scholarly journals Compton reflection and iron fluorescence in BeppoSAX observations of Seyfert type 1 galaxies

2002 ◽  
Vol 389 (3) ◽  
pp. 802-811 ◽  
Author(s):  
G. C. Perola ◽  
G. Matt ◽  
M. Cappi ◽  
F. Fiore ◽  
M. Guainazzi ◽  
...  
Keyword(s):  
Seyfert Type

scholarly journals The Extragalactic X-Ray and γ-ray Backgrounds

1990 ◽  
Vol 139 ◽  
pp. 345-356
Author(s):  
G. Setti
Keyword(s):  
Big Bang ◽  
Prima Facie ◽  
Baryon Density ◽  
Primordial Nucleosynthesis ◽  
X Ray ◽  
Γ Ray ◽  
X Ray Background ◽  
Seyfert Type ◽  
Number Of Authors

The long-standing problem of the origin of the extragalactic X-ray background (XRB) is reviewed. Although the shape of the spectrum in the 3–100 keV interval is suggestive of an optically thin bremsstrahlung at ~ 40 keV, the interpretation in terms of a hot intergalactic gas (IGG) requires a rather extreme energy supply and a gas density conflicting with the baryon density upper limit derived from primordial nucleosynthesis calculations in the standard hot big-bang model. A summary discussion of the estimated contributions from the integrated X-ray emission of known classes of extragalactic discrete sources at a reference energy of 2 keV is given. Although these estimates are still uncertain, the subtraction of a “minimum” contribution drastically modifies the 40 keV thermal shape, which is the prima facie evidence of a hot IGG. AGNs are the main contributors. Low luminosity AGNs (Seyfert type 1 nuclei) at redshift z = 1 − 2 may in fact saturate the 2 keV XRB, but their observed hard X-ray spectra are on the average unlike (much too steep) that of the XRB. This has led a number of authors to postulate new classes of sources and some exotic models which are briefly summarized. However, if a recently proposed unified scheme of AGNs holds, then the bulk of the XRB intensity can be explained independently of the observed spectral differences and with a mild cosmological evolution. The origin of the extragalactic γ-ray background is briefly commented upon in the concluding remarks.

scholarly journals The host galaxies of Seyfert type 1 nuclei

1994 ◽  
Vol 266 (4) ◽  
pp. 953-971 ◽  
Author(s):  
J. K. Kotilainen ◽  
M. J. Ward
Keyword(s):  
Host Galaxies ◽  
Seyfert Type

Seyfert Type 1 galaxies observed with the HEAO 1 scanning modulation collimator

1980 ◽  
Vol 235 ◽  
pp. 355 ◽  
Author(s):  
R. G. Dower ◽  
H. V. Bradt ◽  
R. E. Doxsey ◽  
M. D. Johnston ◽  
R. E. Griffiths
Keyword(s):  
Modulation Collimator ◽  
Seyfert Type

scholarly journals Determination of the Magnetic Field Strength and Geometry in the Accretion Disks of AGNs by Optical Spectropolarimetry

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 202
Author(s):  
Mikhail Piotrovich ◽  
Stanislava Buliga ◽  
Tinatin Natsvlishvili
Keyword(s):  
Magnetic Field ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Degree Of Polarization ◽  
Special Astrophysical Observatory ◽  
Average Value ◽  
Seyfert Type ◽  
The Magnetic Field

Based on the spectropolarimetric data of 33 Seyfert type 1 galaxies observed with the BTA-6m telescope of the Special Astrophysical Observatory, we estimated the magnetic field values at the event horizon of the supermassive black hole BH and the exponents of the power-law dependence s of the magnetic field on the radius. We used the model of optically thick geometrically thin Shakura–Sunyaev accretion disk. The average value of logBH[G] was found to be ∼4, which is in good agreement with the results obtained by other methods. The average value of s is s≈1.7, and its distribution maximum span is in the range od 1.85<s<2.0. This is a rather interesting result, since s=5/4 is usually adopted in calculations for Shakura–Sunyaev accretion disks. In addition, for two objects PG 1545+210 and 2MASX J06021107+2828382, the measured degree of polarization is greater than the maximum possible value at the angle between the line of sight and the axis of the accretion disk i=45°. It was concluded that for these objects the angle should be closer to i=60°.

Extragalactic X-ray observations - The 2A catalogue and supplementary results from the Ariel 5 sky survey

1979 ◽  
Vol 366 (1726) ◽  
pp. 375-390 ◽  
Keyword(s):  
Radio Galaxies ◽  
Status Report ◽  
Galactic Latitude ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Major Class ◽  
Sky Survey ◽  
Emission Line Galaxies ◽  
Seyfert Type

A status report is given on the Ariel 5 sky survey for X -ray sources at galactic latitude | b | ≽ 10°. The operation of the sky survey instrument (s. s. i.) is briefly reviewed and the production of the recently published 2A catalogue of X -ray sources is described. A remarkably high percentage ( ca . 75%) of the 105 sources in the 2A catalogue have now been identified with extragalactic, or, in a few cases, galactic, counterparts, and this is attributed to the improved location of sources (cf. the earlier 3U catalogue), and the strong correlation with optically bright or outstanding objects. The 2A catalogue and subsequent studies have established active galaxies, especially of the Seyfert type 1, to be a major class of powerful X -ray emitter. Present members of this class, which also includes a number of emission line galaxies, radio galaxies and quasars, are listed and their basic X -ray properties reviewed. The second major class of extragalactic X -ray source, clusters of galaxies, first established with the Uhuru satellite, has been substantially extended by Ariel 5. This work also is briefly reviewed. Finally, additional X -ray data from the s. s. i. (still operative) is being used to revise and add to the 2A catalogue. Several examples of this more recent work are given, together with an estimate of the expected content of the final s. s. i. catalogue when the mission is terminated (now planned for October 1979).

Crystalloid Inclusions in Hepatocyte Mitochondria and Their Similarity to Cytoplasmic Crystalloids

1974 ◽  
Vol 32 ◽  
pp. 198-199
Author(s):  
Odell T. Minick ◽  
Hidejiro Yokoo
Keyword(s):  
Liver Disease ◽  
Alcoholic Liver Disease ◽  
Special Interest ◽  
Structural Variations ◽  
Mitochondrial Alterations ◽  
The Matrix ◽  
Crystalloid Inclusions ◽  
Liver Biopsies

Mitochondrial alterations were studied in 25 liver biopsies from patients with alcoholic liver disease. Of special interest were the morphologic resemblance of certain fine structural variations in mitochondria and crystalloid inclusions. Four types of alterations within mitochondria were found that seemed to relate to cytoplasmic crystalloids.Type 1 alteration consisted of localized groups of cristae, usually oriented in the long direction of the organelle (Fig. 1A). In this plane they appeared serrated at the periphery with blind endings in the matrix. Other sections revealed a system of equally-spaced diagonal lines lengthwise in the mitochondrion with cristae protruding from both ends (Fig. 1B). Profiles of this inclusion were not unlike tangential cuts of a crystalloid structure frequently seen in enlarged mitochondria described below.

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

Direct structure images of 30° partial dislocation cores in silicon

1987 ◽  
Vol 45 ◽  
pp. 242-243
Author(s):  
J. C. Barry ◽  
H. Alexander
Keyword(s):  
Dislocation Core ◽  
Preparation Technique ◽  
Burgers Vector ◽  
Vector Type ◽  
Sample Preparation Technique ◽  
Lattice Images ◽  
Dislocation Core Structure ◽  
Type Lattice ◽  
Direct Inspection

Dislocations in silicon produced by plastic deformation are generally dissociated into partials. 60° dislocations (Burgers vector type 1/2[101]) are dissociated into 30°(Burgers vector type 1/6[211]) and 90°(Burgers vector type 1/6[112]) dislocations. The 30° partials may be either of “glide” or “shuffle” type. Lattice images of the 30° dislocation have been obtained with a JEM 100B, and with a JEM 200Cx. In the aforementioned experiments a reasonable but imperfect match was obtained with calculated images for the “glide” model. In the present experiment direct structure images of 30° dislocation cores have been obtained with a JEOL 4000EX. It is possible to deduce the 30° dislocation core structure by direct inspection of the images. Dislocations were produced by compression of single crystal Si (sample preparation technique described in Alexander et al.).

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