X-ray spectral and eclipsing model of the clumpy obscurer in active galactic nuclei

We present a unification model for a clumpy obscurer in active galactic nuclei (AGN) and investigate the properties of the resulting X-ray spectrum. Our model is constructed to reproduce the column density distribution of the AGN population and cloud eclipse events in terms of their angular sizes and frequency. We developed and released a generalised Monte Carlo X-ray radiative transfer code, XARS, to compute X-ray spectra of obscurer models. The geometry results in strong Compton scattering, causing soft photons to escape also along Compton-thick sight lines. This makes our model spectra very similar to our TORUS previous model. However, only if we introduce an additional Compton-thick reflector near the corona, we achieve good fits to NuSTAR spectra. This additional component in our model can be interpreted as part of the dust-free broad-line region, an inner wall or rim, or a warped disk. It cannot be attributed to a simple disk because the reflector must simultaneously block the line of sight to the corona and reflect its radiation. We release our model as an Xspec table model and present corresponding CLUMPY infrared spectra, paving the way for self-consistent multi-wavelength analyses.

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Soft X-ray Variability and the Covering Fraction of Active Galactic Nuclei

Symposium - International Astronomical Union ◽

10.1017/s0074180900140562 ◽

1989 ◽

Vol 134 ◽

pp. 118-119

Author(s):

Michael A. Strauss ◽

Kenneth W. Wachter ◽

Alexei V. Filippenko

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Line Of Sight ◽

X Rays ◽

Broad Line ◽

X Ray ◽

Broad Line Region ◽

Line Region ◽

Partial Covering

The variability of soft X-rays (0.2 – 2 keV) in some low-luminosity type 1 Seyferts may partly be due to an extrinsic mechanism: dense clouds of gas in the broad-line region, opaque to soft X-rays, move across our line of sight to the X-ray emitting portions of the accretion disk (Reichert, Mushotzky, and Holt 1986; Lawrence and Elvis 1982; Halpern 1984). As the clouds move, the covering fraction changes stochastically. Evidence for partial covering of the X-ray source in low-luminosity AGNs has been seen in soft X-ray spectra by Holt et al. (1980) and Reichert et al. (1985).

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The relationship between X-ray and optical absorbers in active galactic nuclei

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa262 ◽

2020 ◽

Vol 493 (1) ◽

pp. 930-939 ◽

Cited By ~ 3

Author(s):

Gunnar W Jaffarian ◽

C Martin Gaskell

Keyword(s):

Active Galactic Nuclei ◽

Column Density ◽

Scattered Light ◽

Galactic Nuclei ◽

Broad Line ◽

Large Scatter ◽

Standard Type ◽

X Ray

ABSTRACT We present a large compilation of reddening estimates from broad-line Balmer decrements for active galactic nuclei (AGNs) with measured X-ray column densities. The median reddening is E(B − V) ≈ 0.77 ± 0.10 for type-1 to type-1.9 AGNs with reported column densities. This is notably higher than the median reddening of AGNs from the SDSS. We attribute this to the selection bias of the SDSS towards blue AGNs. For other AGNs, we find evidence of a publication bias against reporting low column densities. We find a significant correlation between NH and E(B − V) but with a large scatter of ±1 dex. On average, the X-ray columns are consistent with those predicted from E(B − V) for a solar neighbourhood dust-to-gas ratio. We argue that the large scatter of column densities and reddenings can be explained by X-ray column density variability. For AGNs with detectable broad-line regions (BLRs) that have undergone significant changes of Seyfert type (‘changing-look’ AGNs), we do not find any statistically significant differences in NH or E(B − V) compared to standard type-1 to type-1.9 AGNs. There is no evidence for any type-1 AGNs being Compton thick. We also analyse type-2 AGNs and find no significant correlation between NH and narrow-line region reddening. We find no evidence for a previously claimed anticorrelation. The median column density of LINERs is 22.68 ± 0.75 compared to a column density of 22.90 ± 0.28 for type-2 AGNs. We find the majority of low column density type-2 AGNs are LINERs, but NH is probably underestimated because of scattered light.

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The role of failed accretion disk winds in active galactic nuclei

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320002628 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 82-86 ◽

Cited By ~ 1

Author(s):

Margherita Giustini ◽

Daniel Proga

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Galactic Nuclei ◽

Broad Line ◽

X Ray ◽

Broad Line Region ◽

Line Region ◽

Gravitational Pull ◽

Theoretical Evidence

AbstractBoth observational and theoretical evidence point at outflows originating from accretion disks as fundamental ingredients of active galactic nuclei (AGN). These outflows can have more than one component, for example an unbound supersonic wind and a failed wind (FW). The latter is a prediction of the simulations of radiation-driven disk outflows which show that the former is accompanied by an inner failed component, where the flow struggles to escape from the strong gravitational pull of the supermassive black hole. This FW component could provide a physical framework to interpret various phenomenological components of AGN. Here we briefly discuss a few of them: the broad line region, the X-ray obscurer, and the X-ray corona.

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Are Compton-thin AGNs Globally Compton Thin?

The Astrophysical Journal ◽

10.3847/1538-4357/ac1ff6 ◽

2021 ◽

Vol 922 (1) ◽

pp. 85

Author(s):

P. Tzanavaris ◽

T. Yaqoob ◽

S. LaMassa ◽

A. Ptak ◽

M. Yukita

Keyword(s):

Emission Line ◽

Active Galactic Nuclei ◽

Column Density ◽

Line Emission ◽

Galactic Nuclei ◽

Line Of Sight ◽

X Ray ◽

Hydrogen Column Density ◽

Model Configuration

Abstract We select eight nearby active galactic nuclei (AGNs) which, based on previous work, appear to be Compton-thin in the line of sight. We model with mytorus their broadband X-ray spectra from 20 individual observations with Suzaku, accounting self-consistently for Fe Kα line emission, as well as direct and scattered continuum from matter with finite column density and solar Fe abundance. Our model configuration allows us to measure the global, out of the line of sight, equivalent hydrogen column density separately from that in the line of sight. For 5 out of 20 observations (in 3 AGNs) we find that the global column density is in fact ≳1.5 × 1024 cm−2, consistent with the distant scattering matter being Compton-thick. For a fourth AGN, two out of five observations are also consistent with being Compton-thick, although with large errors. Some of these AGNs have been reported to host relativistically broadened Fe Kα emission. Based on our modeling, the Fe Kα emission line is not resolved in all but two Suzaku observations, and the data can be fitted well with models that only include a narrow Fe Kα emission line.

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Supernova Fragments and the Origin of the Rapid X-ray Variability

Symposium - International Astronomical Union ◽

10.1017/s0074180900175643 ◽

1994 ◽

Vol 159 ◽

pp. 371-371

Author(s):

R. Cid Fernandes ◽

R. Terlevich ◽

G. Tenorio-Tagle ◽

J. Franco ◽

M. Rozyczka

Keyword(s):

Active Galactic Nuclei ◽

Luminosity Function ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Broad Line ◽

X Ray ◽

Broad Line Region ◽

Line Region

The Starburst model for Radio Quiet Active Galactic Nuclei proved able to explain the origin of the broad line region, the variability characteristics of line and continuum in Seyfert galaxies, X-ray spectra, the luminosity function of QSOs and etc. But can we understand the rapid X-ray variability observed in several AGN with supernovae?

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Pumping of H2O Megamasers

Highlights of Astronomy ◽

10.1017/s1539299600019298 ◽

1998 ◽

Vol 11 (2) ◽

pp. 960-963

Author(s):

Moshe Elitzur

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Broad Line ◽

X Ray ◽

Star Forming ◽

Broad Line Region ◽

Star Forming Regions ◽

Disk Rotation ◽

Line Region ◽

Pump Mechanism

AbstractStrong H2O maser emission is detected from active galactic nuclei (AGN) as well as Galactic objects such as star-forming regions and late-type stars. In spite of the widely different luminosities of the different masers, a common pump mechanism seems adequate: neutral collisions at densities of ˜ 108-1010 cm-3 and temperatures of ˜ 250-500 K. The different properties of the various masers can be attributed to geometry. Although disk rotation controls the AGN maser geometry it does not directly determine the dimensions. X-ray radiation and spiral shocks have been suggested as the heating sources of H2O megamasers. Both are capable of explaining the observations, and the radiative scenario seems best understood in terms of chance alignment of standard broad-line-region clouds. It is not yet clear whether these different proposals produce distinct maser signatures.

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X-ray occultations in active galactic nuclei: distribution in size of orbiting clouds and total mass content in the cloud ensemble

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935632 ◽

2019 ◽

Vol 628 ◽

pp. A26

Author(s):

P. Pietrini ◽

G. Torricelli-Ciamponi ◽

G. Risaliti

Keyword(s):

Active Galactic Nuclei ◽

Total Mass ◽

Galactic Nuclei ◽

Broad Line ◽

Number Density ◽

Mass Content ◽

X Ray ◽

Cloud Properties ◽

Line Region ◽

Short Time

In recent years the short-time X-ray variability of AGNs has been interpreted in terms of varying absorption from the temporary occultation of the primary X-ray source itself owing to the passage of absorbing clouds. Detailed analyses have shown that these clouds are located in the same region and have physical properties similar to those of broad line region (BLR) emitting clouds. The aim of this paper is to investigate in detail whether the same group of orbiting clouds can account for BLR emitting cloud properties and X-ray eclipsing cloud properties as well. To this purpose we looked for a distribution in size for the cloud number density capable of fulfilling the observational requirements of the two groups. The existence of such a distribution not only proves that BLR clouds and eclipsing clouds can be part of the same “family”, but also allows us to estimate the total mass content in clouds orbiting around an AGN black hole.

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Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽

10.3390/galaxies9020042 ◽

2021 ◽

Vol 9 (2) ◽

pp. 42

Author(s):

Claudia M. Raiteri ◽

Massimo Villata

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Plasma Jets ◽

Line Of Sight ◽

Optical Behaviour ◽

Relativistic Jets ◽

Comprehensive Picture ◽

Multi Wavelength ◽

Extreme Variability ◽

Continuous Range

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

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Steps toward Determination of the Size and Structure of the Broad‐Line Region in Active Galactic Nuclei. X. Variability of Fairall 9 from Optical Data

The Astrophysical Journal Supplement Series ◽

10.1086/313046 ◽

1997 ◽

Vol 112 (2) ◽

pp. 271-283 ◽

Cited By ~ 41

Author(s):

M. Santos‐Lleo ◽

E. Chatzichristou ◽

C. Mendes de Oliveira ◽

C. Winge ◽

D. Alloin ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Optical Data ◽

Broad Line ◽

Broad Line Region ◽

Line Region ◽

Size And Structure

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Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources

The Astrophysical Journal ◽

10.3847/1538-4357/ac1fee ◽

2021 ◽

Vol 922 (2) ◽

pp. 159

Author(s):

A. Traina ◽

S. Marchesi ◽

C. Vignali ◽

N. Torres-Albà ◽

M. Ajello ◽

...

Keyword(s):

Spectral Analysis ◽

Energy Range ◽

Active Galactic Nuclei ◽

Column Density ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Line Of Sight ◽

Broad Energy Range ◽

Larger Sample ◽

Broad Energy

Abstract We present the joint Chandra, XMM-Newton, and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of 10 low-redshift (z ≤ 0.05), candidates Compton-thick (CT) Active Galactic Nuclei selected in the 15–150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N H,S ) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N H,z = [0.58–0.62] × 1024 cm−2, but the N H,S , beyond the CT threshold (N H,S = [1.41–1.78] × 1024 cm−2), suggests a “patchy” scenario for the distribution of the circumnuclear matter. ESO 565-G019 has both CT l.o.s. and N H,S column densities (N H,z > 2.31 × 1024 cm−2 and N H,S > 2.57 × 1024 cm−2, respectively). The use of physically motivated models, coupled with the broad energy range covered by the data (0.6–70 keV and 0.6–40 keV, for NGC 3081 and ESO 565-G019, respectively) allows us to constrain the covering factor of the obscuring material, which is C TOR = [0.63–0.82] for NGC 3081, and C TOR = [0.39–0.65] for ESO 565-G019.

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