We present an occultation of the central X-ray emitting region in the Seyfert Galaxy NGC 1365. This extreme spectral variation (from Compton-thin to reflection-dominated and back to Compton-thin in four days) has been caught in a ten days Chandra monitoring campaign consisting of six short (15 ks) observations performed every two days. We discuss the implications of this occultation within the ...

We present Chandra observations of 18 spectroscopically selected quasars, already known to be X-ray weak from previous ROSAT observations. All the sources but one are detected by Chandra, and spectral analysis suggests that most of them are intrinsically underluminous in the X-rays (by a factor from 3 to > 100). These objects could represent a large population of quasars with a Spectral Energy ...

We have analysed the optical luminosity-redshift distribution properties of bright QSOs, using a new large sample from the Hamburg/ESO survey. The sample provides insight into the hitherto poorly sampled bright tail of the luminosity function, allowing to monitor its evolution with redshift up to z ≈ 3. The slope increases significantly towards higher z, inconsistent with the predictions of pur...

We present observations in the 0.1–100 keV spectral band of 8 Seyfert 2 galaxies, obtained by means of BeppoSAX. These sources were selected according to their [OIII] optical emission line flux, to avoid biases against obscuration on the pc scale. All sources were detected. All of them are weak X–ray emitters, and most of them are characterized by prominent iron lines at 6.4–7 keV (EW> 500 eV) ...

We present ∼ 3 resolution imaging of the z = 4.7 QSO BR1202-0725 at 900 μm from the Submillimeter Array. The two submillimeter continuum components are clearly resolved from each other, and the positions are consistent with previous lower frequency images. In addition, we detect [C II] line emission from the northern component. The ratio of [C II] to far-infrared luminosity is 0.04% for the nor...

We have surveyed an optical/IR selected sample of nearby E/S0 galaxies with and without nuclear dust structures with the VLA at 3.6 cm to a sensitivity of 100 μJy. We can construct a Radio Luminosity Function (RLF) of these galaxies to ∼ 10 W Hz and find that ∼ 50% of these galaxies have AGNs at this level. The space density of these AGNs equals that of starburst galaxies at this luminosity. Se...

The continuum variability of optically selected Active Galactic Nuclei (AGN) is found to be consistent with that expected from a simple Poissonian process, in which the total luminosity of an object is produced by the multiple superposition of identical pulses. The energies, time-scales and rates of the pulses are found to be in the range of those expected from supernovae which generate fast ev...

We have discovered a very radio-loud Narrow-Line Seyfert 1 candidate: PKS 2004-447. This Seyfert is consistent with the formal definition for NLS1s, although it does not have quite the same spectral features as some typical members of this subclass. Only ROSAT survey data is available at X-ray wavelengths, so it has not been possible to compare this source with other NLS1s at these wavelengths....

We show new radio data and a re-analysis of old data for the Narrow Line Seyfert 1 (NLSy1) galaxy RGB J0044+193. This galaxy has previously been suggested to be both radio loud, and highly variable in the radio. As most NLSy 1 galaxies are radio quiet, this was interpreted as possible evidence that this AGN's jet was beamed toward the observer. This object was probably never either radio loud a...

We search for highly–ionized gas near three AGN host galaxies using the Chandra low–energy transmission grating spectrograph. Strong absorption lines from such gas are seen at z = 0, most likely from one or more of the following components: (1) a Galactic corona, (2) the Local Group medium, and (3) an extended warm–hot intergalactic medium (WHIM) filament passing through our local overdensity. ...