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.

Broad Band X-Ray Telescope observations of NGC 4151 - Iron line diagnostics

1992 ◽  
Vol 401 ◽  
pp. L11 ◽  
Author(s):  
K. A. Weaver ◽  
R. F. Mushotzky ◽  
K. A. Arnaud ◽  
P. J. Serlemitsos ◽  
F. E. Marshall ◽  
...  
Keyword(s):  
Broad Band ◽  
Iron Line ◽  
X Ray ◽  
Ngc 4151

scholarly journals The unusual broad-band X-ray spectral variability of NGC 1313 X-1 seen with XMM–Newton, Chandra, and NuSTAR

2020 ◽  
Vol 494 (4) ◽  
pp. 6012-6029 ◽  
Author(s):  
D J Walton ◽  
C Pinto ◽  
M Nowak ◽  
M Bachetti ◽  
R Sathyaprakash ◽  
...  
Keyword(s):  
Black Hole ◽  
Broad Band ◽  
High Energy ◽  
Accretion Disc ◽  
Continuum Emission ◽  
Spectral Variability ◽  
Temperature Behaviour ◽  
Temperature Relation ◽  
X Ray ◽  
Constant Area

ABSTRACT We present results from the major coordinated X-ray observing programme on the ULX NGC 1313 X-1 performed in 2017, combining XMM–Newton, Chandra, and NuSTAR, focusing on the evolution of the broad-band (∼0.3–30.0 keV) continuum emission. Clear and unusual spectral variability is observed, but this is markedly suppressed above ∼10–15 keV, qualitatively similar to the ULX Holmberg IX X-1. We model the multi-epoch data with two-component accretion disc models designed to approximate super-Eddington accretion, allowing for both a black hole and a neutron star accretor. With regards to the hotter disc component, the data trace out two distinct tracks in the luminosity–temperature plane, with larger emitting radii and lower temperatures seen at higher observed fluxes. Despite this apparent anticorrelation, each of these tracks individually shows a positive luminosity–temperature relation. Both are broadly consistent with L ∝ T4, as expected for blackbody emission with a constant area, and also with L ∝ T2, as may be expected for an advection-dominated disc around a black hole. We consider a variety of possibilities for this unusual behaviour. Scenarios in which the innermost flow is suddenly blocked from view by outer regions of the super-Eddington disc/wind can explain the luminosity–temperature behaviour, but are difficult to reconcile with the lack of strong variability at higher energies, assuming this emission arises from the most compact regions. Instead, we may be seeing evidence for further radial stratification of the accretion flow than is included in the simple models considered, with a combination of winds and advection resulting in the suppressed high-energy variability.

scholarly journals Iron Line Emission from NGC1068

1989 ◽  
Vol 134 ◽  
pp. 167-172
Author(s):  
Katsuji Koyama
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Equivalent Width ◽  
Line Emission ◽  
X Rays ◽  
Iron Line ◽  
X Ray ◽  
Central Engine ◽  
Photon Index ◽  
The Continuum

X-ray emission in the 2–10 keV energy range was observed with the Ginga satellite from the Seyfert 2 galaxy NGC1068. The continuum spectrum can be described by a power-law of photon index about 1.5. An intense iron line at 6.5 keV with an equivalent width of 1.3 keV was clearly noticed. The X-ray flux was about 6 × 10 −12 erg/sec/cm2 or 3 × 1041 erg/sec, assuming a distance of 22 Mpc. The observed spectrum is consistent with the scattering and reprocessing of X-rays by the gas surrounding the central engine. With this picture we estimate that the X-ray flux of the central engine is about 1043 - 1044 erg/sec, a typical value for a Seyfert 1 galaxy.

BeppoSAX observations of the massive X-ray pulsar Cen X-3: Broad-band spectra and iron line diagnostic

2000 ◽  
Vol 25 (3-4) ◽  
pp. 413-416 ◽  
Author(s):  
S. Del Sordo ◽  
D. Dal Fiume ◽  
M. Orlandini ◽  
S. Piraino ◽  
A. Santangelo ◽  
...  
Keyword(s):  
Broad Band ◽  
Iron Line ◽  
X Ray ◽  
Band Spectra

scholarly journals The role of molecular gas in the nuclear regions of IRAS 00183-7111

2018 ◽  
Vol 616 ◽  
pp. A127 ◽  
Author(s):  
I. Ruffa ◽  
C. Vignali ◽  
A. Mignano ◽  
R. Paladino ◽  
K. Iwasawa
Keyword(s):  
Column Density ◽  
Broad Band ◽  
Molecular Gas ◽  
Iron Line ◽  
X Ray ◽  
Diagnostic Diagram ◽  
Ultraluminous Infrared Galaxy ◽  
High Ionization ◽  
Nuclear Environment ◽  
Nuclear Regions

Aims. We present a multi-frequency study of the ultraluminous infrared galaxy (ULIRG) IRAS 00183-7111 (z = 0.327), selected from the Spoon diagnostic diagram as a highly obscured active galactic nucleus (AGN) candidate. ALMA millimetre and X-ray observations are used; the main aim is to verify at what level the molecular gas, traced by the CO, may be responsible for the obscuration observed at X-ray energies. Theory and observations both suggest that galaxy-scale absorption may play a role in the AGN obscuration at intermediate (i.e. Compton-thin) column densities. Methods. We calibrated and analysed ALMA archival Cycle 0 data in two bands (Bands 3 and 6). The X-ray properties of IRAS 00183-7111 were studied by reducing and analysing separately archival Chandra and XMM-Newton data; recently acquired NuSTAR spectra were first examined individually and then added to the Chandra and XMM spectra for the broad-band (0.5 − 24 keV, observed frame) analysis. Results. We derived a molecular gas column density of (8.0 ± 0.9) × 1021 cm−2 from the ALMA CO(1−0) detection, while the best-fit column density of cold gas obtained from X-ray spectral fitting is 6.8−1.5+2.1×1022 cm−. The two quantities suggest that the molecular gas may contribute only a fraction of the AGN obscuration; however, the link between them is not straightforward. The nuclear regions of IRAS 00183-7111 are likely stratified into different layers of matter: one inner and highly ionized by the strong radiation field of the AGN (as inferred from the high-ionization iron line found in the X-ray spectra), and one outer and colder, extending more than 5 kpc from the nucleus (as traced by the molecular gas observed with ALMA). The molecular gas regions also give rise to a vigorous starburst with SFR ~260 ± 28 M⊙ yr−1. The complexity of this nuclear environment makes it difficult to identify the origin of the AGN obscuration given the quality of the data currently available. Higher resolution observations in the millimetre regime are needed to deeply investigate this issue.

scholarly journals Unveiling the Multi-wavelength Phenomenology of Anomalous X-ray Pulsars

2004 ◽  
Vol 218 ◽  
pp. 247-250 ◽  
Author(s):  
GianLuca Israel ◽  
Luigi Stella ◽  
Stefano Covino ◽  
Sergio Campana ◽  
Lorella Angelini ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Broad Band ◽  
Archival Data ◽  
X Rays ◽  
Spectral Variability ◽  
Band Energy ◽  
X Ray ◽  
Pulse Phase ◽  
Multi Wavelength ◽  
Ir Bands

During 2002–2003 the number of IR-identified counterparts to the Anomalous X-ray Pulsars (AXPs) has grown to four (4U 0142+61, IE 2259+586, IE 1048.1−5937 and RXS J170849−400910) out of the six objects (plus two candidates) known in this class. More importantly, some new common characteristics have been identified, such as IR variability, IR flattening in the broad-band energy spectrum, X-ray spectral variability as a function of pulse phase (which are not predicted by the magnetar model), and X-ray bursts (which cannot be explained in terms of standard accretion models). We present the results obtained from an extensive multi-wavelength observational campaign carried out with the NTT and CFHT for the optical/IR bands, and XMM and Chandra (plus BeppoSAX archival data) in X-rays. Based on these results and those reported in the literature, the IR-to-X-ray emission of AXPs is compared.

The X-Ray Afterglow of the Gamma-Ray Burst of 1997 May 8:Spectral Variability and Possible Evidence of an Iron Line

1999 ◽  
Vol 514 (2) ◽  
pp. L73-L77 ◽  
Author(s):  
L. Piro ◽  
E. Costa ◽  
M. Feroci ◽  
F. Frontera ◽  
L. Amati ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Variability ◽  
Iron Line ◽  
Gamma Ray Burst ◽  
X Ray

scholarly journals Detection of a High-Temperature Blackbody Hump in Black Hole Spectra. The strongly redshifted annihilation line

2020 ◽  
Author(s):  
Lev Titarchuk ◽  
Elena Seifina
Keyword(s):  
Black Hole ◽  
High Temperature ◽  
Broad Band ◽  
Spectral Feature ◽  
Line Emission ◽  
Energy Spectra ◽  
Color Temperature ◽  
Iron Line ◽  
Annihilation Line ◽  
X Ray

Abstract We detected a so called high-temperature blackbody (HBB) component, found in the 15 – 40 keV range, in the broad-band X-ray energy spectra of black hole (BH) candidate sources. A detailed study of this spectral feature is presented using data from five of the Galactic BH binaries, Cyg X–1, GX 339–4, GRS 1915+105, SS 433 and V4641 Sgr in the low/hard, intermediate, high/soft and very soft spectral states (LHS, IS, HSS and VSS, respectively) and spectral transitions between them using RXTE, INTEGRAL and BeppoSAX data. In order to fit the broad-band energy spectra of these sources we used an additive XSPEC model, composed of the Comptonization component and the Gaussian line component. In particular, we reveal that the IS spectra have the HBB component which color temperature, kTHBB is in the range of 4.5 – 5.9 keV. This HBB feature has been detected in some spectra of these five sources only in the IS (for the photon index Γ > 1.9) using different X-ray telescopes. We also demonstrate that a timescale of the HBB-feature is of orders of magnitude shorter than the timescale of the iron line and its edge. That leads us to conclude that these spectral features are formed in geometrically different parts of the source and which are not connected to each other. Laurent & Titarchuk (2018) demonstrated a presence of a gravitational redshifted annihilation line emission in a BH using the Monte-Carlo simulations and therefore the observed HBB hump leads us to suggest this feature is a gravitational redshifted annihilation line observed in these black holes.

Polarization properties of iron emission lines as a tool to identify the finite thickness of disks with moderately super-eddington accretion rate

2021 ◽  
pp. 2150074
Author(s):  
Ze-Yuan Tang ◽  
Ye-Fei Yuan
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Accretion Rate ◽  
Finite Thickness ◽  
Polarization Degree ◽  
Iron Line ◽  
Disk Thickness ◽  
X Ray ◽  
X Ray Binaries ◽  
Polarized Radiation

The Fe-K[Formula: see text] fluorescence lines are commonly observed in AGNs and X-ray binaries. The lines are believed to be originated from the reflection of the hard X-ray continuum near the inner-most region of the accretion disks of black holes. The geometry of the accretion disk is usually assumed to be infinitely thin, but this assumption is not appropriate when the accretion rate is moderately super-Eddington. With the increase of the accretion rate, the disk becomes thick, which will significantly affect the properties of the fluorescence lines. For instance, the polarized radiation is strongly depended on the geometry of the accretion disk. In this work, based on the lamp-post model, we study the polarization properties of the relativistic Fe-K[Formula: see text] lines from thick disks in the framework of fully general relativity. We find that with the increase of the disk thickness, the polarization degree (PD) at the blue edge of the iron line increase significantly, and there appears a peak at the profile of the PD of the iron emission line, which at most is one order higher that of the line from the thin disk. Thus, the polarization properties of relativistic broad Fe-K[Formula: see text] lines can be used to as a tool to diagnose the disk thickness.

Water maser emission in hard X-ray selected AGN

2017 ◽  
Vol 13 (S336) ◽  
pp. 96-98
Author(s):  
Francesca Panessa ◽  
Paola Castangia ◽  
Andrea Tarchi ◽  
Loredana Bassani ◽  
Angela Malizia ◽  
...  
Keyword(s):  
Accretion Disks ◽  
Accretion Rate ◽  
Complete Sample ◽  
Absorption Properties ◽  
Maser Emission ◽  
X Ray ◽  
Central Engine ◽  
Inner Region ◽  
Water Maser ◽  
Selection Of

AbstractWater megamaser emission is powerful in tracing the inner region of active nuclei, mapping accretion disks and providing important clues on their absorption properties. From the X-ray spectra of AGN it is possible to estimate the intrinsic power of the central engine and the obscuring column density. The synergy between X-ray and water maser studies allows us to tackle the AGN inner physics from different perspectives. For a complete sample of AGN selected in the 20-40 keV energy range, we have investigated the presence of water maser emission and its connection to the X-ray emission, absorption and accretion rate. The hard X-ray selection of the sample results in a water maser detection rate much higher than those obtained from optically-selected samples.

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