Statistical significance of the relationship between X-ray luminosity and variability timescale in active galactic nuclei

Nature ◽  
1987 ◽  
Vol 328 (6133) ◽  
pp. 784-785 ◽  
Author(s):  
J. B. Stephen ◽  
L. Bassani ◽  
E. Caroli ◽  
G. Di Cocco
Keyword(s):  
Active Galactic Nuclei ◽  
Statistical Significance ◽  
Galactic Nuclei ◽  
X Ray ◽  
The Relationship

On the relationship between optically selected and X-ray-selected active galactic nuclei

1986 ◽  
Vol 301 ◽  
pp. 124 ◽  
Author(s):  
A. Franceschini ◽  
I. M. Gioia ◽  
T. Maccacaro
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
The Relationship

scholarly journals The Relationship of Hard X‐Ray and Optical Line Emission in Low‐Redshift Active Galactic Nuclei

2005 ◽  
Vol 634 (1) ◽  
pp. 161-168 ◽  
Author(s):  
T. M. Heckman ◽  
A. Ptak ◽  
A. Hornschemeier ◽  
G. Kauffmann
Keyword(s):  
Active Galactic Nuclei ◽  
Line Emission ◽  
Galactic Nuclei ◽  
X Ray ◽  
Optical Line ◽  
Relationship Of ◽  
The Relationship

scholarly journals High density of active galactic nuclei in the outskirts of distant galaxy clusters

2019 ◽  
Vol 623 ◽  
pp. L10 ◽  
Author(s):  
E. Koulouridis ◽  
I. Bartalucci
Keyword(s):  
Active Galactic Nuclei ◽  
Galaxy Clusters ◽  
Statistical Significance ◽  
Galactic Nuclei ◽  
Average Density ◽  
Point Sources ◽  
Source Surface ◽  
Essential Property ◽  
X Ray ◽  
Massive Clusters

We present a study of the distribution of X-ray detected active galactic nuclei (AGN) in the five most massive, M500SZ > 1014 M⊙, and distant, z ∼ 1, galaxy clusters in the Planck and South Pole Telescope (SPT) surveys. The spatial and thermodynamic individual properties of each cluster have been defined with unprecedented accuracy at this redshift using deep X-ray observations. This is an essential property of our sample in order to precisely determine the R500Yx radius of the clusters. For our purposes, we computed the X-ray point-like source surface density in 0.5 R500Yx wide annuli up to a clustercentric distance of 4 R500Yx, statistically subtracting the background and accounting for the respective average density of optical galaxies. We found a significant excess of X-ray point sources between 2 and 2.5 R500Yx at the 99.9% confidence level. The results clearly display for the first time strong observational evidence of AGN triggering in the outskirts of high-redshift massive clusters with such a high statistical significance. We argue that the particular conditions at this distance from the cluster centre increase the galaxy merging rate, which is probably the dominant mechanism of AGN triggering in the outskirts of massive clusters.

scholarly journals On the relationship between black hole mass and X-ray variability amplitude in the low-mass regime of active galactic nuclei

2014 ◽  
Vol 10 (S312) ◽  
pp. 73-74
Author(s):  
H. Pan ◽  
W. Yuan ◽  
X.-L. Zhou ◽  
X. Dong ◽  
B. Liu
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Power Spectrum Density ◽  
Black Hole Mass ◽  
X Ray ◽  
Spectrum Density ◽  
Simple Extrapolation ◽  
Low Mass ◽  
The Relationship

AbstractRecent studies of active galactic nuclei (AGN) found a statistical inverse scaling between the X-ray normalized excess variance σrms2 (variability amplitude) and the black hole mass spanning over MBH = 106 − 109M⊙. We present a study of this relation by including AGN with MBH = 105 − 106M⊙. It is found that the relation is no longer a simple extrapolation of the known inverse proportion, but starts to flatten around 106M⊙. This behavior can be understood by the shape of the power spectrum density of AGN and its dependence on the black hole mass.

scholarly journals The relationship between X-ray variability amplitude and black hole mass in active galactic nuclei

2005 ◽  
Vol 358 (4) ◽  
pp. 1405-1416 ◽  
Author(s):  
Paul M. O'Neill ◽  
Kirpal Nandra ◽  
Iossif E. Papadakis ◽  
T. J. Turner
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Black Hole Mass ◽  
X Ray ◽  
The Relationship

scholarly journals Correlation between relativistic reflection fraction and photon index in NuSTAR sample of Seyfert 1 AGN

2020 ◽  
Vol 495 (3) ◽  
pp. 3373-3386
Author(s):  
Savithri H Ezhikode ◽  
Gulab C Dewangan ◽  
Ranjeev Misra ◽  
Ninan Sajeeth Philip
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Accretion Disc ◽  
Telescope Array ◽  
X Ray ◽  
Photon Index ◽  
The Relationship ◽  
Reflection Component

ABSTRACT The primary X-ray emission from active galactic nuclei (AGNs), described by a power-law, irradiates the accretion disc producing reflection features in the spectrum. The reflection features arising from the inner regions of the disc can be significantly modified by the relativistic effects near the black hole. We investigate the relationship between the relativistic reflection fraction Rf, defined as the ratio of the coronal intensity that illuminates the accretion disc to the coronal intensity observed directly, and the hard X-ray photon index Γ of a Nuclear Spectroscopic Telescope Array (NuSTAR) sample of Seyfert 1 galaxies. The X-ray spectra are modelled using relxill code that helps to directly obtain the reflection fraction of a relativistically smeared reflection component. The parameter Rf depends on the amount of Comptonized X-ray emission intercepted by the inner accretion disc. We found a positive correlation between Γ and Rf in our sample. Seed photons from a larger area of an accretion disc entering the corona will result in increased cooling of the coronal plasma, giving rise to steeper X-ray spectrum. The corona irradiating the larger area of the disc will result in higher reflection fraction. Thus, the observed Rf –Γ relation is most likely related to the variations in the disc–corona geometry of AGNs.

Polarization Variability of Active Galactic Nuclei and X‐Ray Binaries

1997 ◽  
Vol 487 (1) ◽  
pp. 142-152 ◽  
Author(s):  
Gang Bao ◽  
Petr Hadrava ◽  
Paul J. Wiita ◽  
Ying Xiong
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
X Ray Binaries

scholarly journals Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 36
Author(s):  
Yoshiyuki Inoue ◽  
Dmitry Khangulyan ◽  
Akihiro Doi
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Thermal Activity ◽  
X Ray ◽  
Cascade Models ◽  
Coronal Activity ◽  
Ngc 1068 ◽  
High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

scholarly journals Hot gaseous atmospheres of rotating galaxies observed with XMM–Newton

2020 ◽  
Vol 499 (4) ◽  
pp. 5163-5174
Author(s):  
A Juráňová ◽  
N Werner ◽  
P E J Nulsen ◽  
M Gaspari ◽  
K Lakhchaura ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Active Galactic Nuclei ◽  
Spiral Galaxy ◽  
Galactic Nuclei ◽  
X Ray ◽  
Hot Gas ◽  
Heating And Cooling ◽  
Theoretical Predictions ◽  
Central Regions ◽  
Gaseous Atmospheres

ABSTRACT X-ray emitting atmospheres of non-rotating early-type galaxies and their connection to central active galactic nuclei have been thoroughly studied over the years. However, in systems with significant angular momentum, processes of heating and cooling are likely to proceed differently. We present an analysis of the hot atmospheres of six lenticulars and a spiral galaxy to study the effects of angular momentum on the hot gas properties. We find an alignment between the hot gas and the stellar distribution, with the ellipticity of the X-ray emission generally lower than that of the optical stellar emission, consistent with theoretical predictions for rotationally supported hot atmospheres. The entropy profiles of NGC 4382 and the massive spiral galaxy NGC 1961 are significantly shallower than the entropy distribution in other galaxies, suggesting the presence of strong heating (via outflows or compressional) in the central regions of these systems. Finally, we investigate the thermal (in)stability of the hot atmospheres via criteria such as the TI- and C-ratio, and discuss the possibility that the discs of cold gas present in these objects have condensed out of the hot atmospheres.

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