scholarly journals A comprehensive analysis of the hard X-ray spectra of bright Seyfert galaxies

2016 ◽  
Vol 458 (3) ◽  
pp. 2454-2475 ◽  
Author(s):  
P. Lubiński ◽  
V. Beckmann ◽  
L. Gibaud ◽  
S. Paltani ◽  
I. E. Papadakis ◽  
...  
Keyword(s):  
Seyfert Galaxies ◽  
Comprehensive Analysis ◽  
X Ray

scholarly journals Active Nuclei and Redshift Problems

1983 ◽  
Vol 6 ◽  
pp. 531-533
Author(s):  
Geoffrey Burbidge
Keyword(s):  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Radio Sources ◽  
Powerful Radio ◽  
Radiation Mechanism ◽  
X Ray ◽  
Major Interest ◽  
Relativistic Particles

More than 20 years ago V. A. Ambartsumian proposed that much of the activity in galaxies was dominated and even generated by their nuclei. Subsequent observational work in radio, optical and x-ray frequencies has borne out his prophecy, and major interest has centered about the nature of the machine in the galactic nucleus. The major characteristic of this machine is that it releases energy rapidly and often spasmodically by processes which are not thermonuclear in origin.The original studies which led to the conclusion that nuclei were all important were observations of the powerful radio sources and Seyfert galaxies, and evidence for the ejection of gas from galaxies of many types. The realization that the synchrotron mechanism was the dominant radiation mechanism and the later studies of Compton radiation were fundamental in leading to the conclusion that large fluxes of relativistic particles must be generated in galactic nuclei.

scholarly journals Measuring the supermassive black hole parameters with space missions

2006 ◽  
Vol 2 (S238) ◽  
pp. 475-476
Author(s):  
Alexander F. Zakharov
Keyword(s):  
Black Hole ◽  
Spectral Line ◽  
Accretion Disks ◽  
Seyfert Galaxies ◽  
Emission Lines ◽  
X Ray ◽  
Line Shapes ◽  
Supermassive Black Hole ◽  
Broad Emission ◽  
Different Types

AbstractRecent X-ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Recently Müller & Camenzind (2004) classified different types of spectral line shapes and described their origin. Zakharov (2006b) clarified their conclusions about an origin of doubled peaked and double horned line shapes in the framework of a radiating annulus model and discussed s possibility to evaluate black hole parameters analyzing spectral line shapes.

scholarly journals On the Geometry of the X-Ray–emitting Region in Seyfert Galaxies

1995 ◽  
Vol 449 (1) ◽  
Author(s):  
Boris E. Stern, ◽  
Juri Poutanen, ◽  
Roland Svensson, ◽  
Marek Sikora, ◽  
Mitchell C. Begelman
Keyword(s):  
Seyfert Galaxies ◽  
X Ray

The Effect of Different Methods to Pretreat Reed Pulp on the Crystallinity of Microcrystalline Cellulose

2014 ◽  
Vol 1056 ◽  
pp. 12-15 ◽  
Author(s):  
Wen Long Zhang ◽  
Wen Long Zhao ◽  
Ya Jie Dai
Keyword(s):  
Crystallite Size ◽  
Microcrystalline Cellulose ◽  
Average Crystallite Size ◽  
Comprehensive Analysis ◽  
Raw Material ◽  
Type I ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dimethyl Acetamide ◽  
Crystal Type

Reed Pulp was Raw Material that Pretreated by Four Methods {ultrasonic, Microwave, N, N-Dimethyl Acetamide (DMAc) and Tetrahydrofuran (THF)}. Reed Microcrystalline Cellulose (MCC) was Prepared by the Dilute Hydrochloric Acid Hydrolysis from Pretreated Reed Pulp. the Influences of Pretreatment Methods on Crystalline Type, Crystallinity and Crystallite Size of MCC were Investigated by X-Ray Diffraction (XRD). the Results Showed that the Crystallinity of MCC with Four Pretreatment Methods was 68.45%, 62.28%, 63.21% and 69.56%, Respectively. the Average Crystallite Size of MCC Prepared by Hydrolysis after Pretreated by Dmac was the Largest. whereas, the Crystal Type of MCC was Not Changed, it was still the Cellulose Type I. Comprehensive Analysis Indicated that the Effects of MCC Prepared by Hydrolysis after Pretreated by Ultrasonic were the Best.

NGC 4151 and MCG 8-11-11: Two X-Ray Seyfert Galaxies with Strong Soft γ-Ray Emission

1981 ◽  
pp. 107-112
Author(s):  
L. Bassani ◽  
R. C. Butler ◽  
A. J. Dean ◽  
G. Di Cocco ◽  
N. A. Dipper ◽  
...  
Keyword(s):  
Seyfert Galaxies ◽  
X Ray ◽  
Ngc 4151 ◽  
Γ Ray

X-Ray Properties of Liners and Low Luminosity Seyfert Galaxies Observed with ASCA

1998 ◽  
pp. 444-445 ◽  
Author(s):  
Y. Terashima ◽  
H. Kunieda ◽  
P. J. Serlemitsos ◽  
A. Ptak
Keyword(s):  
Seyfert Galaxies ◽  
X Ray

scholarly journals X-Ray Aspects of the IRAS Galaxies

1998 ◽  
Vol 188 ◽  
pp. 145-148
Author(s):  
E.J.A. Meurs
Keyword(s):  
Stellar Evolution ◽  
Seyfert Galaxies ◽  
Temporal Variations ◽  
Spectral Studies ◽  
X Rays ◽  
X Ray ◽  
Active Core

Several IRAS galaxies have been detected at X-rays, with a variety of satellite observatories. About half of these are classified optically as Seyfert galaxies. Among those not (convincingly) classified as AGN, many have X-ray luminosities for which stellar evolution products offer convenient explanations. Some non-active IRAS galaxies display anomalously high levels of X-ray emission for which several conceivable origins are investigated: optical misclassification, X-ray misidentification, hidden AGN, incidental activity, starburst, environmental sources. X-ray spectral studies and temporal variations constitute important tools for further investigation, for instance to assess the strength of a starburst or to establish signatures of an active core.

scholarly journals Identification of AGN in the XMM-Newton X-ray survey of the SMC

2019 ◽  
Vol 622 ◽  
pp. A29 ◽  
Author(s):  
Chandreyee Maitra ◽  
Frank Haberl ◽  
Valentin D. Ivanov ◽  
Maria-Rosa L. Cioni ◽  
Jacco Th. van Loon
Keyword(s):  
Near Infrared ◽  
Spectral Characteristics ◽  
Selection Criterion ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Mid Infrared ◽  
X Ray ◽  
Stellar Density ◽  
Narrow Emission

Context. Finding active galactic nuclei (AGN) behind the Magellanic Clouds (MCs) is difficult because of the high stellar density in these fields. Although the first AGN behind the Small Magellanic Cloud (SMC) were reported in the 1980s, it is only recently that the number of AGN known behind the SMC has increased by several orders of magnitude. Aims. The mid-infrared colour selection technique has proven to be an efficient means of identifying AGN, especially obscured sources. The X-ray regime is complementary in this regard and we use XMM-Newton observations to support the identification of AGN behind the SMC. Methods. We present a catalogue of AGN behind the SMC by correlating an updated X-ray point-source catalogue from our XMM-Newton survey of the SMC with previously identified AGN from the literature as well as a list of candidates obtained from the ALLWISE mid-infrared colour-selection criterion. We studied the properties of the sample with respect to their redshifts, luminosities, and X-ray spectral characteristics. We also identified the near-infrared counterpart of the sources from the VISTA observations. Results. The redshift and luminosity distributions of the sample (where known) indicate that we detect sources ranging from nearby Seyfert galaxies to distant and obscured quasars. The X-ray hardness ratios are compatible with those typically expected for AGN, and the VISTA colours and variability are also consistent with AGN. A positive correlation was observed between the integrated X-ray flux (0.2–12 keV) and the ALLWISE and VISTA magnitudes. We further present a sample of new candidate AGN and candidates for obscured AGN. Together these make an interesting subset for further follow-up studies. An initial spectroscopic follow-up of 6 out of the 81 new candidates showed that all six sources are active galaxies, although two have narrow emission lines.

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