Related papers: Ubiquitous column density variability in Seyfert 2…
We present a study of the variations in the absorbing column density of 25 X-ray defined Seyfert 2 galaxies, as inferred from hard X-ray observations, on timescales from months to several years. We show that a significant variation of N$_H$…
We use hard X-ray data for an "optimal" sample of Seyfert 2 galaxies to derive the distribution of the gaseous absorbing column densities among obscured active nuclei in the local Universe. Of all Seyfert 2 galaxies in the sample, 75% are…
We have analyzed two long BeppoSAX observations of the bright Seyfert galaxy NGC 4151, searching for short timescale (10-200 ksec) X-ray spectral variability. The light curve of a softness ratio, chosen as most sensitive to pinpoint changes…
We present a sample of 17 type 2 Seyfert galaxies which have an X-ray column density lower than 10^{22} cm^{-2}. The Compton thin nature of these sources is strongly suggested by isotropic indicators. We estimate the fraction of these…
We analyze 37 RXTE observations of the type 2 Seyfert galaxy Mrk348 obtained during a period of 14 months. We confirm the spectral variability previous reported by Smith et al., in the sense that thecolumn density decreases by a factor of…
We have used X-ray spectra to measure attenuating columns in a large sample of Seyfert galaxies. Over 30 of these sources have resolved radio jets, allowing the relative orientation of the nucleus and host galaxy to be constrained. We have…
We present RXTE monitoring observations of the Seyfert 2 galaxy Mrk 348 spanning a 6 month period. The time-averaged spectrum in the 3-20 keV band shows many features characteristic of a Compton-thin Seyfert 2 galaxy, namely a hard…
We have discovered a correlation between the X-ray absorbing column densities within Seyfert galaxies and the relative alignment between the central engines and their host galactic disks. This correlation carries several implications for…
Seyfert 1.8/1.9 are sources showing weak broad H-alpha components in their optical spectra. We aim at testing whether Seyfert 1.8/1.9 have similar properties at UV and X-ray wavelengths to Seyfert 2. We use the 15 Seyfert 1.8/1.9 in the…
We present the results of the analysis of the X-ray spectrum of the Seyfert 2 Mrk 348, observed by Suzaku and XMM-Newton. The overall spectrum of Mrk 348 can be described by a primary power law continuum seen through three layers of…
We present and discuss a "3-dimensional" diagnostic diagram for Seyfert2 galaxies obtained by means of X-ray and [OIII] data on a large sample of objects (reported in the Appendix). The diagram shows the Kalpha iron line equivalent width as…
We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the neutral intrinsic…
This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in the optical band introduces scatter into…
We report the Rossi X-ray Timing Explorer observations of the heavily absorbed Seyfert 2 galaxy NGC 4945, which confirm the large column density of the absorber, corresponding to the optical depth to Thomson scattering of about 2.4. The…
High resolution spectroscopic observations of Seyfert galaxies with Chandra and XMM-Newton allows us to study the detailed ionization and thermal structures of the X-ray absorbing/emitting material in the circumnuclear environment. The vast…
We have studied the correlation among X-ray absorption, optical reddening and nuclear dust morphology in Seyfert 2 galaxies. Two main conclusions emerge: a) the Balmer decrement and the amount of X-ray absorption are anticorrelated on a…
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…
Context. Obscuration events caused by outflowing clumps or streams of high column density, low ionisation gas, heavily absorbing the X-ray continuum, have been witnessed in a number of Seyfert galaxies. Aims. We report on the X-ray…
X-ray unabsorbed Seyfert 2 galaxies appear to have X-ray absorption column densities that are too low (NH < 10^22 cm-2) to explain the absence of broad emission lines in their optical spectra, challenging the standard AGN unification model.…
We have analyzed the two longest (elapsed time > 3 days) BeppoSAX observations of the X-ray brightest Seyfert galaxy, NGC 4151, to search for spectral variability on time-scales from a few tens of ksec to years. We found in both cases…