Search

The bulk of X‐ray spectroscopic studies of active galactic nuclei (AGN) are focused on local (z<0.1$$ z<0.1 $$) sources with low‐to‐moderate (<0.3) Eddington ratio (λEdd$$ {\lambda}_{\mathrm{Edd}} $$). It is then mandatory to overcome this limitation and improve our understanding of highly accreting AGN. In this work, we present the preliminary results from the analysis of a sample of ∼70$$ \sim 70 $$ high‐λEdd$$ {\lambda}_{\mathrm{Edd}} $$ radio‐quiet AGN at 0.06≤z≤3.3$$ 0.06\le z\le 3.3 $$, based on the 10th release of the XMM‐Newton serendipitous source catalog, that we named as XMM‐Newton High‐Eddington Serendipitous AGN Sample (X‐HESS). Almost ∼35%$$ \sim 35\% $$ of the X‐HESS AGN have multi‐epoch archival observations and ∼70%$$ \sim 70\% $$ of the sources can rely on simultaneous OM optical data. First results reveal sources showing signatures of ultra‐fast outflows and remarkable long‐ and short‐term X‐ray flux variations. Indeed in SDSS J095847.88+690532.7 (z∼1.3$$ z\sim 1.3 $$), one of the most densely monitored objects hosting a ∼109 M⊙$$ \sim 1{0}^9\;{M}_{\odot } $$ supermassive black hole, we discovered a variation of the soft X‐ray flux by a factor of >2 over approximately one week (rest‐frame). Large variations in the power‐law continuum photon index Γ$$ \Gamma $$ are also observed, questioning expectations from previously reported Γ−λEdd$$ \Gamma -{\lambda}_{\mathrm{Edd}} $$ relations, for which Γ≥2$$ \Gamma \ge 2 $$ would be a ubiquitous hallmark of AGN with λEdd∼1$$ {\lambda}_{\mathrm{Edd}}\sim 1 $$. [ABSTRACT FROM AUTHOR]

We present the results regarding the analysis of an intensive monitoring of the Active Galactic Nucleus (AGN) NGC 7469. We observed the source for 4 months with almost daily cadence in the ugriz bands, using the IO:O on the Liverpool Telescope. We measured the lags with respect to the u band and found a clear change in the lag spectrum between the first and the second half of the campaign. Given that the source varies on different timescales during these two segments, it is likely that different components are dominating the variability at different times. This result further confirms that reverberation models require a more complex geometry than a static illuminating point source and that particular attention has to be given in the interpretation of these delays. [ABSTRACT FROM AUTHOR]

Our work aims to identify the miscellaneous radio galaxies (MRGs) using the LOFAR Two‐meter Sky Survey First Data Release (LoTSS DR1) at 144 MHz. The miscellaneous radio sources are very rare because of their peculiar morphological radio structure, which does not match with the known classes of radio sources. We find only four such MRGs by manually examining 18,500 samples. The peculiar morphology is not found in other radio frequencies 1400, 150, and 325 MHz. We estimate different physical parameters like spectral index, radio luminosity, and radio power of these sources. Among the four MRGs, J1428+4556 has the highest linear size of 3.972 Mpc and can be considered a giant radio galaxy. We also try to present the known galaxy cluster association with these MRGs. We find that the MRGs are associated with at least one galaxy cluster within 1 Mpc radius. The basic parameters such as mass, radius, and richness of the clusters are also noted. [ABSTRACT FROM AUTHOR]

We estimated the radiative efficiency and spin value for a number of local active galactic nuclei (AGNs) with z<0.34 using three popular models connecting the radiative efficiency with such parameters of AGNs as mass of supermassive black hole (SMBH), angle between the line of sight and the axis of the accretion disk and bolometric luminosity. Analysis of the obtained data shows that the spin value decreases with cosmic time, which is in agreement with results of theoretical calculations for low‐redshift AGNs of other authors. Also, we found that the spin value increases with the increasing mass of SMBH and bolometric luminosity. This is the expected result that corresponds to theoretical calculations. Analysis of the distribution of the spin values shows a pronounced peak in the distribution in 0.750.75 and ∼50% of objects have spin a>0.5. These results are in good agreement with our previous results and with the results of other authors. [ABSTRACT FROM AUTHOR]

We study a sample of 67 active galactic nuclei (AGN) with moderate to strong Feii emission to investigate the relation between the observed AGN continuum and the lines produced by the broad line region (BLR), in particular, Feii. We found that the continuum in the optical/near‐infrared can be described in terms of two components: a power‐law, characterized by the spectral index α, and hot dust emission, represented by a Plank function of temperature T. These two parameters seem not to be related to the strength of Feii emission. In addition to Feii, we study other low‐ionization BLR lines such as Oi and Caii (hereafter CaT). We found that the full‐width at half maximum of these three lines are similar, suggesting that they are produced in the same spatial region of the BLR. We measure the Feii strength in the optical and the near‐infrared region and found that they are strongly correlated. This result evidences the presence of a common excitation mechanism for the Feii emission in the wavelength interval 4000–24000 Å. [ABSTRACT FROM AUTHOR]

The collection of papers in this special issue represents the selected papers presented at the 13th Serbian Conference on Spectral Line Shapes in Astrophysics held in Belgrade in a blended format (online and in‐person) from August 23 to August 27, 2021. Here we shortly describe the conference and some ideas given during the conference and published in this special issue of Astronomische Nachrichten. [ABSTRACT FROM AUTHOR]

We investigate the broad line profiles emitted from a system supermassive binary black hole (SMBBH) having elliptical orbits and a low mass ratio of m2/m1∼0.1. Our model assumes a super Eddington accretion flow in the case of a smaller component, whereas the massive component has very small or negligible accretion, therefore supposing that no broad‐line region (BLR) is attached to it. Thus, the proposed SMBBH system contains one moving BLR, associated with the less massive component and one circum‐binary BLR. We study the effect of the different total mass of the system (ranging from 106 to 108 Solar masses) on the Hβ line profiles and to the continuum and line light curves. The resulted broad line profiles are asymmetric and shifted, and are varying during the orbital period. The asymmetry in the broad line profiles is discussed in terms of expected differences between the proposed model of the SMBBH with one active component and the scenario of a recoiling black hole. We discuss the periodicity detected in the line and continuum light curves, as well as in the variations of the line asymmetry and shift. [ABSTRACT FROM AUTHOR]

We report preliminary results on the analysis of the continuum and Hβ light curves of the type‐1 active galactic nucleus (AGN) NGC 5548. We notice a clear signature of shallowing in the trend between the Hβ and the continuum luminosities. We attempt the recovery of this observed Hβ emission trend as a response to large continuum flux increase using CLOUDY photoionization simulations. We explore a wide range in the physical parameters space for modeling the Hβ emission from the broad‐line region (BLR) appropriate for this source. We employ a constant density, single‐cloud model approach in this study and successfully recover the observed shallowing of the Hβ emission with respect to rising AGN continuum. With our modeling, we are able to provide the constraints on the local BLR cloud density and recover the BLR distances (from the continuum source) consistent with the Hβ reverberation mapping estimates. We further discuss the implications of the BLR covering factor and their sizes on recovering the observed trend. [ABSTRACT FROM AUTHOR]

The last few years have seen the confirmation of several trends associated with the quasar main sequence. The idea of a main sequence for quasars is relatively recent, and its full potential for the observational classification and contextualization of quasars' properties has yet to be fully exploited. The main sequence drivers are discussed in terms of the properties of extreme objects. We briefly summarize developments that constrain the viewing angle of the accretion disk in a particular class of quasars (extreme Population B, radiating at low Eddington ratio), as well as inferences on the chemical composition of the broad line emitting gas, and on the nature of radio emission along the quasar main sequence. [ABSTRACT FROM AUTHOR]

Most bulge‐dominated galaxies host black holes (BHs) with masses that tightly correlate with the masses of their bulges. This may indicate that the BHs may regulate galaxy growth, or vice versa, or that they may grow in lock‐step. The quest to understand how, when, and where those BHs formed motivates much of extragalactic astronomy. Here we focus on a population of galaxies with active BHs in their nuclei (active galactic nuclei [AGN]), that are fully or partially hidden by dust and gas: The emission from the broad line region is either completely or partially obscured with a visual extinction of one or above. This limit, though not yet precise, appears to be the point at which the populations of AGN may evolve differently. We highlight the importance of finding and studying those dusty AGN at redshifts between one and three, the epoch when the universe may have gone through its most dramatic changes. We emphasize the need for future large multiplexed spectroscopic instruments that can perform dedicated surveys in the optical and near‐infrared to pin down the demographics of such objects, and study their reddening properties, star‐formation histories, and excitation conditions. These key studies will shed light on the role of BHs in galaxy evolution during the epoch of peak growth activity. [ABSTRACT FROM AUTHOR]

The IceCube project transformed a cubic kilometer of transparent natural Antarctic ice into a Cherenkov detector. It discovered PeV‐energy neutrinos originating beyond our galaxy with an energy flux that is comparable to that of GeV‐energy gamma rays and EeV‐energy cosmic rays. These neutrinos provide the only unobstructed view of the cosmic accelerators that power the highest energy radiation reaching us from the universe. The results from IceCube's first decade of operations, foremost the measurement of the diffuse neutrino flux from the universe using multiple techniques is reviewed. The multimessenger data that identified the supermassive black hole TXS 0506+056 as a source of cosmic neutrinos is subsequently reviewed and attention is drawn to accumulating indications that cosmic neutrinos are associated with gamma‐ray‐obscured active galaxies, that is, the energy in gamma rays that accompanies cosmic neutrinos emerges at MeV energies, or below. Reaching beyond 10 PeV energy, cosmic neutrinos provide a natural beam to study neutrinos themselves. [ABSTRACT FROM AUTHOR]

Active galactic nucleus (AGN) feedback at z∼1−3 is believed to take place in the presence of thick columns of gas and dust, leading to heavily obscured systems that are challenging to detect at optical and X‐ray wavelengths but are transparent at radio and mid‐IR (MIR) wavelengths. MIR color diagnostics using the widefield infrared space explorer (WISE) observations can identify the most luminous and heavily obscured AGNs, which are believed to represent a transient phase of rapid massive black hole growth. By combining both mid‐IR and radio diagnostics, we have identified a sample of 155 ultraluminous and obscured quasars (0.47 mJy) radio emission in the NRAO VLA Sky Survey (NVSS) and Faint Images of the Radio Sky at Twenty‐one centimeters (FIRST). High‐resolution very large array (VLA) imaging has revealed compact source morphologies on angular scales <0.2″ (1.7 kpc at z∼2) for the majority of our sources. Broadband radio spectra of the entire sample, constructed from our 10 GHz VLA observations and archival radio data show that 63% of the sample has peaked or curved spectral shapes consistent with those typically seen in young radio AGN (e.g., gigahertz peaked spectrum [GPS] and compact steep spectrum [CSS] sources). Overall, our sample is consistent with a population of recently triggered, young radio jets caught in a unique evolutionary stage in which they reside in a dense interstellar medium (ISM). [ABSTRACT FROM AUTHOR]

Although radio observations have been historically seen as less valuable than optical observations, today's broadband radio spectra of peaked spectrum sources reveal detailed physics from within the inner region of the galaxy, on spatial scales beyond what an optical telescope can resolve. Peaked radio spectra are thought to be evolving into large‐scale radio galaxies, although an over‐abundance of the most compact sources reveals that a significant fraction are confined within their host galaxies. Furthermore, at the lowest luminosities, these sources are largely unknown, and may reveal the small‐scale precursors of FR‐I galaxies. Here, I summarize the previous work exploring the properties of low‐luminosity peaked radio sources, and the future work that extends on this within even deeper radio observations of well‐studied fields. [ABSTRACT FROM AUTHOR]

We report the detection of outflowing molecular gas in the center of the nearby (z = 0.014) massive radio galaxy NGC 6328. The radio core of the galaxy, PKS B1718‐649, is identified as a gigahertz peaked spectrum source with a compact (2 pc) double radio lobe morphology. We used ALMA CO(2–1) and CO(3–2) observations at 100 pc resolution to study the gas kinematics up to ∼5kpc from the galaxy center. While the bulk of the molecular gas is settled in a highly warped disk, in the inner 300 pc of the disk and along with the orientation of the radio jet, we identified high‐excitation and high‐velocity gas that cannot be attributed to any regular kinematic component based on our detailed 3D modeling of the ALMA data. The high‐velocity dispersion in the gas also suggests that it is not part of an inflowing, shredding structure. These results suggest the presence of a molecular outflow of 3–8 solar masses per year. The outflow possibly originated from the interaction of the jet with the dense interstellar medium, even though the radio emission is detected closer to the center than the outflow. In this sense, this source resembles NGC 1377, 4C31.04, and ESO 420‐G13, in which the outflows are linked to faint or past jet activity. [ABSTRACT FROM AUTHOR]

The evolutionary stage of a powerful radio source originated by an active galactic nucleus is related to its linear size. Following the evolution models, intrinsically compact objects would evolve into the population of classical radio galaxies. However, the fraction of young radio sources in flux density‐limited samples is much larger than what is expected from the number counts of large radio sources, suggesting the existence of short‐lived objects. We present results of multi‐epoch very large array and very long baseline array observations of a sub‐sample of extreme GPS sources that should be at the very beginning of their radio evolution. We also briefly introduce a new project aiming at determining the incidence of short‐lived objects among a statistically complete sample of young radio sources. [ABSTRACT FROM AUTHOR]

In this article, we summarize our recent progress in observational studies of jet collimation in active galactic nuclei. We focus on the investigation of a relation between the properties of the collimation zone and the AGN accretion mode, recently proposed by Boccardi, B., Perucho, M., Casadio, C. et al., 2021, A&A, 647, A67. We also discuss the efforts made by our team to increase the still limited number of sources that can be imaged on sufficiently small spatial scales to probe such zone, and we present first results for new candidates. [ABSTRACT FROM AUTHOR]

We aim to leverage the transformational science enabled by the Event Horizon Telescope (EHT) to study the physics of, and near, the black holes in a sample of galaxies covering a large parameter space in supermassive black hole mass, accretion rate, and jet power. To this end, we work on a sample of nearby galaxies whose directly measured black hole masses and distances imply that 40 micro‐arcsec EHT observations will resolve the central engine at <100 Schwarzschild radius resolution. To complement the near‐future EHT observations, we attempt to constrain the accretion properties of nearby active galactic nuclei by modeling the broadband spectral energy distribution using a general relativistic Monte Carlo radiative transfer code. These results will provide apriori information that is vital for an accurate ray‐tracing of EHT millimeter maps of accretion flows in the future. [ABSTRACT FROM AUTHOR]

Energetic feedback driven by the large‐scale (100's of kpc) lobes of classical radio galaxies is known to play an important role in shaping galaxy evolution. However, the prevalence of young and compact jets – and their impact on the interstellar medium – remains an open question. Multi‐epoch radio surveys with cadences of years to decades offer a promising means of identifying even faint (mJy‐level) jets that are compact and potentially young on the basis of variability. Recently, a comparison of images from the Very Large Array Sky Survey (VLASS) and the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey has revealed a population of distant (0.2

We report the radio continuum properties for several samples of peaked spectrum (PS) radio sources. Broadband spectra of the objects were analyzed using the RATAN‐600 six‐frequency (1.2–22 GHz) observations and available literature data, obtained on a time scale of 20–30 years. We discuss statistical differences in radio properties for several AGN types with peaked spectra and focus on PS quasars at high redshifts (z>3). We confirm that a relatively small fraction (1–2%) of bright PS sources can be considered genuine gigahertz‐peaked spectrums (GPSs) when they have been monitored densely and for a long time. The contamination of GPS source samples by blazars is getting stronger as the redshift increases, and we confirm that it is underestimated due to lack of systematic multifrequency observations. [ABSTRACT FROM AUTHOR]

CSS/GPS objects represent a key stage in the evolution of powerful radio AGN in which the jets are expanding through the denser, kpc‐scale ISM in the host galaxies. Therefore, it is important both to understand how such radio AGN are triggered as galaxies evolve and to directly quantify the impact of the outflows induced by the jet‐cloud interactions. Here, we show that CSS/GPS sources are likely to be triggered in galaxy mergers, just like powerful radio AGN in general. However, they are both more gas‐rich and have higher star formation rates on average than their more extended counterparts. Also, whereas observations frequently show evidence for strong jet‐cloud interactions in CSS/GPS in the form of warm outflows, in most cases these warm outflows are unlikely to be energetic enough to affect the star formation histories of the entire host galaxies outside the central kpc. Rather, much of the mass, energy, and momentum of the outflows appear to be tied up in neutral and molecular outflows, which may have a more important impact on the host galaxies. Finally, we consider whether CSS/GPS sources are impostors in flux‐limited samples due to the effect of the strong jet‐cloud interactions on their radio luminosities. [ABSTRACT FROM AUTHOR]

Compact symmetric objects (CSOs), young jetted‐active galactic nuclei of overall projected size <1 kpc, are of great interest due to their youth and evolution. The classification was introduced to distinguish between ∼95% of powerful compact extragalactic radio sources in flux density limited samples that are dominated by asymmetric emission due to relativistic beaming from jets aligned close to the line of sight and ∼5% of objects that are not. The original classification criteria were (a) overall projected diameter smaller than 1 kpc, (b) identified center of activity, and (c) symmetric jet structure about the center. There is confusion and erosion of the value of the CSO classification due to misclassifications. Many jets contain compact bright features outside the core, resulting in a gigahertz peaked spectrum total spectrum and a "compact double" appearance, and some objects with jet axes aligned close to the line of sight appear symmetric because the approaching jet is projected on both sides of the core. To eliminate the confusion, we propose adding (d) slow radio variability and (e) low apparent velocity of bright features moving along the jets to the above CSO criteria. We are compiling a catalog of CSOs using these five criteria to eliminate the confusion of Doppler boosting. [ABSTRACT FROM AUTHOR]

In this contribution, we present the first numerical simulations of a relativistic outflow propagating through the inner hundreds of parsecs of its host galaxy, including atomic and ionized hydrogen, and the cooling effects of ionization. Our results are preliminary, but we observe efficient shock ionization of atomic hydrogen in interstellar clouds. The mean density of the interstellar medium in these initial simulations is lower than that expected in typical galaxies, which makes cooling times longer and thus no recombination is observed inside the shocked region. The velocities achieved by the shocked gas in the simulations are in agreement with observational results, although with a wide spectrum of values. [ABSTRACT FROM AUTHOR]

We present the results of our study of the relationship between Fanaroff‐Riley type 0 (FR0) radio galaxies and gigahertz‐peaked spectrum (GPS) sources. Quasi‐simultaneous radio spectra of 34 FR0s were obtained at 2.25–22.3 GHz with the radio telescope RATAN‐600 in 2020–2021 during 2–6 epochs. Most FR0s have flat radio spectra, but we found many spectra with a peaked shape. Due to this fact and the compact nature of FR0s, we suggest their possible relationship with compact steep‐spectrum (CSS)/GPS radio sources. We analyzed broadband radio spectra of the 34 FR0s using the RATAN‐600 measurements and available literature data. There are 14 FR0 objects which can be CSS/GPS radio source candidates. Most FR0s have broader radio spectra than those of genuine GPS sources, with FWHM>2 like in blazars. Most spectral indices at the frequencies below and above the peak do not correspond to the values typical of canonical GPS sources. We classified 3 FR0s as low‐power GPS sources according to the canonical criteria. The key issue is the variability properties of FR0s. Some FR0s demonstrate a variability level of up to 25% on a time scale of 1 year according to the RATAN‐600 measurements. The flare phenomena in FR0 objects can imply a relationship between them and blazars. [ABSTRACT FROM AUTHOR]

The peaked spectrum (PS) radio sources are sub‐kpc in size and have a peak in the radio spectrum. The compact steep specrum (CSS) sources range from about 1 kpc to an adopted upper limit on projected linear size of 20 kpc. Because of their galactic‐scale range of size, the PS and CSS radio sources interact strongly with the ISM of this host galaxy. This means that the PS and CSS sources can be a significant source of the AGN feedback. The PS and CSS sources are a key phase in radio source evolution. Yet, there is substantial uncertainty regarding the origin of these sources, their lifetimes, and their evolution. There are many interesting open questions regarding the PS and CSS radio sources. Here, in this short introduction to the topic, I focus on the origin stories for these sources and how progress might be made. [ABSTRACT FROM AUTHOR]

According to radiative models, radio galaxies are predicted to produce γ‐rays from the earliest stages of their evolution onwards. The study of the high‐energy emission from young radio sources is crucial for providing information on the most energetic processes associated with these sources, the actual region responsible for this emission, as well as the structure of the newly born radio jets. Despite systematic searches for young radio sources at γ‐ray energies, only a handful of detections have been reported so far. Taking advantage of more than 11 years of Fermi‐large area telescope (LAT) data, we investigate the γ‐ray emission of 162 young radio sources (103 galaxies and 59 quasars), the largest sample of young radio sources used so far for a γ‐ray study. We analyzed the Fermi‐LAT data of each source separately to search for a significant detection. In addition, we performed the first stacking analysis of this class of sources in order to investigate the γ‐ray emission of the young radio sources that are undetected at high energies. In this note, we present the results of our study and we discuss their implications for the predictions of γ‐ray emission from this class of sources. [ABSTRACT FROM AUTHOR]

Cluster‐central gigahertz peak and compact steep‐spectrum (CSS) sources offer an opportunity to study the earliest phases of active galactic nucleus (AGN) feedback, but few have yet been examined in detail. We present results from radio and X‐ray observations of 1321+045, a CSS source in a 4.4 keV cluster at z=0.263. The cluster has a strongly cooling core, and disturbances from a minor cluster merger may have triggered a period of jet activity which formed the 16 kpc radio lobes 2.0−0.2+0.3Myr ago. However, new very long baseline array (VLBA) imaging shows a ∼20 pc jet on a different projected axis, which is probably only a few hundred years old. We consider possible histories for the system, with either one or two periods of jet activity. While this single system is informative, a broader study of the youngest cluster‐central radio sources is desirable. [ABSTRACT FROM AUTHOR]

We present the spectral analysis with the Nuclear Spectroscopic Telescope Array (NuSTAR) of four isolated galaxies with active galactic nuclei selected from the 2MIG catalogue: NGC 5347, ESO 438‐009, MCG‐02‐09‐040, and IGR J11366‐6002. We also used the Swift/Burst Alert Telescope (BAT) data up to ∼150 keV for MCG 02‐09‐040, ESO 438‐009, and IGR J11366‐6002 as well as the Swift/XRT data in 0.3–10 keV energy band for NGC 5347, ESO 438‐009, and IGR J11366‐6002. All the sources appear to have the reflected spectrum component with different reflection fractions in addition to the primary power‐law continuum. We found that power‐law indices for these sources lie between 1.6 and 1.8. The spectra of two sources, NGC 5347 and MCG‐02‐09‐040, show the Fe Kα emission line. For both of these sources, the Fe Kα lines have a significant value of EW ∼1 keV. The X‐ray spectrum of NGC 5347 is best fitted by a pure reflection model with Ecut ∼ 117 keV and without the presence of any additional primary power‐law component. We also found that the X‐ray spectrum of MCG‐02‐09‐040 shows the presence of heavy neutral obscuration of NH ∼ 1024 cm−2. However, this provides a non‐physical value of reflection in the case with fitting by a simple reflection model. A more appropriate fit is obtained with adopting the physical Monte Carlo‐based model as BNTorus. It allowed us to determine the absorption value of NH ∼ 1.04 × 1024 cm−2 and reasonable power‐law index of Γ ≈ 1.63. Results for MCG‐02‐09‐040 are presented for the first time. [ABSTRACT FROM AUTHOR]

We present the spectral analysis with the Nuclear Spectroscopic Telescope Array (NuSTAR) of four isolated galaxies with active galactic nuclei selected from the 2MIG catalogue: NGC 5347, ESO 438‐009, MCG‐02‐09‐040, and IGR J11366‐6002. We also used the Swift/Burst Alert Telescope (BAT) data up to ∼150 keV for MCG 02‐09‐040, ESO 438‐009, and IGR J11366‐6002 as well as the Swift/XRT data in 0.3–10 keV energy band for NGC 5347, ESO 438‐009, and IGR J11366‐6002. All the sources appear to have the reflected spectrum component with different reflection fractions in addition to the primary power‐law continuum. We found that power‐law indices for these sources lie between 1.6 and 1.8. The spectra of two sources, NGC 5347 and MCG‐02‐09‐040, show the Fe Kα emission line. For both of these sources, the Fe Kα lines have a significant value of EW ∼1 keV. The X‐ray spectrum of NGC 5347 is best fitted by a pure reflection model with Ecut ∼ 117 keV and without the presence of any additional primary power‐law component. We also found that the X‐ray spectrum of MCG‐02‐09‐040 shows the presence of heavy neutral obscuration of NH ∼ 1024 cm−2. However, this provides a non‐physical value of reflection in the case with fitting by a simple reflection model. A more appropriate fit is obtained with adopting the physical Monte Carlo‐based model as BNTorus. It allowed us to determine the absorption value of NH ∼ 1.04 × 1024 cm−2 and reasonable power‐law index of Γ ≈ 1.63. Results for MCG‐02‐09‐040 are presented for the first time. [ABSTRACT FROM AUTHOR]

Blazars represent the dominant population of the extragalactic γ‐ray sources in the universe. These sources exhibit some characteristic properties such as strong and nonthermal continuum emission over the entire electromagnetic spectrum, from radio to Tera electron Volts (TeV) γ‐rays, with rapid variability on all timescales. The emission at radio and optical wavelengths is highly polarized with significant variation. The fastest variability in the blazar emission is observed during the flaring activity, which is an important observational property of blazars. In this paper, we describe various methods to characterize the temporal variability in the multiwavelength light curves of blazars. We also provide a detailed description of the set of statistical parameters that are used to quantify the level of variability present in the time series. Implications of the information derived from the variability study to probe the physics of blazars using multiwavelength observations are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we investigate radio properties of active galaxies taken from the reference [Véron‐Cetty & Véron (2010)] catalog. The galaxies are limited to magnitudes in the range of 12m − 19m. We have cross‐correlated the list with radio catalogs and selected those galaxies that have data on six or more radio fluxes at different wavelengths. As a result, we have 198 galaxies that satisfy these conditions. Using SDSS DR15, we have obtained 96 spectroscopic identifications of the 198 objects. After the classification, 85% of the 96 objects have changed their types. Available data on the classification of these objects and our classification showed that 56.7% of them are Seyfert galaxies. For all the objects, we have built radio spectra and estimated radio spectral indices. As a result, we obtain α‾=−0.6089±0.056(α‾Seyfert=−0.6013±0.027, α‾LINER=−0.5955±0.025, α‾HII=−0.6672±0.039, α‾Comp.=−0.7128±0.043). We discuss the radio properties of active galaxies based on their radio spectral indices. [ABSTRACT FROM AUTHOR]

By applying different statistically robust methods, we analyze the time lag between the continuum and ionized line‐emission (Mg II line) light curves for the distant bright quasar CTS C30.10 (redshift z∼0.9). The data were obtained by the 10‐meter South African Large Telescope (SALT) telescope in South Africa. In detail, we demonstrate the application of several methods using the interpolated cross‐correlation function (ICCF), discrete correlation function (DCF), z‐transformed discrete correlation function (zDCF), von Neumann estimator, and the JAVELIN code package. In particular, we discuss the uncertainties of these methods. In conclusion, we find that the quasar lies on the broad‐line region (BLR) size—monochromatic luminosity power‐law scaling, RBLR∝L51001/2, which was already confirmed for low‐redshift sources. In case, the BLR size–luminosity relation holds for other distant sources, quasars could be used to probe cosmological models as "standard candles" complementary to supernovae Ia. [ABSTRACT FROM AUTHOR]

XMM-Newton is capable of making a transformational advance in our understanding of how luminous accreting black holes work, by dedicating about 10% of future observing time to long observations, of order megaseconds, to X-ray variable active galactic nuclei (AGN) research. This would enable reverberation studies, already a commonplace feature of AGN, to proceed to the next level and follow the behavior of the powerful dynamic corona. Such a dedicated legacy program can only be carried out with XMM-Newton. [ABSTRACT FROM AUTHOR]

It is generally believed that the high energy end of synchrotron emission, generated by the most energetic tail of relativistic electrons in the jets, account for the X-ray emission of high-energy peaked BL Lac objects (HBLs) and the optical emission of intermediate-energy peaked BL Lac objects (IBLs). It is thus expected that both should show similar variability characteristics. One of the important variability parameters is the inter-band time lag which probes the acceleration and cooling of relativistic particles responsible for the emission. The switches between soft and hard lags have been detected in the intra-day X-ray variability of a few HBLs, which is not the case for the intra-day optical variability of IBLs yet. We present the results of our intra-night optical observations for BL Lacertae, aiming at searching for hard lags of its optical variations, performed with the 80 cm telescope in fourteen nights of 2010 September-November. Intra-night changes of ∼0.2 mag were detected in most of nights. The intra-night variability amplitude tends to become larger from red to blue wavelength, and the optical spectrum hardens with increasing brightness. The intra-night variations correlate between different wavebands, but we did not find significant time lags, either soft or hard. Nevertheless, on November 2, the B band variations showed a sign of lagging the R band ones by 317±214 s. The claim of this hard lag is strongly limited by the photometric precision and time resolution. Therefore, the switches between soft and hard lags of IBLs in the optical bands needs further demonstration with more higher quality observations. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We discuss the origin of the low-energy cutoff, or LEC, seen in the radio spectra of many extragalactic jets and relate this to the spin of the supermassive black holes that presumably power them. Pion decay via proton-proton collisions is a possible mechanism to supply a secondary positron population with a low energy limit. We expect that pion production would occur in advection dominated accretion flows or ADAFs. In radiatively inefficient ADAFs the heat energy of the accreting gas is unable to radiate in less than the accretion time and the particle temperature could be high enough so that thermal protons can yield such pion production. Strong starbursts are another option for the injection of a truncated particle population into the jet. The role of both mechanisms is discussed with respect to the black hole spin estimate. The energy demanded to produce the pion decay process involves a minimum threshold for kinetic energy of the interacting protons. Therefore the mean proton speed in the flow can determine whether a LEC is generated. In ADAFs the random velocity of the protons can exceed the minimum speed limit of pion production around the jet launching region in the innermost part of the flow. Finally we summarize the additional work needed to put the model assumptions on a more rigorous basis. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]