Related papers: Rapid N_H Changes in NGC 4151
We present the variability analysis of a 100 ks XMM-Newton observation of the Seyfert 1.5 active galaxy NGC 3227. The observation found NGC 3227 in a period where its hard power-law component displayed remarkably little long-term…
We present results from a half-day observation by XMM-Newton of the nucleus of the nearby Seyfert 2 galaxy NGC 6300. The X-ray spectrum of the nucleus consists of a heavily absorbed hard component dominating the 3--10 keV band and a soft…
The ISO-SWS infrared spectroscopic observations of the nucleus of Seyfert galaxy NGC4151, which are described in a companion paper, are used together with a compilation of UV to IR narrow emission line data to determine the spectral shape…
We present results from RXTE data obtained during a systematic monitoring program of four Seyfert galaxies (NGC5548, NGC5506, MCG-6-30-15 and NGC4051). We studied the variability of three hardness ratios derived from the light curves in…
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 present the first high-resolution X-ray spectrum of the Seyfert 1.5 galaxy NGC 4151. Observations with the Chandra High Energy Transmission Grating Spectrometer reveal a spectrum dominated by narrow emission lines from a spatially…
We present new results from a Chandra HETG observation of NGC 5548 and give a comparison of absorption and emission features found in other Seyfert 1 galaxies using Chandra grating observations. Deep soft X-ray edges are seen in Mkn 509 and…
Using The Hubble Space Telescope's Space Telescope Imaging Spectrograph HST's STIS, observations of the OIII emission from the narrow-line region (NLR) of NGC 4151 were obtained and radial velocities determined. Five orbits of HST time were…
Results from BeppoSAX observations of Compton--thick Seyfert 2 galaxies are summarized and reviewed, and their general properties derived and discussed. In five out of the seven observed sources, the nucleus is directly visible at high…
The X-ray spectra of two intermediate type Seyfert galaxies are investigated using ASCA observations separated by more than a year. Both NGC 4388 and ESO 103-G35 exhibit strong, narrow Fe K alpha line emission and absorption by cold neutral…
We present a Chandra monitoring campaign of the highly variable Seyfert galaxy UGC 4203 (the "Phoenix Galaxy") which revealed variations in the X-ray absorbing column density on time scales of two weeks. This is the third, clear case, after…
We present the temporal analysis of X-ray observations of the radio-loud Narrow-Line Seyfert 1 galaxy (NLS1) PKS 0558-504 obtained during the XMM-Newton Calibration and Performance Verification (Cal/PV) phase. The long term light curve is…
We present results from a joint Xmm-Newton/NuSTAR monitoring of the Seyfert 1 NGC 4593, consisting of 5x20 ks simultaneous observations spaced by two days, performed in January 2015. The source is variable, both in flux and spectral shape,…
We use a model-independent technique to investigate the nature of the 2-15 keV X-ray spectral variability in four Seyfert galaxies and distinguish between spectral pivoting and the two-component model for spectral variability. Our analysis…
We report optical, radio and X-ray observations of the Narrow-Line Seyfert 1 galaxy RX J1702.5+3247. The soft (0.1-2 keV) X-ray flux, measured by BeppoSAX, is characterized by strong variability on short time scales (< 500 sec). The most…
Warm absorbers are an important new tool for investigating the conditions within the central regions of active galaxies. They have been observed in ~50% of the well-studied Seyfert galaxies and have also been detected in quite a number of…
ASCA observations of the Seyfert 2 galaxy NGC 7582 revealed it was highly variable on the timescale of $\sim2\times10^4$ s in the hard X-ray (2-10 keV) band, while the soft X-ray (0.5-2 keV) flux remained constant during the observations.…
NGC 7582 is a well-studied X-ray bright Seyfert 2 with moderately heavy ($N_{\text{H}}\sim10^{23}-10^{24}$~cm$^{-2}$), highly variable absorption and strong reflection spectral features. The spectral shape changed around the year 2000,…
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 present H- and K-band data from the inner arcsecond of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive optics assisted near-infrared imaging field spectrograph OSIRIS at the Keck Observatory. We present the morphology and…