The Average X Ray Gamma Ray Spectra Of Seyfert Galaxies From Ginga And Osse And The Origin Of The Cosmic X Ray Background PDF Download
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Total Pages | : 12 |
Release | : 1995 |
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Download The Average X-Ray/Gamma-Ray Spectra of Seyfert Galaxies From Ginga and OSSE and the Origin of the Cosmic X-Ray Background Book in PDF, ePub and Kindle
We have obtained the first average 2-500 keV spectra of Seyfert galaxies, using the data from Ginga and GRO OSSE. Our sample contains 3 classes of objects with markedly different spectra: radio-quiet Seyfert 1s and 2s, and radio-loud Seyfert 1s. The average radio-quiet Seyfert 1 spectrum is well- fitted by a power law continuum with the energy spectral index approximately equal 0.9, a Compton reflection component corresponding to a ~ 2x covering solid angle, and ionized absorption. There is a high-energy cutoff in the incident power law continuum: the e-folding energy is E(sub c) approximately equal 0.6 (sup +0.8, sub -0.3)MeV. The simplest model that describes this spectrum is Comptonization in a relativistic optically-thin thermal corona above the surface of an accretion disk. Radio-quiet Seyfert 2s show strong neutral absorption, and there is an indication that their X-ray power laws are intrinsically harder, although the Seyfert 1 spectrum with = 0.9 and strong reflection cannot be ruled out by the data. Finally, the radio-loud Seyfert spectrum has alpha approximately equal 0.7, moderate neutral absorption, E (sub c) = 0.4(sup +0.7, sub -0.2) MeV, and no or little Compton reflection. This is incompatible with the radio-quiet Seyfert 1 spectrum, and probably indicating that the X-rays are beamed away from the accretion disk in these objects. The average spectra of Seyferts integrated over redshift with a power law evolution can explain the hard X-ray spectrum of the cosmic background. The hump at ~ 30 keV in that spectrum is due to the dominant contribution of Seyfert 2s.
Author | : Ajit K. Kembhavi |
Publisher | : Cambridge University Press |
Total Pages | : 488 |
Release | : 1999-03-11 |
Genre | : Science |
ISBN | : 9780521479899 |
Download Quasars and Active Galactic Nuclei Book in PDF, ePub and Kindle
The latest observations and theoretical models are combined in this clear, pedagogic textbook for advanced undergraduates and graduate students.
Author | : Volker Beckmann |
Publisher | : John Wiley & Sons |
Total Pages | : 390 |
Release | : 2013-08-29 |
Genre | : Science |
ISBN | : 352766680X |
Download Active Galactic Nuclei Book in PDF, ePub and Kindle
Active Galactic Nuclei This AGN textbook gives an overview on the current knowledge of the Active Galacitc Nuclei phenomenon. The spectral energy distribution will be discussed, pointing out what can be observed in different wavebands. The different physical models are presented together with formula important for the understanding of AGN physics. Furthermore, the authors discuss the AGN with respect to its environment, host galaxy, feedback in galaxies and in clusters of galaxies, variability, etc. and finally the cosmological evolution of the AGN phenomenon. This book includes phenomena based on new results in the X-Ray and gamma-ray domain from new telescopes such as Chandra, XMM-Newton, the Fermi Gamma-Ray Space Telescope, and the VHE regime not mentioned so far in AGN books. Those and other new developments as well as simulations of AGN merging events and formations, enabled through latest super-computing capabilities. From the contents: The observational picture of AGN Radiative processes The central engine AGN types and unification AGN through the electromagnetic spectrum AGN variability Environment Quasars and cosmology Formation, evolution and the ultimate fate of AGN What we do not know (yet)
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Total Pages | : 624 |
Release | : 1996 |
Genre | : Astronomy |
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Download Referativnyĭ zhurnal Book in PDF, ePub and Kindle
Author | : Kimberly Weaver |
Publisher | : |
Total Pages | : 336 |
Release | : 1993 |
Genre | : Astronomical spectroscopy |
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Download The Complex Broad-band X-ray Spectra of Seyfert Galaxies Book in PDF, ePub and Kindle
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Total Pages | : 14 |
Release | : 2013 |
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Download Probing the Cosmic X-ray and MeV Gamma-ray Background Radiation Through the Anisotropy Book in PDF, ePub and Kindle
While the cosmic soft X-ray background is very likely to originate from individual Seyfert galaxies, the origin of the cosmic hard X-ray and MeV gamma-ray background is not fully understood. It is expected that Seyferts including Compton thick population may explain the cosmic hard X-ray background. At MeV energy range, Seyferts having non-thermal electrons in coronae above accretion disks or MeV blazars may explain the background radiation. We propose that future measurements of the angular power spectra of anisotropy of the cosmic X-ray and MeV gamma-ray backgrounds will be key to deciphering these backgrounds and the evolution of active galactic nuclei (AGNs). As AGNs trace the cosmic large-scale structure, spatial clustering of AGNs exists. We show that e-ROSITA will clearly detect the correlation signal of unresolved Seyferts at 0.5-2 keV and 2-10 keV bands and will be able to measure the bias parameter of AGNs at both bands. Once future hard X-ray all sky satellites achieve a sensitivity better than 10-12 erg cm-2 s-1 at 10-30 keV or 30-50 keV--although this is beyond the sensitivities of current hard X-ray all sky monitors--angular power spectra will allow us to independently investigate the fraction of Compton-thick AGNs in all Seyferts. We also find that the expected angular power spectra of Seyferts and blazars in the MeV range are different by about an order of magnitude, where the Poisson term, so-called shot noise, is dominant. Current and future MeV instruments will clearly disentangle the origin of the MeV gamma-ray background through the angular power spectrum.
Author | : H. Bradt |
Publisher | : Springer Science & Business Media |
Total Pages | : 323 |
Release | : 2012-12-06 |
Genre | : Science |
ISBN | : 9401025851 |
Download X- and Gamma-Ray Astronomy Book in PDF, ePub and Kindle
The IAU Symposium No. 55 on 'X-Ray and Gamma-Ray Astronomy' has occurred, not entirely by coincidence, at an important moment in the development of these new branches of observational astronomy. In X-ray astronomy the data from the first X-ray observatory UHURU have contributed to a new view of the X-ray sky and a new conception of the nature and properties of galactic and extragalactic X-ray sources. In gamma-ray astronomy the exciting and often controversial nature of the results underlines the importance of the forthcoming launch of SAS-B, the first orbiting y-ray observatory. As Bruno Rossi reminds us (p. I), the Symposium occurred almost exactly ten years after the first detection of the X-ray star Sco X-I. During this time we have moved from the detection of a handful of the nearest and brightest sources to the detailed study of the nature of stellar sources in the farthest reaches of our own galaxy and in external galaxies of the local group. The detection of pulsating X-ray sources in bi nary systems permits the measurement of pulsation periods, and orbital parameters with precisions comparable to any yet achieved with traditional observational techniques. The strong indications that most X-ray sources are extremely compact objects give us confidence that X-ray astronomy will playa significant and possibly decisive role in the study of stars near the end point of stellar evolution.
Author | : Carl E. Fichtel |
Publisher | : |
Total Pages | : 388 |
Release | : 1997 |
Genre | : Gamma ray astronomy |
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Download Gamma-ray Astrophysics Book in PDF, ePub and Kindle
Author | : United States. National Aeronautics and Space Administration |
Publisher | : |
Total Pages | : 44 |
Release | : 1990 |
Genre | : Gamma ray astronomy |
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Download The Gamma-Ray Observatory Book in PDF, ePub and Kindle
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Total Pages | : 32 |
Release | : 1996 |
Genre | : Gamma ray astronomy |
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Download Gamma-ray Astronomy in the Compton Era Book in PDF, ePub and Kindle