Related papers: Optical Continuum Variability of the Active Galaxy…
Changing-look active galactic nuclei (CL AGNs) show large changes in luminosity and optical spectral state on time-scales of a few years, and provide a valuable probe of time-dependent accretion in the disc-BLR-torus system. We present a…
We show that the time delay between the optical and X-ray outbursts of the black-hole soft X-ray transient source GRO J1655-40, observed in April 1996, requires that the accretion flow in this object must consist of two components: a cold…
We present up to two decades of spectroscopic monitoring of the double-peaked broad Halpha emission lines of seven broad-line radio galaxies. These extremely broad, double-peaked lines are successfully modeled by emission from gas in the…
We propose that changing-look AGN transitions arise from variations in the size of the inner ADAF disk. The AGN accretion disk consists of an outer thin disk and an inner thick ADAF component, whose size is intrinsically unstable and…
We report the results of WBVR photometry of the massive close x-ray binary V1341 Cyg=Cyg X-2 in 1986-1992. In the "off" state the amplitudes of the periodic component of light variations lie in the $0^{m}.265 - 0^{m}.278$ and $0^{m}.290 -…
To investigate further the comparison between AGN and black hole X-ray binaries, we have studied the main X-ray variability properties of the Seyfert 1 Galaxy Markarian 335. We put particular emphasis on the X-ray time lags, which is a…
Detailed line profile variability studies of the narrow line Seyfert 1 galaxy Mrk110 are presented. We obtained the spectra in a variability campaign carried out with the 9.2m Hobby-Eberly Telescope at McDonald Observatory. The integrated…
Context: Accretion onto galactic and supermassive black holes occurs in different modes, which are documented in hard and soft spectral states, commonly attributed to an advection-dominated flow (ADAF) inside a truncated disk and standard…
We present the results from a monitoring campaign of the Narrow-Line Seyfert~1 galaxy PG 1211+143. The object was monitored with ground-based facilities (UBVRI photometry; from February to July, 2007) and with Swift (X-ray…
We present the first results from a detailed analysis of a new, long ($\sim100$ ks) XMM-Newton observation of the narrow-line Seyfert 1 galaxy PG 1404$+$226 which showed a large-amplitude, rapid X-ray variability by a factor of $\sim7$ in…
The origin of the optical flux variability in active galactic nuclei (AGN) is largely unknown. Previous studies have correlated features of the variability structure function (SF) with AGN properties, though they mostly involved…
The observation of the Narrow-Line Seyfert 1 galaxy IRAS13349+2438 performed by XMM-Newton European Photon Imaging Camera between 0.3-10 keV, is presented here. The broadband spectrum of the source is dominated at low energies (E < 2 keV)…
We present a detailed analysis of the long-term photometric and spectroscopic evolution of V1180 Cas over a decade, aiming to identify the dominant mechanisms behind its variability. We combine multi-band light curves from 1999 to 2025 with…
We investigate the spectral variability of the Seyfert galaxy Fairall 9 using almost 6 years of monitoring with the Rossi X-ray Timing Explorer (RXTE) with an approximate time resolution of 4 days. We discover the existence of pronounced…
We analyze the photometric variability of 4,611 active galactic nuclei (AGNs) from the Sloan Digital Sky Survey Stripe 82. We recover the spectral energy distribution (SED) of the variable flux as a function of wavelength. For rest…
We present modeling and interpretation of the continuum and emission lines for a sample of 51 unobscured Type 1 active galactic nuclei (AGN). All of these AGNs have high quality spectra from both XMM-Newton and Sloan Digital Sky Survey…
Long-term (up to 10000d) monitoring has been undertaken for 41 Seyferts in the near-IR (JHKL). All but 2 showed variability, with K ampl in the range <0.1 to > 1.1 mags. The timescale for detectable change is from about one week to a few…
We explored a sample of 545 local galaxies using data from the 3XMM-DR7 and SDSS-DR8 surveys. We carried out all analyses up to z\,$\sim$\,0.2, and we studied the relation between X/O flux ratio and accretion rate for different classes of…
Six XMM-Newton observations of the bright narrow line Seyfert 1, Mrk 110, from 2004-2020, are presented. The analysis of the grating spectra from the Reflection Grating Spectrometer (RGS) reveals a broad component of the He-like Oxygen…
The dependence of the long-term optical/UV variability on the spectral and the fundamental physical parameters for radio-quiet active galactic nuclei (AGNs) is investigated. The multi-epoch repeated photometric scanning data in the…