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 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 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.

scholarly journals The size of the X-ray emitting region in SWIFT J2127.4+5654 via a broad line region cloud X-ray eclipse

2013 ◽  
Vol 436 (2) ◽  
pp. 1588-1594 ◽  
Author(s):  
M. Sanfrutos ◽  
G. Miniutti ◽  
B. Agís-González ◽  
A. C. Fabian ◽  
J. M. Miller ◽  
...  
Keyword(s):  
Broad Line ◽  
X Ray ◽  
Broad Line Region ◽  
Line Region

scholarly journals Broad-line region structure and line profile variations in the changing look AGN HE 1136-2304

2018 ◽  
Vol 619 ◽  
pp. A168 ◽  
Author(s):  
W. Kollatschny ◽  
M. W. Ochmann ◽  
M. Zetzl ◽  
M. Haas ◽  
D. Chelouche ◽  
...  
Keyword(s):  
Seyfert Galaxies ◽  
Spectroscopic Properties ◽  
Emission Lines ◽  
Broad Line ◽  
Spectral Variability ◽  
Continuum Source ◽  
Line Intensities ◽  
Broad Line Region ◽  
Line Region ◽  
Optical Continuum

Aims. A strong X-ray outburst was detected in HE 1136-2304 in 2014. Accompanying optical spectra revealed that the spectral type has changed from a nearly Seyfert 2 type (1.95), classified by spectra taken 10 and 20 years ago, to a Seyfert 1.5 in our most recent observations. We seek to investigate a detailed spectroscopic campaign on the spectroscopic properties and spectral variability behavior of this changing look AGN and compare this to other variable Seyfert galaxies. Methods. We carried out a detailed spectroscopic variability campaign of HE 1136-2304 with the 10 m Southern African Large Telescope (SALT) between 2014 December and 2015 July. Results. The broad-line region (BLR) of HE 1136-2304 is stratified with respect to the distance of the line-emitting regions. The integrated emission line intensities of Hα, Hβ, He I λ5876, and He II λ4686 originate at distances of 15.0−3.8+4.2, 7.5−5.7+4.6, 7.3−4.4+2.8, and 3.0−3.7+5.3 light days with respect to the optical continuum at 4570 Å. The variability amplitudes of the integrated emission lines are a function of distance to the ionizing continuum source as well. We derived a central black hole mass of 3.8 ± 3.1 × 107 M⊙ based on the linewidths and distances of the BLR. The outer line wings of all BLR lines respond much faster to continuum variations indicating a Keplerian disk component for the BLR. The response in the outer wings is about two light days shorter than the response of the adjacent continuum flux with respect to the ionizing continuum flux. The vertical BLR structure in HE 1136-2304 confirms a general trend that the emission lines of narrow line active galactic nuclei (AGNs) originate at larger distances from the midplane in comparison to AGNs showing broader emission lines. Otherwise, the variability behavior of this changing look AGN is similar to that of other AGN.

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