 2500…
We use highly spectroscopically complete deep and wide-area Chandra surveys to determine the cosmic evolution of hard X-ray-selected AGNs. We determine hard X-ray luminosity functions (HXLFs) for all spectral types and for broad-line AGNs…
We derive an X-ray luminosity function for active galactic nuclei (AGN) that accounts for the X-ray source counts in the 0.5-2.0 and 2-10 keV energy ranges, the redshift distribution of AGNs in the ROSAT Deep Survey (RDS), as well as the…
Low-luminosity AGN (with X-ray luminosity < 1e42 ergs/s) far outnumber ordinary AGN, and are therefore perhaps more relevant to our understanding of AGN phenomena and the relationship between AGN and host galaxies. Many normal galaxies…
The X-ray variability of the Active Galactic Nuclei (AGN) has been most often investigated with studies of individual, nearby, sources, and only a few ensemble analyses have been applied to large samples in wide ranges of luminosity and…