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Previous studies have identified the Fundamental Plane (FP) of Active Galactic Nuclei (AGNs) in recent years. However, these findings relied on total black hole mass, also known as dynamical mass, (Mdyn). Instead the fundamental plane may be governed by BH spin. In this study, we take the black hole spin-mass energy ( M spin ) as a new variable, which is closely related to the supermassive black hole (SMBH). We collected a sample of 62 flat-spectrum radio quasars (FSRQs) with gamma-ray luminosity ( L γ ), X-ray luminosity ( L X ) and spin-mass energy ( M spin ) to construct a new fundamental plane of blazars. Our analysis demonstrates that the fundamental plane (log L γ = 0.662 + 0.193 − 0.193 log L X + 0.495 + 0.154 − 0.154 log M spin + 14.579 + 7.140 − 7.140 with R-Square = 0.783) has a stronger correlation with spin-mass energy ( M spin ) compared to the black hole mass. Therefore, M spin should be considered as an essential variable for the fundamental plane of blazars. Our findings may improve the understanding of the Blandford-Znajek process in FSRQs. [ABSTRACT FROM AUTHOR]

The radio quasar NVSS J141922−083830 (J1419−0838) was initially classified as an uncategorised blazar-type object, following its detection in the γ -ray band with the Fermi space telescope. Later, using multi-waveband observations and modeling, its was found to be a flat-spectrum radio quasar (FSRQ). However, its radio emission has never been discussed in depth in the literature. Here we present a detailed analysis on the radio properties of J1419−0838 using archival interferometric imaging data at pc and kpc scales. We conclude that the flux density variations, the flat radio spectrum, the compact nature of the quasar structure at all scales, and the relativistic Doppler enhancement of the radio emission all support the previous classification as an FSRQ. We also investigated the short- and long-term mid-infrared (MIR) light curve of the quasar based on observations by the Wide-field Infrared Survey Explorer satellite, and found that there is significant variability on time-scales of days as well as years. Comparison of the MIR light curve to the times of previously reported γ -ray and optical flares shows no clear correlation between the events at different wavebands. [ABSTRACT FROM AUTHOR]

As Setti and Woltjer noted back in 1973, one can use quasars to construct the Hubble diagram; however, the actual application of the idea was not that straightforward. It took years to implement the proposition successfully. Most ways to employ quasars for cosmology now require an advanced understanding of their structure, step by step. We briefly review this progress, with unavoidable personal biases, and concentrate on bright unobscured sources. We will mention the problem of the gas flow character close to the innermost stable circular orbit near the black hole, as discussed five decades ago. This problem later led to the development of the slim disk scenario and is recently revived in the context of Magnetically Arrested Disks (MAD) and Standard and Normal Evolution (SANE) models. We also discuss the hot or warm corona issue, which is still under debate and complicates the analysis of X-ray reflection. We present the scenario of the formation of the low ionization part of the Broad Line Region as a failed wind powered by radiation pressure acting on dust (Failed Radiatively Driven Dusty Outflow – FRADO). Next, we examine the cosmological constraints currently achievable with quasars, primarily concentrating on light echo methods (continuum time delays and spectral-line time delays to the continuum) that are (or should be) incorporating the progress mentioned above. Finally, we briefly discuss prospects in this lively subject area. [ABSTRACT FROM AUTHOR]

Magnetic monopoles have been a trending topic among physicists and astronomers since the 1930s. Researchers have been working hard to find evidence of magnetic monopoles in laboratories. The existence of magnetic monopoles can rationally explain the stability of charges, the quantization of charges, the structure of leptons, the unified composition of leptons and hadrons, and the symmetry of leptons and quarks. The presence of these mysterious particles in the universe could have significant implications for theoretical physics and astrophysics. The Grand Unified Theory has also predicted the existence of magnetic monopoles, which is interestingly implied by some astronomical observations. Noticing that the growth of supermassive black holes in the early universe is an increasingly challenging difficulty faced by astronomers, here we argue that it could be solved with the help of magnetic monopoles. As suggested by Peng et al. in A Monopole Model for Galactic Nuclei. In: Structure and Evolution of Active Galactic Nuclei, vol. 121, p. 663 (1986), quasars containing magnetic monopoles at the center can continuously catalyze the decay of protons to release energy. We examine this model by using quasar data from the Sloan digital sky survey. It is shown that the initial mass distribution of quasars derived from the magnetic monopole model exhibits a Gaussian distribution. At the same time, the initial mass function is also slightly higher than previously expected, which could be verified by future observations. [ABSTRACT FROM AUTHOR]

Probing the physics of the accretion flow around active galactic nuclei (AGN) is crucial to understanding their emission mechanisms as well as being able to constrain the geometrical and variability properties of the different regions around them. The soft X-ray excess – usually observed below ∼ 2 keV in excess of the dominant X-ray powerlaw continuum – is one prominent feature that is commonly seen in type 1 Seyfert AGN and therefore readily provides a useful diagnostic of the accretion flow mechanism around these systems. NGC 5940 is a Seyfert 1 AGN which reveals strong, prominent soft X-ray excess below ∼ 2 keV as seen in both its XMM-Newton and Swift observations. Model fit to the data revealed that this feature could be equally well explained by the ionised partial covering, the thermal Comptonisation and the blurred reflection models. Although the other models cannot be decisively ruled out with the data at hand, the lack of significant broad iron K α as well as any significant emission/absorption line features in the reflection grating spectrometer (RGS) data tend to favour the thermal Comptonisation origin for the soft X-ray excess in NGC 5940. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "The fundamental plane of FSRQs based on the black hole spin-mass energy." The correction addresses incorrect references in the original article and provides the correct citations. It clarifies that the citations of Xiao et al. (2023) should have been citations of Zhu et al. (2023). Additionally, it corrects the citation of Blandford and Koenigl (1979) to Blandford and Levinson (1995). The correction also removes a duplicate citation of McClintock et al. (2014) in the last paragraph of section 1. The original article has been corrected. [Extracted from the article]

In this paper, we use the distributions of two-component radio emissions to investigate the consequences of relativistic beaming on the unified scheme of blazar populations and radio galaxies. Our results show remarkable continuity in the distributions of source luminosities (radio core and extended luminosities, L C and L E respectively as well as γ -ray luminosity L γ ) from radio galaxies at low luminosities to FSRQs at high luminosities through BL subclasses as expected in the blazar unification scheme in a sense suggesting that the sequence of BL Lacs, FSRQs and radio galaxies represents progressively misaligned populations of AGNs. Distribution of radio core-dominance is consistent with average projection angles of 13.5∘, 14.8∘, 16.8∘, 20.4∘ and 28.2∘ for ISPs, LSPs, FSRQs, HSPs, and radio galaxies, respectively. Linear regression analyses of our data yield significant anti-correlation (r > 0.60 ) between core-dominance parameter (C ) and L E in each individual subsample: the correlation is significant only when individual subsamples are considered. There is a systematic sequence of the distribution of the different subclasses on the C − L E plane. Nevertheless, little or no correlation between C and L C or between C and L γ (r < 0.50 ) was observed. There is a clear dichotomy between high synchrotron-peaking BL Lacs and other BL Lac subclasses. The results are consistent with a unified view for blazars and can be understood in terms of relativistic beaming persisting at largest scales. [ABSTRACT FROM AUTHOR]

We remind that the "ring down" features observed in the LIGO gravitational waves (GW) resulted from trembling of "photon spheres" ( R photon = 3 M , by using units G = c = 1 ) of newly formed compact objects and not from the trembling of their event horizons (EH) R = 2 M (Cardoso et al. 2016). Further, the tentative evidence for late time "echoes" in GWs might be signatures of horizonless compact objects rather than vacuum black holes (BHs) possessing EHs. In general, in the past, many authors have considered the possibility that the so-called BHs might be only BH mimickers (BHMs) having physical surfaces (R ≈ 2 M ). Similarly, even for an ideal BH, the radius of its shadow, which is R shadow = 3 R photon , is actually the gravitationally lensed shadow of its photon sphere. Accordingly, any compact object having R ≤ R photon = 3 M would generate similar shadow. Thus, no observation has ever detected any EH (any exact BH). Also, by definition, it is fundamentally impossible to directly detect any EH (Abramowicz et al. 2002). One notes that all astrophysical compact objects, except exact (chargeless) BHs, possess intrinsic magnetic moment that is dominated by the dipole component. Even rapidly spinning neutron stars (NS) are treated as spinning magnetic dipoles by ignoring the weak additional multipole moments. Hence, since an exact BH has no magnetic moment, a collapsing massive star must radiate away its multipole magnetic moments one by one and left with mostly the dipole moment immediately before becoming a BH (Ginzburg 1964). One also notes that the magnetic field embedded in the accreting plasma close to the compact object is expected to have a radial pattern of B ∼ r − 1 , while the stronger BHM dipole magnetic field should fall off as B ∼ r − 3 . Accordingly, it has been suggested that one may try to infer the true nature of the so-called astrophysical BHs by studying the radial pattern of the magnetic field in their vicinity (Lobanov 2017). But here we highlight that, close to the surface of BHMs, the magnetic field pattern differs significantly from the same for non-relativistic dipoles. In particular, we point out that, for ultra-compact BHMs, the polar field is weaker than the equatorial field by an extremely large factor of ∼ z s ln z s , where z s ≫ 1 is the surface gravitational redshift. We suggest that, by studying the radial variation as well as significant angular asymmetry of magnetic field structure near the compact object, future observations might differentiate a theoretical BH from a astrophysical BHM. This study also shows that even if some BHMs would be hypothesized to possess magnetic fields even stronger than that of magnetars. In certain cases, they may effectively behave as atoll type neutron stars possessing extremely low magnetic fields. [ABSTRACT FROM AUTHOR]

In this paper, the average energy of the $\gamma$ -photon ( $E_{\mathrm {a},\mathrm{ph}}$ ) is calculated and the correlation between $\log E_{\mathrm{a},\mathrm{ph}}$ and the logarithm of the synchrotron peak frequency ( $\log\nu_{\mathrm{p}}$ ) is discussed for a sample of 620 BL Lac objects. The results show that there exists a positive correlation between the $\gamma$ -photon energy and the synchrotron peak frequency for BL Lac objects, which implies that the $\gamma$ -ray emissions are related to the low-energy emissions of radio to X-ray bands, and the high energetic $\gamma$ -ray emissions are only partially from the synchrotron self-Compton process (SSC) for BL Lac objects. [ABSTRACT FROM AUTHOR]

We determined the spin value of supermassive black hole (SMBH) in active galactic nuclei (AGN) with investigated ultraviolet-to-optical spectral energy distribution, presented in the sample of Shang et al. (Astrophys. J. 619:41, 2005). The estimates of the spin values have been produced at the base of the standard geometrically thin accretion disk model using the results of the polarimetric observations. The polarimetric observations are very important for determining the inclination angle of AGN disk. We presented the results of our determinations of the radiation efficiency of the accretion flow and values of the spins of SMBHs, that derives the coefficient of radiation efficiency. The majority of SMBHs of AGNs from Shang et al. (Astrophys. J. 619:41, 2005) sample are to be the Kerr black holes with the high spin value. [ABSTRACT FROM AUTHOR]

We present the results based on the monitoring of the high energy peaked BL Lacertae object 1ES 2344+514 with the satellite Swift during 2005-2015. Our timing study shows that the source was highly variable on longer (weeks-to-months) time-scales with the 0.3-10 keV flux ranging by a factor of 13.3. The flux variability exhibited an erratic character, changing its amplitude and minimum flux level from flare to flare. In some epochs, an X-ray flare was accompanied by enhanced optical-UV activity, although the uncorrelated 0.3-10 keV and lower-frequency variabilities were also often seen. Our target was significantly passive on intra-day timescales compared to other HBLs. The logparabolic distribution of the X-ray emitting electrons and the underlying physical processes seem to be less important for this object in some epochs, since only seven out of the relatively rich spectra showed a curvature, while the majority of the 0.3-10 keV spectra fitted with a simple powerlaw well. The photon index varied on diverse timescales, and the source showed mainly a 'harder-when-brighter' spectral evolution. In the hardness ratio-flux plane, 1ES 2344+514 showed both clockwise and counterclockwise loops, indicating a complex spectral evolution with the flux. [ABSTRACT FROM AUTHOR]

Recent general relativistic simulations have shown that the coalescence of two spinning black holes (BH) can lead to recoiling speeds of the BH remnant of up to thousands of km/s as a result of the gravitational radiation emission. It is important that the accretion disc remains bound to ejected BH within the region where the gas orbital velocity is larger than the ejection speed. We considered the situation when the recoiling kick radius coincides with the radius of the broad line region (BLR). We show that in this situation the observed polarization data of accretion disk emission allow to determine the value of the recoil velocity. We present the estimates of the kick velocity for AGN with determined polarization data. [ABSTRACT FROM AUTHOR]

$\mathrm{[OIII]}\lambda 5007$ 'blue outliers'-that are suggestive of outflows in the narrow line region of quasars-appear to be much more common at intermediate $z$ (high luminosity) than at low $z$. About $40~\%$ of quasars in a Hamburg ESO intermediate $z$ sample of 52 sources qualify as 'blue outliers' (i.e., quasars with $\mbox{[OIII]}\lambda\lambda 4959,5007$ lines showing large systematic blueshifts with respect to rest frame). We discuss major findings on what has become an intriguing field in active galactic nuclei research and stress the relevance of 'blue outliers' to feedback and host galaxy evolution. [ABSTRACT FROM AUTHOR]

We study the velocity dispersion profiles of the nuclei of NGC 1326, 2685, 5273 and 5838 in the CO first overtone band. There is evidence for a black hole (BH) in NGC 1326 and 5838. Gas is seen flowing out of the nuclear region of NGC 5273. We put upper limits on the nuclear BHs responsible for its activity and that of NGC 2685. [ABSTRACT FROM AUTHOR]

The UV spectral range (1100-3000 Å) contains the strongest resonance lines observed in active galactic nuclei (AGN). Analysis of UV line intensity ratios and profile shapes in quasar spectra provide diagnostics of physical and dynamical conditions in the broad line emitting region. This paper discusses properties of UV lines in type-1 AGN spectra, and how they lead an estimate of ionizing photon flux, chemical abundances, radius of the broad line emitting region and central black hole mass. These estimates are meaningfully contextualised through the 4D 'eigenvector-1' (4DE1) formalism. [ABSTRACT FROM AUTHOR]

CUBES is a high-efficiency, medium-resolution ( R∼20,000) ground based UV (300-400 nm) spectrograph, to be installed in the cassegrain focus of one of ESO's VLT unit telescopes in 2017/18. The CUBES project is a joint venture between ESO and IAG/USP, and LNA/MCTI. CUBES will provide access to a wealth of new and relevant information for stellar as well as extragalactic sources. Main science cases include the study of beryllium and heavy elements in metal-poor stars, the direct determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range, as well as the study of active galactic nuclei and the quasar absorption lines. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive detectors, it will give a significant gain in sensitivity over existing ground based medium-high resolution spectrographs, enabling vastly increased sample sizes accessible to the astronomical community. We present here a brief overview of the project including the status, science cases and a discussion of the design options. [ABSTRACT FROM AUTHOR]

We develop the method that allows to estimate ultra high energy cosmic ray (UHECR) production in active galactic nuclei (AGNs). We used the model developed by Neronov et al. (New J. Phys. 11:065015, ) and estimated the magnetic field strength near the innermost stable orbit in an accretion disk and at the horizon radius of a supermassive black hole (SMBH) using the data of polarimetric observations of broad lines emission. It allows to estimate the kinetic power of the relativistic jet at the base of Blandford-Znajek mechanism. In a result we estimated the cosmic ray power for a number of AGNs with known values of SMBH spins. [ABSTRACT FROM AUTHOR]

Astronomical or cosmological redshifts are an observable property of extragalactic objects and have historically been wholly attributed to the recessional velocity of that object. The question of other, or intrinsic, components of the redshift has been highly controversial since it was first proposed. This paper investigates one theoretical source of intrinsic redshift that has been identified. The highly ionized regions of Active Galactic Nuclei (AGN) and Quasi-Stellar Objects (QSO) are, by definition, plasmas. All plasmas have electromagnetic scattering characteristics that could contribute to the observed redshift. To investigate this possibility, one region of a generalized AGN was selected, the so called Broad Line Region (BLR). Even though unresolvable with current instrumentation, physical estimates of this region have been published for years in the astronomical literature. These data, selected and then averaged, are used to construct an overall model that is consistent with the published data to within an order of magnitude. The model is then subjected to a theoretical scattering investigation. The results suggest that intrinsic redshifts, derivable from the characteristics of the ambient plasma, may indeed contribute to the overall observed redshift of these objects. [ABSTRACT FROM AUTHOR]

BL Lac object AO 0235+164 is a well-known object. We collect a large number of effective observation in B, V, R and I band from historical literatures. The possible periods are analyzed by means of discrete correlation function (DCF) method, structure function (SF) method and Jurkevich (J-K) method. The results show that there are possible periodic variations of 2.63-2.66 years in B band, 2.79-2.84 years in V band, 2.57-2.87 years in R band, 2.62-2.88 years in I band, respectively. [ABSTRACT FROM AUTHOR]

We compute the ultra-high energy (UHE) neutrino fluxes from plausible accreting supermassive black holes closely linking to the 377 active galactic nuclei (AGNs). They have well-determined black hole masses collected from the literature. The neutrinos are produced via simple or modified URCA processes, even after the neutrino trapping, in superdense proto-matter medium. The resulting fluxes are ranging from: (1) (quark reactions)- $J^{q}_{\nu\varepsilon}/(\varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1})\simeq8.29\times 10^{-16}$ to 3.18×10, with the average $\overline{J}^{q}_{\nu\varepsilon}\simeq5.53\times 10^{-10}\varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1}$, where ε∼10 is the opening parameter; (2) (pionic reactions)- $J^{\pi}_{\nu\varepsilon} \simeq0.112J^{q}_{\nu\varepsilon}$, with the average $J^{\pi}_{\nu\varepsilon} \simeq3.66\times 10^{-11}\varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1}$; and (3) (modified URCA processes)- $J^{URCA}_{\nu\varepsilon}\simeq7.39\times10^{-11} J^{q}_{\nu\varepsilon}$, with the average $\overline{J}^{URCA}_{\nu\varepsilon} \simeq2.41\times10^{-20} \varepsilon_{d}\ \mathrm{erg}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}\,\mathrm{sr}^{-1}$. We conclude that the AGNs are favored as promising pure neutrino sources, because the computed neutrino fluxes are highly beamed along the plane of accretion disk, peaked at high energies and collimated in smaller opening angle θ∼ ε. [ABSTRACT FROM AUTHOR]

Considering the host galaxy contribution, a spectral decomposition method is used to reanalyzed the archive data of optical spectra for a narrow line Seyfert 1 galaxy, NGC 4051. The light curves of the continuum f(5100 Å), and H β, He ii, Fe ii emission lines are given. We find strong flux correlations between line emissions of H β, He ii, Fe ii and the continuum f(5100 Å). These low-ionization lines (H β, Fe ii, He ii) have 'inverse' intrinsic Baldwin effects. Using the methods of the cross-correlation function and the Monte Carlo simulation, we find the time delays, with respect to the continuum, are $3.45^{+12.0}_{-0.5}~\mbox{days}$ with the probability of 34 % for the intermediate component of H β, $6.45^{+13.0}_{-1.0}~\mbox{days}$ with the probability of 65 % for the intermediate component of He ii. From these intermediate components of H β and He ii, the calculated central black hole masses are $0.86^{+4.35}_{-0.33}\times 10^{6}$ and $0.82^{+3.12}_{-0.45}\times 10^{6}~M_{\odot }$. We also find that the time delays for Fe ii are $9.7^{+3.0}_{-5.0}~\mbox{days}$ with the probability of 36 %, $8.45^{+1.0}_{-2.0}~\mbox{days}$ with the probability of 18 % for the total epochs and 'subset 1' data, respectively. It seems that the Fe ii emission region is outside of the H β emission region. [ABSTRACT FROM AUTHOR]

Using γ-ray data detected by Fermi Large Area Telescope (LAT) and multi-wave band data for 40 TeV active galactic nuclei (AGNs), we have studied the correlations between flux densities ( F, F, F, F and F) in the radio, infrared, optical, X-ray and γ-ray wave bands. Our results are the following: (1) For TeV HSP BL Lacertae objects (THBLs), there are strong correlations between F and F and between F and F in all states (average/high/low); (2) The TeV radio galaxies (TRGs) deviate from the area occupied by THBLs; (3) The TeV flat-spectrum radio quasars (TFSRQs) have much stronger γ-ray emission than THBLs; (4) For THBLs, there are weak correlations between F and F in all states as well as between F and F in both average and high states, and a strong correlation between F and F in the low state; (5) For THBLs, there are strong correlations between F and F in both low and average states as well as between F and F in all states and between F and F in all states, but no strong correlations among other bands are found. From these results, we suggest that for THBLs, the synchrotron self-Compton radiation (SSC) is the main mechanism of high energy γ-ray emission and the inverse Compton scattering of circum-nuclear dust is likely to be a important complementary mechanism. Compared with THBLs, TRGs and TFSRQs may have a different origin of high energy γ-ray. [ABSTRACT FROM AUTHOR]

The presence of convective and turbulent motions, and the evolution of magnetic fields give rise to existence of temperature fluctuations in stellar atmospheres, active galactic nuclei and other cosmic objects. We observe the time and surface averaged radiation fluxes from these objects. These fluxes depend on both the mean temperature and averaged temperature fluctuations. The usual photosphere models do not take into account the temperature fluctuations and use only the distribution of the mean temperature into surface layers of stars. We investigate how the temperature fluctuations change the spectra in continuum assuming that the degree of fluctuations (the ratio of mean temperature fluctuation to the mean temperature) is small. We suggest the procedure of calculation of continuum spectra, which takes into account the temperature fluctuations. As a first step one uses the usual model of a photosphere without fluctuations. The observed spectrum is presented as a part depending on mean temperature and the additional part proportional to quadratic value of fluctuation degree. It is shown that for some forms of absorption factor the additional part in Wien's region of spectrum can be evaluated directly from observed spectrum. This part depends on the first and second wavelength derivatives, which can be calculated numerically from the observed spectrum. Our estimates show that the temperature dependence of absorption factors is very important by calculation of continuum spectra corrections. As the examples we present the estimates for a few stars from Pulkovo spectrophotometric catalog and for the Sun. The influence of temperature fluctuations on color indices of observed cosmic objects is also investigated. [ABSTRACT FROM AUTHOR]

The possibility that BL Lac S5 0716+714 exhibits a linear root mean square (rms)-flux relation in its IntraDay Variability (IDV) is analysed. The results may be used as an argument in the existing debate regarding the source of optical IDV in Active Galactic Nuclei. 63 time series in different optical bands were used. A linear rms-flux relation at a confidence level higher than 65 % was recovered for less than 8 % of the cases. We were able to check if the magnitude is log-normally distributed for eight timeseries and found, with a confidence ≥95 %, that this is not the case. [ABSTRACT FROM AUTHOR]

We have investigated a model of an accretion disk around a supermassive black hole in active galactic nuclei (AGN). Three kinds of prescription of viscosity have been examined. It is found that the distinction among the constructed models with these prescriptions is realized when the self-gravity of the disk is dominant over the central gravity in the outer region, though they yield the same consequences for the non-self-gravitating disk. The Toomre instability parameter is less than unity in the outer region, and consequently the disk becomes gravitationally unstable and is broken up into many clumps. It is also found that the appropriate condition for the density and temperature for pumping luminous HO masers is not satisfied in our disk model. The density turns out to be rather high at a distance of the sub-parsec scale from the central black hole. [ABSTRACT FROM AUTHOR]

We undertake a spectral study of a sample of bright X-ray sources taken from six XMM-Newton fields at high galactic latitudes, where AGN are the most populous class. These six fields were chosen such that the observation had an exposure time more than 60 ksec, had data from the EPIC-pn detector in the full-Frame mode and lying at high galactic latitude | b|>25. The analysis started by fitting the spectra of all sources with an absorbed power-law model, and then we fitted all the spectra with an absorbed power-law with a low energy black-body component model.The sources for which we added a black body gave an F-test probability of 0.01 or less (i.e. at 99% confidence level), were recognized as sources that display soft excess. We perform a comparative analysis of soft excess spectral parameters with respect to the underlying power-law one for sources that satisfy this criterion. Those sources, that do not show evidence for a soft excess, based on the F-test probability at a 99% confidence level, were also fitted with the absorbed power-law with a low energy black-body component model with the black-body temperature fixed at 0.1 and 0.2 keV. We establish upper limits on the soft excess flux for those sources at these two temperatures. Finally we have made use of Aladdin interactive sky atlas and matching with NASA/IPAC Extragalactic Database (NED) to identify the X-ray sources in our sample. For those sources which are identified in the NED catalogue, we make a comparative study of the soft excess phenomenon for different types of systems. [ABSTRACT FROM AUTHOR]

Active Galactic Nuclei (AGN), such as Seyfert galaxies, quasars, etc., show light variations in all wavelength bands, with various amplitude and in many time scales. The variations usually look erratic, not periodic nor purely random. Many of these objects also show lognormal flux distribution and RMS-flux relation and power law frequency distribution. So far, the lognormal flux distribution of black hole objects is only observational facts without satisfactory explanation about the physical mechanism producing such distribution in the accretion disk. One of the most promising models based on cellular automaton mechanism has been successful in reproducing PSD (Power Spectral Density) of the observed objects but could not reproduce lognormal flux distribution. Such distribution requires the existence of underlying multiplicative process while the existing SOC models are based on additive processes. A modified SOC model based on cellular automaton mechanism for producing lognormal flux distribution is presented in this paper. The idea is that the energy released in the avalanche and diffusion in the accretion disk is not entirely emitted instantaneously as in the original cellular automaton model. Some part of the energy is kept in the disk and thus increase its energy content so that the next avalanche will be in higher energy condition and will release more energy. The later an avalanche occurs, the more amount of energy is emitted to the observers. This can provide multiplicative effects to the flux and produces lognormal flux distribution. [ABSTRACT FROM AUTHOR]

Accretion onto a supermassive black hole in Active Galactic Nuclei (AGN), Seyfert galaxies and quasars is often accompanied by winds which are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes which are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption ('warm absorbers'). Here we perform 3D calculations of transfer of polarized light in 0.1-10 keV range from hydrodynamical model of warm absorber flow and show that such gas will have a distinct signature when viewed in polarized X-rays and it will be detectable by future dedicated X-ray polarimetry space missions, such as the NASA Gravity and Extreme Magnetism SMEX, GEMS. [ABSTRACT FROM AUTHOR]

We present the review of some new problems in cosmology and physics of stars in connection with future launching of WSO. We discuss three problems. UV observations of distant z>6 quasars allow to obtain information on the soft <1 KeV X-ray radiation of the accretion disk around a supermassive black hole because of its cosmological redshift. Really the region of X-ray radiation is insufficiently investigated because of high galactic absorption. In a result one will get important information on the reionization zone of the Universe. Astronomers from ESO revealed the effect of alignment of electric vectors of polarized QSOs. One of the probable mechanism of such alignment is the conversion of QSO radiation into low mass pseudoscalar particles (axions) in the extragalactic magnetic field. These boson like particles have been predicted by new SUSY particle physics theory. Since the probability of such conversion is increasing namely in UV spectral range one can expect the strong correlation between UV spectral energy distribution of QSO radiation and polarimetric data in the optical range. In the stellar physics one of the interesting problems is the origin of the X-ray sources with super Eddington luminosities. The results of UV observations of these X-ray sources will allow to find the origin of these sources as accreting intermediate mass black holes. [ABSTRACT FROM AUTHOR]

We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with an IDL-based code developed by us. The significance of the observed coincidences was evaluated through Monte Carlo simulations of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found. The percentage of chance coincidences is less than 1%. X-ray hardness ratios of well-known populations of objects were used to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic latitudes (| b|≥10°). At low galactic latitudes (| b|≤10°) most of unidentified X-ray sources (∼94%) lie at | b|≤2°. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties. These tables are intended as a useful tool for researchers interested in particular identifications. [ABSTRACT FROM AUTHOR]

The infrared properties of ULIRGs in samples from the Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey and 6dF Galaxy Survey (SDSS-2dF-6dF Survey) and ULIRGs in the IRAS 1 Jy sample are compared. We find that the infrared properties are quite similar in both the far infrared and the near infrared for those two samples. By using the IRAS two-color diagram and the 2MASS two-color diagram we find that 24 sources in the SDSS-2dF-6dF Survey are candidate Seyfert 1-like sources indicative of strong AGN-dominant nature. [ABSTRACT FROM AUTHOR]

The impact of a cosmic time evolution of the gravitational constant on SN Ia luminosity and AGN/QSO luminosity functions is studied. The gravitational constant scales linearly with the Hubble parameter, its present-day variation being $\dot{G}_{0}/G_{0}\approx 1.9\times 10^{-4}$ Gyr−1, compatible with current bounds from lunar laser ranging. Distance moduli of Type Ia supernovae are fitted with a cosmic expansion factor derived from temperature variations of planetary paleoclimates, and a luminosity dependence on look-back time proportional to the varying gravitational constant is inferred from the Hubble diagram. A fit is performed to the comoving space density of X-ray-selected active galactic nuclei (AGNs) and optically selected quasars (QSOs) extending to redshifts z≈6. The initial steep increase of the AGN space density is reproduced by a redshift evolution depending solely on the Hubble parameter as scaling variable. The AGN luminosity scales with the Hubble parameter, and the scaling exponents of the luminosity function, composed of two competing power laws with exponential cutoff, are obtained. Based on the AGN luminosity function, flux-limited X-ray source counts are investigated. The counting functions are derived and put to test by fitting cumulative number counts of soft X-ray point sources compiled from ROSAT, XMM-Newton, and Chandra surveys. [ABSTRACT FROM AUTHOR]

Locating the exact point of origin of the core radiation in active galactic nuclei (AGN) would represent important progress in our understanding of physical processes in the central engine of these objects. However, due to our inability to resolve the region containing both the central compact object and the jet base, this has so far been difficult. Here, using an analysis in which the lack of resolution does not play a significant role, we demonstrate that it may be impossible even in most radio loud sources for more than a small percentage of the core radiation at radio wavelengths to come from the jet base. We find for 3C279 that ∼85 percent of the core flux at 15 GHz must come from a separate, reasonably stable, region that is not part of the jet base, and that then likely radiates at least quasi-isotropically and is centered on the black hole. The long-term stability of this component also suggests that it may originate in a region that extends over many Schwarzschild radii. [ABSTRACT FROM AUTHOR]

The combination of accretion disks and supersonic jets is used to model many active astrophysical objects, viz., young stars, relativistic stars, and active galactic nuclei. However, existing theories on the physical processes by which these structures transfer angular momentum and energy from disks to jets through viscous or magnetic torques are still relatively approximate. Global stationary solutions do not permit understanding the formation and stability of these structures; and global numerical simulations that include both the disk and jet physics are often limited to relatively short time scales and astrophysically out-of-range values of viscosity and resistivity parameters that are instead crucial to defining the coupling of the inflow/outflow dynamics. Along these lines we discuss self-consistent time-dependent simulations of the launching of supersonic jets by magnetized accretion disks, using high resolution numerical techniques. We shall concentrate on the effects of the disk physical parameters, and discuss under which conditions steady state solutions of the type proposed in the self-similar models of Blandford and Payne can be reached and maintained in a self-consistent nonlinear stationary state. [ABSTRACT FROM AUTHOR]

Nuclear stellar clusters are a common phenomenon in spirals and in starburst galaxies, and they may be a natural consequence of the star formation processes in the central regions of galaxies. HST UV imaging of a few Seyfert 2 galaxies have resolved nuclear starbursts in Seyfert 2 revealing stellar clusters as the main components of the extended emission. However, we do not know whether stellar clusters are always associated with all types of nuclear activity. We present HST NUV and optical images to study the role that stellar clusters play in different types of AGNs. Also with these images, we study the circumnuclear dust morphology as a probe of the circumnuclear environment of AGNs. [ABSTRACT FROM AUTHOR]

I briefly review in this paper the main observational properties of relativistically broadened X-ray spectral lines in Galactic Black Holes and Active Galactic Nuclei, and the (scanty) estimates of their frequency in the corresponding parent populations. The available measurements allow us to derive some constraints on the black hole spin and mass, and on the accretion disk geometry and illumination. [ABSTRACT FROM AUTHOR]

INTEGRAL is operational since more than three years and producing high quality data that allows to detect fainter new hard X-ray sources. The new sources, identified until now, are mostly active galactic nuclei and absorbed or transient high mass X-ray binaries. TeV emission could be expected from the new high mass X-ray binaries accreting dense clumps of stellar wind. INTEGRAL sources with TeV counterparts are discussed. [ABSTRACT FROM AUTHOR]

The ANTARES telescope, currently in construction, is aiming to detect high energy neutrinos. Data from the first line of the detector, which became operational recently, demonstrates that the nominal time and space resolutions are achieved. Various models predict the emission of high energy neutrinos from astrophysical sources such as Supernova Remnants, Microquasars, Active Galactic Nuclei and Gamma Ray Bursts. With the custom designed data acquisition system of this detector, in combination with the existing satellite alert systems, the ANTARES telescope has an increased sensitivity for neutrinos from Gamma Ray Bursts compared to conventional time independent sources. [ABSTRACT FROM AUTHOR]

We investigate the production of gamma-rays in the inverse Compton (IC) scattering process by leptons accelerated inside relativistic blobs in jets of active galactic nuclei. Leptons are injected homogeneously inside the spherical blob and initiate IC e ± pair cascade in the synchrotron radiation (produced by the same population of leptons, SSC model), provided that the optical depth for gamma-rays is larger than unity. It is shown that for likely parameters internal absorption of gamma-rays has to be important. We suggest that new type of blazars might be discovered by the future simultaneous X-ray and γ-ray observations, showing peak emissions in the hard X-rays, and in the GeV γ-rays. Moreover, the considered scenario might be also responsible for the orphan X-ray flares recently reported from BL Lac type active galaxies. [ABSTRACT FROM AUTHOR]

I present the search for V, R, I rapid optical variability of three gamma-ray loud blazars, 3C 454.3, 1ES 1959+650, 1ES 2344+514, performed at the Loiano telescope. The source 3C 454.3 was observed during the decline of the May 2005 outburst. 3C 454.3 and 1ES 2344$+$514 showed rapid variability in one band at least. The data in this work and archival data support the correlation between the occurrence of rapid variability and the flux variation suggested by Howard et~al., AJ 127, 17 (2004). [ABSTRACT FROM AUTHOR]

The extragalactic analogs of the microquasars, the quasars, are strong γ-ray emitters at GeV energies. It is expected that microquasars are also γ-ray sources, because of the analogy with quasars and because theoretical models predict the high-energy emission. There are two microquasars that appear as the possible counterparts for two unidentified high-energy γ-ray sources. [ABSTRACT FROM AUTHOR]

We discuss constraints on black hole spin and spin-related astrophysics as derived from X-ray spectroscopy. After a brief discussion about the robustness with which X-ray spectroscopy can be used to probe strong gravity, we summarize how these techniques can constrain black hole spin. In particular, we highlight XMM-Newton studies of the Seyfert galaxy MCG-6-30-15 and the stellar-mass black hole GX 339-4. The broad X-ray iron line profile, together with reasonable and general astrophysical assumptions, allow a non-rotating black hole to be rejected in both of these sources. If we make the stronger assertion of no emission from within the innermost stable circular orbit, the MCG-6-30-15 data constrain the dimensionless spin parameter to be a > 0.93. Furthermore, these XMM-Newton data are already providing evidence for exotic spin-related astrophysics in the central regions of this object. We conclude with a discussion of the impact that Constellation-X will have on the study of strong gravity and black hole spin. [ABSTRACT FROM AUTHOR]

At luminosities below a few percent of Eddington, accreting black holes switch to a hard spectral state which is very different from the soft blackbody-like spectral state that is found at higher luminosities. The hard state is well-described by a two-temperature, optically thin, geometrically thick, advection-dominated accretion flow (ADAF) in which the ions are extremely hot (up to 1012 K near the black hole), the electrons are also hot (∼109−10.5 K), and thermal Comptonization dominates the X-ray emission. The radiative efficiency of an ADAF decreases rapidly with decreasing mass accretion rate, becoming extremely low when a source reaches quiescence. ADAFs are expected to have strong outflows, which may explain why relativistic jets are often inferred from the radio emission of these sources. It has been suggested that most of the X-ray emission also comes from a jet, but this is less well established. [ABSTRACT FROM AUTHOR]

Significant (marginal) detections of periodic signals have been recently reported in 3 (4) Active Galactic Nuclei. Three of the detections were obtained from long EUVE light curves of moderate-luminosity Seyfert galaxies; the fourth was discovered in Chandra data from the low-luminosity Seyfert 1 galaxy NGC 4395. When compared with Cyg X-1, I find that the period is related to the luminosity as P∝ L 2/3 rather than the expected one-to-one relationship. This result might be explained if the QPO is associated with the inner edge of the optically thick accretion disk, and the inner-edge radius depends on the source luminosity (or black hole mass). A discussion of uncertainties in the period detection methodology is also discussed. [ABSTRACT FROM AUTHOR]

We examine the disc-jet connection in stellar mass and supermassive black holes by investigating the properties of their compact emission in the hard X-ray and radio bands. We compile a sample of ∼100 active galactic nuclei with measured mass, 5 GHz core emission, and 2–10 keV luminosity, together with eight galactic black holes with a total of ∼50 simultaneous observations in the radio and X-ray bands. Using this sample, we study the correlations between the radio ( L R) and the X-ray ( L X) luminosity and the black hole mass ( M). We find that the radio luminosity is correlated with both M and L X, at a highly significant level. We show how this result can be used to extend the standard unification by orientation scheme to encompass unification by mass and accretion rate. [ABSTRACT FROM AUTHOR]

I summarize the main observational properties of low-luminosity AGNs in nearby galaxies to argue that they are the high-mass analogs of black hole X-ray binaries in the “low/hard” state. The principal characteristics of low-state AGNs can be accommodated with a scenario in which the central engine is comprised of three components: an optically thick, geometrically accretion disk with a truncated inner radius, a radiatively inefficient flow, and a compact jet. [ABSTRACT FROM AUTHOR]

The appearance of superluminal radio knots follows drops in the X-ray flux in the FR1 radio galaxy 3C 120 and possibly the FR2 source 3C 111. This corresponds in a very general way to the behavior of the X-ray binary GRS 1915 + 105, but the light curves of the microquasar are much richer in detail. Starting in 2003.7, the character of the radio and X-ray light curves of 3C 120 changed, perhaps signaling a new stage of activity. I discuss here what one might expect when a microquasar is scaled up to AGN dimensions, and compare this with what we see in 3C 120. There is a mismatch between expectations and observations. [ABSTRACT FROM AUTHOR]

In recent years, significant evidence for the similar nature of active galactic nuclei (AGN) and X-ray binaries (XRBs) has been gathered. We describe a unification scheme for accreting black holes following the idea that weakly accreting systems may be jet dominated. This is tested with the radio/X-ray correlation of XRBs and AGN. The established correlation is further used to diagnose ultra-luminous X-ray sources. For higher accretion rates, we explore high-power jets and the effect of Compton cooling of the jet by the accretion disk. [ABSTRACT FROM AUTHOR]

The scale invariance model (Heinz, S. and Sunyaev, R.A.: 2003, MNRAS 343, L59) can be used to derive robust scaling relations between the radio luminosity from accreting black holes and the black hole mass and accretion rate. These relations agree well with the recently found “fundamental plane” of black hole activity (Merloni, A., Heinz, S. and Di Matteo, T.: 2003, MNRAS 345, 1057). This relation provides a new, powerful tool for the comparison of jets from black holes of different masses and accretion rates. The regression coefficients of this relation contain information about the nature of the X-ray emission mechanism driving the correlation. We argue that X-ray synchrotron emission from the base of the jets is unlikely to be the dominant contribution to the X-ray spectrum in most of the sources. [ABSTRACT FROM AUTHOR]

We have recently put forward a ‘unified’ semi-empirical model for the coupling between accretion and jet production in galactic black hole X-ray binaries. In this paper, we summarise this model and briefly discuss relevant considerations that have arisen since its publication. [ABSTRACT FROM AUTHOR]