scholarly journals Incoherent fast variability of X-ray obscurers

2020 ◽  
Vol 634 ◽  
pp. A65 ◽  
Author(s):  
B. De Marco ◽  
T. P. Adhikari ◽  
G. Ponti ◽  
S. Bianchi ◽  
G. A. Kriss ◽  
...  
Keyword(s):  
Column Density ◽  
Timing Analysis ◽  
Seyfert Galaxies ◽  
Fast Response ◽  
Broad Line ◽  
X Ray ◽  
Line Region ◽  
Timing Properties ◽  
The Impact ◽  
High Column

Context. Obscuration events caused by outflowing clumps or streams of high column density and low ionised gas, shown to absorb the X-ray continuum heavily, have been witnessed across a number of Seyfert galaxies. Aims. We report on the X-ray spectral-timing analysis of the December 2016 obscuration event in NGC 3783, which was aimed at probing variability of the X-ray obscurer on the shortest possible timescales. The main goals of this study are to obtain independent constraints on the density and, ultimately on the distance of the obscuring gas, as well as to characterise the impact of variable obscuration on the observed X-ray spectral-timing characteristics of Seyfert galaxies. Methods. We carried out a comparative analysis of NGC 3783 during unobscured (using archival 2000–2001 XMM-Newton data) and obscured states (using XMM-Newton and NuSTAR data from the 2016 observational campaign). The analysed timescales range between ten hours and about one hour. This study was then generalised to discuss the signatures of variable obscuration in the X-ray spectral-timing characteristics of Seyfert galaxies as a function of the physical properties of the obscuring gas. Results. The X-ray obscurer in NGC 3783 is found to vary on timescales between about one hour to ten hours. This variability is incoherent with respect to the variations of the X-ray continuum. A fast response (on timescales shorter than about 1.5 ks) of the ionisation state of the obscuring gas to the short timescale variability of the primary X-ray continuum provides a satisfactory interpretation of all the observed X-ray spectral-timing properties. This study enabled us to put independent constraints on the density and location of the obscuring gas. We found the gas to have a density of ne >  7.1 × 107 cm−3, which is consistent with a location in the broad line region.

scholarly journals Ubiquitous Column Density Variability in Seyfert 2 Galaxies

2002 ◽  
Vol 19 (1) ◽  
pp. 155-157 ◽  
Author(s):  
G. Risaliti ◽  
M. Elvis ◽  
F. Nicastro
Keyword(s):  
Column Density ◽  
Seyfert Galaxies ◽  
Broad Line ◽  
X Ray ◽  
Preliminary Results ◽  
Broad Line Region ◽  
Line Region ◽  
Standard Scenario ◽  
Region Scale ◽  
Almost All

AbstractWe present a study of X-ray column density variability in Seyfert 2 galaxies. We show that variations in NH are observed in almost all the objects with multiple hard X-ray observations. Variation timescales (as short as a few months in several cases) are not in agreement with the standard scenario of a parsec-scale toroidal absorber. We propose that the X-ray absorber in Seyfert galaxies is located much nearer to the centre than previously assumed, on the broad line region scale. An extension of the model by M. Elvis (2000) can explain the observed variability. We also show preliminary results of NH variability search inside single X-ray observations, which suggest that variations can occur on timescales of a few 104 s.

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

2019 ◽  
Vol 629 ◽  
pp. A16 ◽  
Author(s):  
Johannes Buchner ◽  
Murray Brightman ◽  
Kirpal Nandra ◽  
Robert Nikutta ◽  
Franz E. Bauer
Keyword(s):  
Active Galactic Nuclei ◽  
Column Density ◽  
Galactic Nuclei ◽  
Line Of Sight ◽  
Broad Line ◽  
X Ray ◽  
Line Region ◽  
Self Consistent ◽  
Multi Wavelength ◽  
Table Model

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.

scholarly journals X-ray analysis of the accreting supermassive black hole in the radio galaxy PKS 2251+11

2019 ◽  
Vol 625 ◽  
pp. A26
Author(s):  
S. Ronchini ◽  
F. Tombesi ◽  
F. Vagnetti ◽  
F. Panessa ◽  
G. Bruni
Keyword(s):  
Black Hole ◽  
Power Law ◽  
Radio Galaxy ◽  
Timing Analysis ◽  
Seyfert Galaxies ◽  
Radio Galaxies ◽  
Broad Line ◽  
X Ray ◽  
Supermassive Black Hole ◽  
Link Type

Context. We have investigated the dichotomy between jetted and non-jetted active galactic nuclei (AGNs), focusing on the fundamental differences of these two classes in the accretion physics onto the central supermassive black hole (SMBH). We tested the validity of the unification model of AGNs through the characterization of the mutual interaction between accreting and outflowing matter in radio galaxies. Aims. Our aim is to study and constrain the structure, kinematics and physical state of the nuclear environment in the broad line radio galaxy (BLRG) PKS 2251+11. The high X-ray luminosity and the relative proximity make such AGN an ideal candidate for a detailed analysis of the accretion regions in radio galaxies. The investigation will help to shed light on the analogies and differences between the BLRGs and the larger class of radio-quiet Seyfert galaxies and hence on the processes that trigger the launch of a relativistic jet. Methods. We performed a spectral and timing analysis of a ∼64 ks observation of PKS 2251+11 in the X-ray band with XMM-Newton. We modeled the spectrum considering an absorbed power law superimposed to a reflection component. We performed a time-resolved spectral analysis to search for variability of the X-ray flux and of the individual spectral components. Results. We find that the power law has a photon index Γ = 1.8 ± 0.1, absorbed by an ionized partial covering medium with a column density NH = (10.1 ± 0.8) × 1023 cm−2, a ionization parameter log ξ = 1.3 ± 0.1 erg s−1 cm and a covering factor f ≃ 90%. Considering a density of the absorber typical of the broad line region (BLR), its distance from the central SMBH is of the order of r ∼ 0.1 pc. An Fe Kα emission line is found at 6.4 keV, whose intensity shows variability on timescales of hours. We derive that the reflecting material is located at a distance r ≳ 600rs, where rs is the Schwarzschild radius. Conclusions. Concerning the X-ray properties, we found that PKS 2251+11 does not differ significantly from the non-jetted AGNs, confirming the validity of the unified model in describing the inner regions around the central SMBH, but the lack of information regarding the state of the very innermost disk and SMBH spin still leaves unconstrained the origin of the jet.

scholarly journals A Possible Mechanism to Explain the Narrow Line Variability of Seyfert Galaxies on Timescales of Months

1987 ◽  
Vol 121 ◽  
pp. 223-226
Author(s):  
Nikolay G. Bochkarev
Keyword(s):  
Phase Transfer ◽  
Seyfert Galaxies ◽  
Broad Line ◽  
Line Flux ◽  
Gas Emission ◽  
X Ray ◽  
Line Intensities ◽  
Broad Line Region ◽  
Line Region ◽  
Narrow Emission

Gas in the shadow of clouds in the outer parts of the broad line region can radiate a considerable fraction (dozens of percent) of the narrow emission line flux. The variability of the X-ray luminosity of the central source should result in significant variations of the gas emission on a timescale of months. Particularly strong changes of line intensities and column densities of gas in the shadow (~ 1023 cm−2) can be produced by phase transfer between two thermally stable fluids with temperatures 10–20×103 K and 40–100×103 K, which can exist in the shadow of clouds.

X-ray observations of IRAS selected Seyfert galaxies and obscuration of the broad-line region

1988 ◽  
Vol 324 ◽  
pp. 767 ◽  
Author(s):  
M. J. Ward ◽  
C. Done ◽  
A. C. Fabian ◽  
A. F. Tennant ◽  
R. A. Shafer
Keyword(s):  
Seyfert Galaxies ◽  
Broad Line ◽  
X Ray ◽  
Broad Line Region ◽  
Line Region

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

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?

scholarly journals X-Ray Structure between the Innermost Disk and Optical Broad-line Region in NGC 4151

2018 ◽  
Vol 865 (2) ◽  
pp. 97 ◽  
Author(s):  
J. M. Miller ◽  
E. Cackett ◽  
A. Zoghbi ◽  
D. Barret ◽  
E. Behar ◽  
...  
Keyword(s):  
Broad Line ◽  
X Ray ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
Line Region

scholarly journals Spectral Variability in Seyfert Galaxies

1987 ◽  
Vol 121 ◽  
pp. 161-167
Author(s):  
B.M. Peterson
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Broad Line ◽  
Spectral Variability ◽  
Broad Line Region ◽  
Broad Emission ◽  
Line Region ◽  
Order Of Magnitude ◽  
Optical Continuum

Recent observations of spectral variability in active galactic nuclei have established the connection between the broad emission-line and optical continuum flux changes. The inferred size of the broad-line region is at least an order of magnitude smaller than conventional estimates based on photoionization models, which leads to new conclusions about the nature of the broad-line region.

Sign in / Sign up

Export Citation Format

Share Document