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.

scholarly journals Evidence for Strong Gravity in the AGN Plasmas

1998 ◽  
Vol 188 ◽  
pp. 141-144
Author(s):  
K. Iwasawa
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Iron Line ◽  
X Ray ◽  
Strong Gravity

X-ray spectroscopy of the broad iron line has revealed some relativistic effects caused by strong gravity about a black hole in active galactic nuclei (AGN). Recent results from ASCA observations of AGNs are reviewed.

scholarly journals Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation

2014 ◽  
Vol 447 (2) ◽  
pp. 1692-1704 ◽  
Author(s):  
Qi-Xiang Yang ◽  
Fu-Guo Xie ◽  
Feng Yuan ◽  
Andrzej A. Zdziarski ◽  
Marek Gierliński ◽  
...  
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Photon Index ◽  
X Ray Binaries

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.

scholarly journals A NuSTAR census of coronal parameters in Seyfert galaxies

2018 ◽  
Vol 614 ◽  
pp. A37 ◽  
Author(s):  
A. Tortosa ◽  
S. Bianchi ◽  
A. Marinucci ◽  
G. Matt ◽  
P. O. Petrucci
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Optical Depth ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Black Hole Mass ◽  
Significance Level ◽  
X Ray ◽  
Photon Index ◽  
Hot Corona

Context. We discuss the results of the hot corona parameters of active galactic nuclei (AGN) that have been recently measured with NuSTAR. The values taken from the literature of a sample of 19 bright Seyfert galaxies are analysed. Aims. The aim of this work is to look for correlations between coronal parameters, such as the photon index and cut-off energy (when a phenomenological model is adopted) or the optical depth and temperature (when a Comptonization model is used), and other parameters of the systems, such as the black hole mass or the Eddington ratio. Methods. We analysed the coronal parameters of the 19 unobscured, bright Seyfert galaxies that are present in the Swift/BAT 70-month catalogue and that have been observed by NuSTAR, alone or simultaneously with others X-ray observatories, such as Swift, Suzaku, or XMM-Newton. Results. We found an anti-correlation with a significance level >98% between the coronal optical depth and the coronal temperature of our sample. On the other hand, no correlation between the above parameters and the black hole mass, the accretion rate, and the intrinsic spectral slope of the sources is found.

scholarly journals The WISSH quasars project

2020 ◽  
Vol 635 ◽  
pp. L5 ◽  
Author(s):  
L. Zappacosta ◽  
E. Piconcelli ◽  
M. Giustini ◽  
G. Vietri ◽  
F. Duras ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Accretion Disc ◽  
Broad Line ◽  
Absorption Column ◽  
Mid Infrared ◽  
X Ray ◽  
Similar Dependence ◽  
Photon Index ◽  
Nuclear Regions

Hyper-luminous quasars (Lbol ≳ 1047 erg s−1) are ideal laboratories to study the interaction and impact of the extreme radiative field and the most powerful winds in the active galactic nuclei (AGN) nuclear regions. They typically exhibit low coronal X-ray luminosity (LX) compared to the ultraviolet (UV) and mid-infrared (MIR) radiative outputs (LUV and LUV); a non-negligible fraction of them report even ∼1 dex weaker LX compared to the prediction of the well established LX–LUV and LX–LUV relations followed by the bulk of the AGN population. In our WISE/SDSS-selected Hyper-luminous (WISSH) z = 2 − 4 broad-line quasar sample, we report on the discovery of a dependence between the intrinsic 2–10 keV luminosity (L2 − 10) and the blueshifted velocity of the CIV emission line (vCIV) that is indicative of accretion disc winds. In particular, sources with the fastest winds (vCIV ≳ 3000 km s−1) possess ∼0.5–1 dex lower L2 − 10 than sources with negligible vCIV. No similar dependence is found on LUV, LUV, Lbol, the photon index, or the absorption column density. We interpret these findings in the context of accretion disc wind models. Both magnetohydrodynamic and line-driven models can qualitatively explain the reported relations as a consequence of X-ray shielding from the inner wind regions. In case of line-driven winds, the launch of fast winds is favoured by a reduced X-ray emission, and we speculate that these winds may play a role in directly limiting the coronal hard X-ray production.

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 The shape of Fe Kα line emitted from relativistic accretion disc around AGN black holes

2018 ◽  
Vol 33 (34) ◽  
pp. 1845016
Author(s):  
Milan Milošević ◽  
Miika A. Pursiainen ◽  
Predrag Jovanović ◽  
Luka Č. Popović
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Outer Radius ◽  
Accretion Disc ◽  
Text Line ◽  
Line Profiles ◽  
Massive Black Hole ◽  
X Ray

The relativistically broadened Fe K[Formula: see text] line, originating from the accretion disc in a vicinity of a super massive black hole, is observed in only less than 50% of type 1 Active Galactic Nuclei (AGN). In this study, we investigate could this lack of detections be explained by the effects of certain parameters of the accretion disc and black hole, such as the inclination, the inner and outer radius of disc and emissivity index. In order to determine how these parameters affect the Fe K[Formula: see text] line shape, we simulated about 60,000 Fe K[Formula: see text] line profiles emitted from the relativistic disc. Based on simulated line profiles, we conclude that the lack of the Fe K[Formula: see text] line detection in type 1 AGN could be caused by the specific emitting disc parameters, but also by the limits in the spectral resolution and sensitivity of the X-ray detectors.

scholarly journals Relativistic Fe Kα line in the composite X-ray spectra of radio-loud active galactic nuclei

2019 ◽  
Vol 488 (3) ◽  
pp. 4378-4388
Author(s):  
Jingwei Hu ◽  
Zhu Liu ◽  
Chichuan Jin ◽  
Weimin Yuan
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Precise Measurement ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Line Profiles ◽  
X Ray ◽  
Wide Range ◽  
Average Spin ◽  
Spectral Profiles

ABSTRACT While a broad Fe Kα emission line is generally found in the X-ray spectra of radio quiet (RQ) active galactic nuclei (AGNs), this feature, commonly thought to be broadened by the relativistic effects near the central black hole, appears to be rare in their radio loud (RL) counterparts. In this paper, we carry out a detailed study of the ensemble property of the X-ray spectra, focusing on the Fe line, of 97 RL AGNs by applying the spectral stacking method to the spectra obtained with XMM–Newton. For comparison, the same analysis is also performed for 193 RQ AGNs. Both a narrow and a broad component of the Fe Kα line are detected at high significance in the stacked spectra of both samples. The broad lines can be well fitted with relativistically broadened line profiles. Our results suggest that, as in their RQ counterparts, a relativistic Fe line component is commonly present in RL AGNs, though it may not be detected unambiguously in individual objects with spectra of relatively low signal to noise. We try to constrain the average spin of the black holes for both the RL and RQ AGN samples by modelling their composite Fe line spectral profiles with relativistic disc line models. For the RL sample, the average spin is loosely constrained and a wide range is allowed except for very fast spins (<0.78, 90 per cent confidence), while for the RQ sample, it is constrained to be low or moderate (<0.24). We conclude that the more precise measurement of the black hole spins in RL AGNs has to await for the advent of future high-throughput X-ray telescopes.

scholarly journals Estimating the size of X-ray lamppost coronae in active galactic nuclei

2020 ◽  
Vol 644 ◽  
pp. A132
Author(s):  
F. Ursini ◽  
M. Dovčiak ◽  
W. Zhang ◽  
G. Matt ◽  
P.-O. Petrucci ◽  
...  
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Stable Circular Orbit ◽  
Disc Area ◽  
Higher Spin ◽  
Photon Index ◽  
Innermost Stable Circular Orbit ◽  
Eddington Limit

Aims. We report estimates of the X-ray coronal size of active galactic nuclei in the lamppost geometry. In this commonly adopted scenario, the corona is assumed for simplicity to be a point-like X-ray source located on the axis of the accretion disc. However, the corona must intercept a number of optical/UV seed photons from the disc consistent with the observed X-ray flux, which constrains its size. Methods. We employ a relativistic ray-tracing code, originally developed by Dovčiak and Done, that calculates the size of a Comptonizing lamppost corona illuminated by a standard thin disc. We assume that the disc extends down to the innermost stable circular orbit of a non-spinning or a maximally spinning black hole. We apply this method to a sample of 20 Seyfert 1 galaxies using simultaneous optical/UV and X-ray archival data from XMM-Newton. Results. At least for the sources accreting below the Eddington limit, we find that a Comptonizing lamppost corona can generally exist, but with constraints on its size and height above the event horizon of the black hole depending on the spin. For a maximally spinning black hole, a solution can almost always be found at any height, while for a non-spinning black hole the height must generally be higher than 5 gravitational radii. This is because, for a given luminosity, a higher spin implies more seed photons illuminating the corona, which is due to a larger and hotter inner disc area. The maximal spin solution is favoured, as it predicts an X-ray photon index in better agreement with the observations.

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