scholarly journals X-RAY VARIABILITY STUDY OF POLAR SCATTERED SEYFERT1 GALAXIES

2014 ◽  
Vol 54 (4) ◽  
pp. 266-270
Author(s):  
Tobias Beuchert ◽  
Jörn Wilms ◽  
Matthias Kadler ◽  
Anna Lia Longinotti ◽  
Matteo Guainazzi ◽  
...  
Keyword(s):  
Column Density ◽  
Polar Region ◽  
Line Of Sight ◽  
Viewing Angle ◽  
Spectral Variability ◽  
X Ray ◽  
Central Engine ◽  
Pass Through ◽  
High Level ◽  
Variability Study

We study 12 Seyfert 1 galaxies with a high level of optical polarization. Optical light emerging from the innermost regions is predominantly scattered in a polar region above the central engine directly in our line of sight. These sources show characteristics of Seyfert 2 galaxies, e.g. polarized broad lines. The polarization signatures suggest a viewing angle of 45°, classifying them as intermediate Seyfert 1/2 types. The unified model predicts this line of sight to pass through the outer layer of the torus resulting in significant soft X-ray variability due to a strongly varying column density. The aim is to find evidence for this geometrical assumption in the spectral variability of all available historical observations of these sources by <em>XMM-Newton</em> and <em>Swift</em>.

scholarly journals Probing the circumnuclear absorbing medium of the buried AGN in NGC 1068 through NuSTAR observations

2020 ◽  
Vol 492 (3) ◽  
pp. 3872-3884 ◽  
Author(s):  
A Zaino ◽  
S Bianchi ◽  
A Marinucci ◽  
G Matt ◽  
F E Bauer ◽  
...  
Keyword(s):  
Time Scales ◽  
Line Of Sight ◽  
Nuclear Region ◽  
Spectral Variability ◽  
Absorbing Medium ◽  
X Ray ◽  
Innermost Part ◽  
Monitoring Campaign ◽  
Ngc 1068 ◽  
Thick Material

ABSTRACT We present the results of the latest NuSTAR monitoring campaign of the Compton-thick Seyfert 2 galaxy NGC 1068, composed of four ∼50 ks observations performed between 2017 July and 2018 February to search for flux and spectral variability on time-scales from 1 to 6 months. We detect one unveiling and one eclipsing event with time-scales less than 27 and 91 d, respectively, ascribed to Compton-thick material with NH = (1.8 ± 0.8) × 1024 and ≥ (2.4 ± 0.5) × 1024 cm−2 moving across our line of sight. This gas is likely located in the innermost part of the torus or even further inward, thus providing further evidence of the clumpy structure of the circumnuclear matter in this source. Taking advantage of simultaneous Swift–XRT observations, we also detected a new flaring ULX, at a distance d ∼ 30 arcsec (i.e. ∼2 kpc) from the nuclear region of NGC 1068, with a peak X-ray intrinsic luminosity of (3.0 ± 0.4) × 1040 erg s−1 in the 2–10 keV band.

Tracing Small-Scale Fluctuations in the Soft X-ray Background

1997 ◽  
Vol 166 ◽  
pp. 321-324
Author(s):  
R. Warwick ◽  
I. Hutchinson ◽  
R. Willingale ◽  
K. Kuntz ◽  
S. Snowden
Keyword(s):  
Column Density ◽  
Galactic Halo ◽  
Inverse Correlation ◽  
Line Of Sight ◽  
Small Scale ◽  
X Ray ◽  
Hydrogen Column Density ◽  
X Ray Background ◽  
Counting Statistics ◽  
Made In

AbstractAn overlapping set of ROSAT PSPC observations made in a region of very low Galactic foreground column density, has been used to investigate variations in the soft X-ray background on angular scales of 15′ – 5°. In the ¼ keV band there is a clear inverse correlation of the count-rate with the line-of-sight hydrogen column density. However, after correcting for this absorption effect, strong residual fluctuations remain in the data, with an amplitude which is significantly larger than that due to the counting statistics or the confusion of unresolved discrete sources. In contrast a similar analysis for the ¾ and 1.5 keV ROSAT bands shows no evidence for an excess signal. The most likely origin of the ¼ keV fluctuations would seem to be in a patchy distribution of ~ 106 K gas in the Galactic halo.

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.

X-Ray Characteristics of Water Megamaser Galaxies

2017 ◽  
Vol 13 (S336) ◽  
pp. 141-142
Author(s):  
K. Leiter ◽  
M. Kadler ◽  
J. Wilms ◽  
J. Braatz ◽  
C. Grossberger ◽  
...  
Keyword(s):  
Column Density ◽  
Control Sample ◽  
Line Of Sight ◽  
Homogeneous Sample ◽  
X Ray ◽  
Maser Sources ◽  
Water Maser

AbstractWe have compiled the X-ray characteristic properties for a unique and homogeneous sample of Type 2 AGN with water megamaser activity observed by XMM-Newton and for a control sample of non-maser galaxies, both analyzed in a uniform way. A comparison of the luminosity distributions confirms previous results (from smaller and/or less systematic studies) that water maser galaxies appear more luminous than non-maser sources. In addition, the maser phenomenon is associated with more complex X-ray spectra, higher column densities and higher equivalent widths of the Fe Kα line. Both a sufficiently luminous X-ray source and a high absorbing column density in the line of sight favor the appearance of the water megamaser phenomenon in AGN.

scholarly journals Probing the nuclear and circumnuclear properties of NGC 6300 using X-ray observations

2020 ◽  
Vol 499 (4) ◽  
pp. 5396-5409
Author(s):  
Arghajit Jana ◽  
Arka Chatterjee ◽  
Neeraj Kumari ◽  
Prantik Nandi ◽  
Sachindra Naik ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Column Density ◽  
Line Emission ◽  
Physical Models ◽  
Line Of Sight ◽  
Physical Parameters ◽  
Energy Bands ◽  
Telescope Array ◽  
Iron Line ◽  
X Ray

ABSTRACT We present the results obtained from a detailed X-ray timing and spectral analysis of the Seyfert 2 galaxy NGC 6300 by using observations from the Suzaku observatory, theChandra X-ray Observatory and the Nuclear Spectroscopic Telescope Array(NuSTAR) mission between 2007 and 2016. We calculate the variance and the rms fractional variability of the source in different energy bands and we find variabilities in various energy bands. Spectral properties of the source are studied by using various phenomenological and physical models. The properties of the Compton clouds, reflection, Fe Kα line emission and soft X-ray excess are studied in detail. Several physical parameters of the source are extracted and investigated to establish the presence/absence of any correlation between them. We also investigate the nature of the circumnuclear ‘torus’ and we find that the torus is not uniform, but clumpy. The observed changes in the line-of-sight column density can be explained in terms of transiting clouds. The iron line-emitting region is found to be different in the different epochs of observations. We also observe that the torus and the nucleus independently evolve over the years.

scholarly journals Recent Satellite Observations of X-ray Emission from AGN

2000 ◽  
Vol 195 ◽  
pp. 77-87
Author(s):  
H. Kunieda
Keyword(s):  
Accretion Disks ◽  
Broad Band ◽  
Satellite Observations ◽  
Spectral Variability ◽  
Edge Structure ◽  
Iron Line ◽  
X Ray ◽  
Central Engine ◽  
Photoionized Plasmas ◽  
Strong Radiation

Recent X-ray satellite observations provide plenty of spectral information with high resolution in a broad band. Major results from the spectral observations are related to the interaction of the power-law continuum flux with the ambient plasmas and accretion disks. The most prominent result is the broad iron-line feature from Seyfert I galaxies which is interpreted as the emission from the relativistic accretion disk. Doppler shift and boosting, as well as gravitational redshifts, are considerable at the distance of several Schwarzschild radii from the central black hole. Strong radiation from the central engine ionizes the ambient material of AGN. Edge structure found at around 0.8 keV is attributed to highly ionized oxygen of O VII and O VIII. Some iron emission lines from Seyfert II galaxies are emitted by highly photoionized plasmas. The study of fast temporal and spectral variability is the key approach to examine the emission mechanism and structure of the central vicinity of AGN. In 2000, two X-ray observatories (Chandra and XMM will be in orbit, and they will provide us with deeper insights of the physics around the black holes and of the physics of hot plasmas.

scholarly journals Are Compton-thin AGNs Globally Compton Thin?

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.

The X-ray spectrum and variability of active galaxies

1979 ◽  
Vol 366 (1726) ◽  
pp. 435-448 ◽  
Keyword(s):  
Proportional Counter ◽  
Column Density ◽  
Active Galaxies ◽  
Line Of Sight ◽  
X Ray ◽  
Ngc 4151 ◽  
Hydrogen Column Density ◽  
System Experiment

Spectra have been obtained with the use of the M. S. S. L. proportional counter system, experiment C on board Ariel 5, for 13 X-ray sources for which identifications as active galaxies seem to be reasonably sound. The data for 12 of these sources are presented here. Spectra have been obtained at different epochs for the sources NGC 5128 and NGC 4151. These data indicate that for both of these sources not only intensity variability has been observed, but also changes in the line of sight hydrogen column density.

scholarly journals X-ray spectral model from clumpy torus and its application to Circinus galaxy

2019 ◽  
Vol 15 (S341) ◽  
pp. 314-315
Author(s):  
Atsushi Tanimoto
Keyword(s):  
Monte Carlo Simulation ◽  
Active Galactic Nucleus ◽  
Column Density ◽  
Radial Direction ◽  
Spectral Model ◽  
Angular Width ◽  
Line Of Sight ◽  
Power Law Distribution ◽  
X Ray ◽  
Hydrogen Column Density

AbstractWe construct an X-ray spectral model for the clumpy torus in an active galactic nucleus (AGN), utilizing the Monte Carlo simulation for Astrophysics and Cosmology framework (MONACO: Odaka et al.2016). The geometry of the torus is the same as that in Nenkova et al. (2008), which assumes a power law distribution of clumps in the radial direction and a normal distribution in the elevation direction. We apply our model to the broadband X-ray spectrum of the Circinus galaxy observed with XMM-Newton, Suzaku, and NuSTAR. Our model can well reproduce the observed X-ray spectrum, yielding a hydrogen column density along the line-of-sight ${N_{\rm{H}}^{\rm{LOS}}} = 4.86_{ - 0.04}^{ + 0.07} \times {10^{24}}$ cm−2 and a torus angular width ${sigma = 14.7_{ - 0.39}^{ + 0.44}}$ degree.

scholarly journals X-ray analysis of SDSS J165202.60+172852.4, an obscured quasar with outflows at peak galaxy formation epoch

2021 ◽  
Vol 502 (3) ◽  
pp. 3769-3779
Author(s):  
Yuzo Ishikawa ◽  
Andy D Goulding ◽  
Nadia L Zakamska ◽  
Fred Hamann ◽  
Andrey Vayner ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Column Density ◽  
High Redshift ◽  
Accretion Disc ◽  
Emission Lines ◽  
Line Of Sight ◽  
X Ray ◽  
Spatially Resolved ◽  
Depth View ◽  
Selection Of

ABSTRACT We report on deep XMM–Newton and NuSTAR observations of the high redshift, z = 2.94, extremely red quasar (ERQ), SDSS J165202.60+172852.4, with known galactic ionized outflows detected via spatially resolved [O iii] emission lines. X-ray observations allow us to directly probe the accretion disc luminosity and the geometry and scale of the circumnuclear obscuration. We fit the spectra from the XMM–Newton/EPIC and NuSTAR detectors with a physically motivated torus model and constrain the source to exhibit a near Compton-thick column density of NH = (1.02$^{+0.76}_{-0.41}$) × 1024 cm−2, a near edge-on geometry with the line-of-sight inclination angle of θi = 85°, and a scattering fraction of fsc ∼ 3  per cent. The absorption-corrected, intrinsic 2–10 keV X-ray luminosity of L2–10= (1.4$^{+1}_{-1}$) × 1045 erg s−1 reveals a powerful quasar that is not intrinsically X-ray weak, consistent with observed trends in other ERQs. We also estimate the physical properties of the obscuration, although highly uncertain: the warm ionized scattering density of ne ∼ 7.5 × (102–103) cm−3 and the obscuration mass of $M_{\rm obsc} \sim 1.7\times (10^4\!-\!10^6)\,{\rm M}_{\odot}$. As previously suggested with shallower X-ray observations, optical and infrared selection of ERQ has proved effective in finding obscured quasars with powerful outflow signatures. Our observations provide an in-depth view into the X-ray properties of ERQs and support the conclusions of severely photon-limited studies of obscured quasar populations at high redshifts.

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