scholarly journals Ensemble quasar spectral variability from the XMM-Newton Serendipitous Source Catalogue

2016 ◽  
Vol 12 (S324) ◽  
pp. 249-250
Author(s):  
Roberto Serafinelli ◽  
Fausto Vagnetti ◽  
Riccardo Middei
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Spectral Slope ◽  
High Luminosity ◽  
Spectral Variability ◽  
General Behaviour ◽  
Large Sample ◽  
X Ray ◽  
Spectral Models ◽  
Reflection Component

AbstractVariations of the X-ray spectral slope have been found in many Active Galactic Nuclei (AGN) at moderate luminosities and redshifts, typically showing a “softer when brighter” behaviour. However, similar studies are not usually performed for high-luminosity AGNs. We present an analysis of the spectral variability based on a large sample of quasars in wide intervals of luminosity and redshift, measured at several different epochs, extracted from the fifth release of the XMM Newton Serendipitous Source Catalogue. Our analysis confirms a “softer when brighter” trend also for our sample, extending to high luminosity and redshift the general behaviour previously found. These results can be understood in light of current spectral models, such as intrinsic variations of the X-ray primary radiation, or superposition with a constant reflection component.

scholarly journals Cosmological Evolution of the Central Engine in High-Luminosity, High-Accretion Rate AGN

2014 ◽  
Vol 1 (1) ◽  
pp. 90-95
Author(s):  
Matteo Guainazzi
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Rate ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Cosmological Evolution ◽  
High Luminosity ◽  
X Ray ◽  
Central Engine ◽  
The Status ◽  
Multi Wavelength

In this paper I discuss the status of observational studies aiming at probing the cosmological evolution of the central engine in high-luminosity, high-accretion rate Active Galactic Nuclei (AGN). X-ray spectroscopic surveys, supported by extensive multi-wavelength coverage, indicate a remarkable invariance of the accretion disk plus corona system, and of their coupling up to redshifts z≈6. Furthermore, hard X-ray (<em>E</em> &gt;10 keV) surveys show that nearby Seyfert Galaxies share the same central engine notwithstanding their optical classication. These results suggest that the high-luminosity, high accretion rate quasar phase of AGN evolution is homogeneous over cosmological times.

scholarly journals The coronal temperature of NGC 4388 and NGC 2110 measured with INTEGRAL

2019 ◽  
Vol 629 ◽  
pp. A54 ◽  
Author(s):  
F. Ursini ◽  
L. Bassani ◽  
A. Malizia ◽  
A. Bazzano ◽  
A. J. Bird ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Spherical Geometry ◽  
High Energy ◽  
Coronal Temperature ◽  
Signal To Noise ◽  
X Ray ◽  
Good Signal ◽  
High Energy Emission ◽  
Reflection Component

Aims. We aim to measure the physical properties of the hot X-ray corona of two active galactic nuclei, NGC 4388 and NGC 2110. Methods. We analysed the hard X-ray (20–300 keV) INTEGRAL spectrum in conjunction with archival XMM–Newton and NuSTAR data. Results. The X-ray spectrum of both sources is phenomenologically well described by an absorbed cut-off power law. In agreement with previous results, we find no evidence of a Compton reflection component in these sources. We obtain a high-energy cut-off of 200−40+75 keV for NGC 4388 and 320−60+100 keV for NGC 2110. A fit with a thermal Comptonisation model yields a coronal temperature of 80−20+40 keV and 75−15+20 keV, respectively, and an optical depth of approximately two, assuming a spherical geometry. The coronal temperature and luminosity of both sources are consistent with pair production that acts as a thermostat for the thermal plasma. These results emphasise the importance of good signal-to-noise X-ray data above 100 keV to probe the high-energy emission of AGNs.

scholarly journals The spatial extension of extended narrow line regions in MaNGA AGN

2019 ◽  
Vol 489 (1) ◽  
pp. 855-867 ◽  
Author(s):  
Jianhang Chen ◽  
Yong Shi ◽  
Ross Dempsey ◽  
David R Law ◽  
Yanmei Chen ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Large Distance ◽  
Linear Relation ◽  
Galactic Nuclei ◽  
Narrow Line ◽  
High Luminosity ◽  
Large Sample ◽  
Spatially Resolved ◽  
Nearby Galaxies ◽  
Log Linear

ABSTRACT In this work, we revisit the size–luminosity relation of the extended narrow line regions (ENLRs) using a large sample of nearby active galactic nuclei (AGNs) from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The ENLRs ionized by the AGN are identified through the spatially resolved BPT diagram, which results in a sample of 152 AGN. By combining our AGN with the literature high-luminosity quasars, we found a tight log-linear relation between the size of the ENLR and the AGN $\rm [O\, III]$λ5007 Å luminosity over four orders of magnitude of the $\rm [O\, III]$ luminosity. The slope of this relation is 0.42 ± 0.02 which can be explained in terms of a distribution of clouds photoionized by the AGN. This relation also indicates that the AGNs have the potential to ionize and heat the gas clouds at a large distance from the nuclei without the aids of outflows and jets for the low-luminosity Seyferts.†

scholarly journals X-ray variability in LINERs

2013 ◽  
Vol 9 (S304) ◽  
pp. 399-402
Author(s):  
Josefa Masegosa ◽  
Lorena Hernández-García ◽  
Isabel Márquez ◽  
Omaira González-Martín
Keyword(s):  
Active Galactic Nuclei ◽  
Time Scales ◽  
Galactic Nuclei ◽  
Spectral Variability ◽  
X Ray ◽  
Line Region ◽  
Variability Pattern ◽  
Long Time ◽  
Public Archives

AbstractOne of the most important features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on time scales from hours to years. Among the AGN family and according to theoretical studies, Low-Ionization Nuclear Emission Line Region (LINER) nuclei would be variable objects on long time scales. Our purpose is to investigate spectral X-ray variability in LINERs and to understand the nature of these kinds of objects, as well as their accretion mechanism. Chandra and XMM–Newton public archives were used to compile X-ray spectra of LINER nuclei at different epochs with time scales of years. To search for variability we fit all the spectra from the same object with a set of models, in order to identify the parameters responsible for the variability pattern. We found that long term spectral variability is very common, with variations mostly related to hard energies (2-10 keV). These variations are due to changes in the soft excess, and/or changes in the absorber, and/or intrinsic variations of the source.

scholarly journals NuSTAR view of Swift/BAT AGN: The R−Γ correlation

2020 ◽  
Vol 640 ◽  
pp. A31 ◽  
Author(s):  
C. Panagiotou ◽  
R. Walter
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Relativistic Velocity ◽  
Strongly Correlated ◽  
Prominent Feature ◽  
Slab Geometry ◽  
Spectral Parameters ◽  
Large Sample ◽  
X Ray ◽  
Exact Shape

Context. The reflection hump is a prominent feature in the hard X-ray spectrum of active galactic nuclei (AGN). Its exact shape and its correlation to other quantities provide valuable information about the inner and outer regions of an AGN. Aims. Our main goal is to study the reflection hump in a large sample of nearby AGN. We aim to investigate the evolution of reflection with absorption and its correlation with the spectral index. Methods. We analysed archived NuSTAR observations of the 70-month BAT catalogue AGN. By performing a detailed spectral analysis, we were able to constrain the spectral parameters and to investigate the reflection emission in a large sample of individual sources. Results. The reflection strength was found to be strongly correlated with the power-law slope in unabsorbed sources, pointing towards disc reflection for these sources. Different possible explanations were tested and the most likely one is that the corona is moving either towards or away from the disc with a moderately relativistic velocity. An R − Γ correlation was not detected for absorbed sources. In addition, these AGN feature harder spectra, suggesting intrinsic differences between the two classes or a slab geometry for the X-ray source.

The X-ray spectra of high-luminosity active galactic nuclei observed by Ginga

1992 ◽  
Vol 389 ◽  
pp. 157 ◽  
Author(s):  
O. R. Williams ◽  
M. J. L. Turner ◽  
G. C. Stewart ◽  
R. D. Saxton ◽  
T. Ohashi ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Luminosity ◽  
X Ray

scholarly journals Compton thick AGN in Chandra sureys

2013 ◽  
Vol 9 (S304) ◽  
pp. 153-154
Author(s):  
Murray Brightman ◽  
Kirpal Nandra
Keyword(s):  
Spectral Analysis ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Rate ◽  
Photoelectric Absorption ◽  
X Ray ◽  
Spectral Signatures ◽  
Spectral Fitting ◽  
Spectral Models ◽  
Uniform Sample

AbstractWe present the results from the X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured, Compton thick (CT, NH > 104 cm−2) sources. Our sample is comprised of 3088 X-ray selected sources, which has a high rate of redshift completeness (97%). The aim is to produce the largest and cleanest uniform sample of these sources from the data as possible. We identify these sources through X-ray spectral fitting, utilising torus spectral models designed for heavily obscured AGN which self consistently include the spectral signatures of heavy absorption, being Compton scattering, photoelectric absorption and iron Kα fluorescence. We identify a total of 163 CT AGN covering an intrinsic 2-10 keV X-ray luminosity range of 102 −3 × 105 erg s−1 and from z = 0.1-7.

scholarly journals Reflection geometries in absorbed and unabsorbed AGN

2019 ◽  
Vol 626 ◽  
pp. A40 ◽  
Author(s):  
C. Panagiotou ◽  
R. Walter
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Accretion Disc ◽  
Spectral Shape ◽  
Active Nucleus ◽  
X Ray ◽  
Main Reflector ◽  
Reflection Component ◽  
Source Geometry ◽  
Key Parameter

Context. The hard X-ray emission of active galactic nuclei (AGN), and in particular, the reflection component, is shaped by the innermost and outer regions of the galactic nucleus. Aims. Our main goal is to investigate the variation of the Compton hump amongst a population of sources and correlate it with other spectral properties to constrain the source geometry. Methods. We studied the NuSTAR hard X-ray spectra of a sample of 83 AGN and performed a detailed spectral analysis of each of them. Based on their spectral shape, we divided the sample into five categories and also studied their stacked spectra. Results. We found a stronger reflection in mildly obscured sources, which verifies the results reported in previous works. In addition, the reflection behaviour, and probably origin, varies with absorption. The accretion disc seems to be the main reflector in unabsorbed sources. A clumpy torus seems to produce most of the reflection in obscured sources. The filling factor of the clouds surrounding the active nucleus is a key parameter that drives the appearance of AGN. Finally, we found that the Fe line and the Compton hump are roughly correlated, as expected.

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