Related papers: Long-Term X-ray Spectral Variability in Seyfert 1 …
We report on the results of a three-year program of coordinated X-ray and optical monitoring of the narrow-line Seyfert 1 galaxy NGC 4051. The rapid continuum variations observed in the X-ray spectra are not detected in the optical,…
The nature of the obscuring material in active galactic nuclei (AGN) can be studied by measuring changes in the line-of-sight column density, $N_{\rm H,los}$, over time. This can be accomplished by monitoring AGN over long periods of time…
We present simultaneous observations by EUVE, ASCA, and RXTE of the type~1 Seyfert galaxy NGC 5548. These data indicate that variations in the EUV emission (at $\sim 0.2 $keV) appear to lead similar modulations in higher energy ($\ga 1…
We have characterized the energy-dependent X-ray variability properties of the Seyfert~1 galaxy NGC 3783 using archival XMM-Newton and Rossi X-ray Timing Explorer data. The high-frequency fluctuation power spectral density function (PSD)…
The bright, soft X-ray spectrum Seyfert 1 galaxies Ark 564 and Ton S180 were monitored for 35 days and 12 days with ASCA and RXTE (and EUVE for Ton S180). The short time scale (hours-days) variability patterns were very similar across…
We study the flux-flux plots (FFPs) of the Seyfert galaxy SWIFT J2127.4+5654 which was observed simultaneously by XMM-Newton and NuSTAR. The 0.7-2 keV FFPs show a non-linear behaviour, while they are well fitted by a straight line, in the…
NGC 4151 is the brightest Seyfert 1 nucleus in X-rays. It was the first object to show short time delays in the Fe K band, which were attributed to relativistic reverberation, providing a new tool for probing regions at the black hole…
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…
On 9-11 May 1998, the highly-variable, low luminosity Seyfert 1 galaxy NGC4051 was observed in an unusual low flux state by BeppoSAX (Guainazzi et al. 1998) RXTE and EUVE. We present fits of the 4-15 keV RXTE spectrum and BeppoSAX MECS…
We combine the long-term optical light curve of the Seyfert 1 galaxy NGC5548 with the X-ray light curve measured by the Rossi X-ray Timing Explorer over 6 years, to determine the relationship between the optical and X-ray continua. The…
We examine whether the spectral energy distribution of optical continuum emission of active galactic nuclei (AGNs) changes during flux variation, based on accurate and frequent monitoring observations of 11 nearby Seyfert galaxies and QSOs…
We have studied the long-term X-ray light curve (2$-$10 keV) of the luminous Seyfert 1 galaxy MCG-2-58-22 by compiling data, from various X-ray satellites, which together cover more than 20 years. We have found two distinct types of time…
A strong outburst in the X-ray continuum and a change of its Seyfert spectral type was detected in HE 1136-2304 in 2014. The spectral type changed from nearly Seyfert 2 type (1.95) to Seyfert 1.5 type in comparison to previous observations…
Aims: We used data from the 58 month long, continuous Swift/Burst Alert Telescope (BAT) observations of the five brightest Seyfert galaxies at hard X-rays, to study their flux and spectral variability in the 20-100 keV energy band. The…
The variability of optical FeII blends in NGC 4051 is examined from spectra extracted from the AGN Watch program.In our analysis, the FeII complex are subtracted and measured with the following results. Firstly, the FeII variations were…
We present the light curves obtained during an eight-year program of optical spectroscopic monitoring of nine Seyfert 1 galaxies: 3C 120, Akn 120, Mrk 79, Mrk 110, Mrk 335, Mrk 509, Mrk 590, Mrk 704, and Mrk 817. All objects show…
The unprecedented sensitivity of current X-ray telescopes allows for the first time to address the issue of the Fe K line complex variability patterns in bright, nearby AGNs. We examine XMM-Newton observations of the brightest sources of…
During 1997 March-July, XTE observed the bright, strongly variable Seyfert 1 galaxy NGC 3516 once every ~12.8 hr for 4.5 months and nearly continuously (with interruptions due to SAA passage but not Earth occultation) for a 4.2 day period…
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…
Results of a long-term spectral monitoring of the active galactic nucleus of NGC 4151 are presented (11 years, from 1996 to 2006). High quality spectra (S/N>50 in the continuum near Halpha and Hbeta) were obtained in the spectral range…