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Aims. We study the X-ray power spectrum of active galactic nuclei (AGN) in order to investigate whether Seyfert I and II power spectra are similar or not and whether AGN variability depends on the mass and accretion rate of black holes as well as to compare the power spectra of AGN with the power spectra of Galactic X-ray black hole binaries. Method. We used 14–195 keV band light curves from the 157-month Swift/BAT hard X-ray survey, and we computed the mean power spectrum and excess variance of AGN in narrow black hole mass and AGN luminosity bins. We fitted a power-law model to the AGN power spectra, and we investigated whether the power spectrum parameters and the excess variance depend on the black hole mass, luminosity, and accretion rate of AGN. Results. We found the Seyfert I and Seyfert II power spectra to be identical, in agreement with AGN unification models. The mean AGN X-ray power spectrum has the same power-law like shape, with a slope of −1 in all AGN irrespective of their luminosity and black hole mass. We did not detect any flattening to a slope of zero at frequencies as low as 10−9 Hz. We detected an anti-correlation between the power spectral density function (PSD) amplitude and the accretion rate, similar to what has been seen in the past in the 2–10 keV band. This implies that the variability amplitude in AGN decreases with an increasing accretion rate. The universal AGN power spectrum is consistent with the mean 2–9 keV band Cyg X-1 power spectrum in its soft state. We detected a small difference in amplitude, but this is probably due to the difference in energy. Conclusions. The mean low-frequency AGN X-ray power spectrum is consistent with the extension of the mean 0.01–25 Hz Cyg X-1 power spectrum in its soft state to lower frequencies. We cannot prove that the mean AGN PSD is analogous to the mean Cyg X-1 PSD in its soft state, as we do not know the location of the high-frequency break in the hard X-ray AGN PSDs. However, if this is the case, then the accretion disc in AGN probably extends to the radius of the innermost circular stable orbit (as is probably the case with the black hole binaries in their soft state). The X-ray corona will then be located on top, illuminating the disc and producing the X-ray reflection and disc reverberation phenomena commonly observed in these objects. Furthermore, the agreement between the PSD amplitude in AGN and the Cyg X-1 (either in the soft or the hard state) over many decades in frequency indicates that the X-ray variability process is probably the same in all accreting objects, irrespective of the mass of the compact object. We plan to investigate this issue further in the near future. [ABSTRACT FROM AUTHOR]

We present a study of outburst activity in the BL Lacertae source OJ 287, which has been observed extensively with the X-ray telescope (XRT) on board the Neil Gehrels Swift Observatory. We demonstrate that the results of our analysis of X-ray flaring activity using the Swift/XRT data allow for the key characteristics of the OJ 287 secondary to be refined (its nature and mass). We discover that the energy spectra in all spectral states can be fitted using the XSPEC bulk motion Comptonization (BMC) model. As a result we find that the X-ray photon index of the BMC model, Γ, correlates with the mass accretion rate, Ṁ. We establish that Γ increases monotonically with Ṁ from the low-hard state, Γ ∼ 1.5, to the high-soft state, Γ ∼ 2.8, and finally saturates. The index behavior is similar to that in a number of black hole (BH) candidates in which we show that its saturation is observational evidence of the presence of a BH. Based on this correlation, we applied a scaling method and determine that a secondary BH mass in OJ 287 is about ∼1.25 × 108 solar masses, using the well-studied X-ray BH binaries XTE 1550–564, H 1743–322, 4U 1630–47, and GRS 1915+105 as well as extragalactic BHs ESO 243–49 and M101 ULX–1, as reference sources. Also, using the power spectrum analysis, we infer the size of the Compton cloud LCC ∼ 1013 cm where X-ray spectra were formed. Using this value of LCC, we confirm that a BH mass of the secondary in OJ 287 was on the order of 108 solar masses as we derived using the index, Γ–correlation (the scaling method) with respect of the mass accretion rate. [ABSTRACT FROM AUTHOR]

Here, we investigate the kinematics of the part of the broad-line region (BLR) in active galactic nuclei (AGNs) emitting H β and H α emission lines. We explore the widths and asymmetries of the broad H β and H α emission lines in a sample of high-quality (i.e. high signal-to-noise ratio) spectra of type-1 AGN taken from the Data Release 16 of the Sloan Digital Sky Survey in order to explore possible deviation from the gravitationally bound motion. To find only the broad component of H β and H α, we use the fantasy (Fully Automated pythoN Tool for AGN Spectra analYsis) code for the multicomponent modelling of the AGN spectra and for careful extraction of the broad emission-line parameters. We show that based on the broad-line profiles widths and asymmetries, the BLR gas emitting H β and H α lines follows similar kinematics, and seems to be virialized in our sample of type-1 AGN. [ABSTRACT FROM AUTHOR]

We analyse medium resolution optical spectra of 14 narrow-line Seyfert 1 galaxies with average to strong iron emission. The targets were observed several times over a 2-yr period to probe the nature of spectral variations. Parameters determined from fitting the line profiles include relative strength, width, and asymmetry. We explore the applicability of various profile combinations to H β. We achieve satisfactory fits using three components: the narrow and broad components characteristic of all Seyfert 1 galaxies and that are reasonably represented by Gaussian profiles, and an intermediate component with width similar to that of the Fe  ii lines. This intermediate component accounted for the largest fraction of the H β flux in most of our sample, especially when fitted with a Lorentzian instead of a Gaussian profile. This Lorentzian component improves the overall H β fits in most cases. In contrast to many other types of active galactic nucleus, no dramatic spectral changes were detected in our sample over the 2-yr period spanning this study, even though some of our targets are known for large and rapid X-ray variability. In particular, we find the variability of the Fe  ii lines relative to the H β intermediate component to be minimal. For the [O  iii ] lines, we identified asymmetries in almost all our targets well represented by two Gaussians: a primary central and a second blueshifted component. These may signify different gas dynamics connected with nuclear outflow. As in several previous studies, we identify a clear correlation between [O  iii ] asymmetry and its core component width. [ABSTRACT FROM AUTHOR]