scholarly journals Gamma-ray emission of active galactic nuclei as a signature of relativistic electron-positron beams

1993 ◽  
Vol 404 ◽  
pp. L41 ◽  
Author(s):  
G. Henri ◽  
G. Pelletier ◽  
J. Roland
Keyword(s):  
Active Galactic Nuclei ◽  
Relativistic Electron ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Electron Positron ◽  
Gamma Ray Emission ◽  
Positron Beams

Upper Limits on TeV Gamma-Ray Emission from Active Galactic Nuclei

1995 ◽  
Vol 452 ◽  
pp. 588 ◽  
Author(s):  
A. D. Kerrick ◽  
C. W. Akerlof ◽  
S. Biller ◽  
J. Buckley ◽  
D. A. Carter-Lewis ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Upper Limits ◽  
Gamma Ray Emission

scholarly journals Gamma-Ray Emission from Extragalactic Radio Sources: EGRET Observations of Active Galactic Nuclei

1996 ◽  
Vol 175 ◽  
pp. 277-280
Author(s):  
Peter F. Michelson
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Radio Spectrum ◽  
Active Galaxies ◽  
Emission Characteristics ◽  
Radio Sources ◽  
Emission Models ◽  
Gamma Ray Emission

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory is an imaging high-energy telescope with sensitivity from approximately 20 MeV to 30 GeV. EGRET has observed more than 129 sources during more than 4 years of operation. Among these sources, 51 have been identified with active galaxies. A common characteristic of the AGN sources is that they are all radio-loud, flat radio spectrum sources. Many of them are seen as superluminal radio sources as well. The gamma-ray emission characteristics of these sources are reviewed and some of the proposed emission models are discussed.

scholarly journals Physical Processes in Active Galactic Nuclei

1986 ◽  
Vol 89 ◽  
pp. 324-345
Author(s):  
Roland Svensson
Keyword(s):  
Pair Production ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Rest Mass ◽  
Galactic Nuclei ◽  
Nonthermal Plasma ◽  
Lorentz Factor ◽  
Analytical Models ◽  
Potential Wells ◽  
Electron Positron

AbstractActive galactic nuclei (AGNs) emit continuum radiation evenly spread over up to ten decades in frequency from the radio into the gamma-ray range. Plausible emission mechanisms and their characteristics are reviewed. In the deep potential wells around black holes the mean energy per proton can reach 100 MeV. Part or all of this energy may be channeled to all electrons equally (thermal plasma) or, preferentially, into only a small fraction of the electrons (nonthermal plasma). In the former case thermal Comptonization of soft photons may be the dominant emission mechanism, while in the latter case the synchrotron and the inverse Compton scattering process (synchro-self-Compton) are likely to dominate.When the compactness parameter L (hν≈mc2 )/R. (power L, radius R) exceeds about 1030 ergs cm−1s−1 or L>Lc ≡ 1030R ergs s−1, then electron-positron pair production takes place due to photon-photon interactions causing the source to shroud itself with an electron-positron atmosphere. The efficiency of pair cascades in converting injected energy into electron-positron rest mass can reach levels of about 10% in static pair atmospheres. The emerging radiation is strongly modified by the pair atmosphere causing the spectrum to soften and to have characteristic breaks.For emission coming from a region near the Schwarzschild radius, L>10-3LEdd is sufficient to cause prolific pair production. Radiation pressure then drives a mildly relativistic pair wind with Compton drag limiting the Lorentz factor to be less then 10. The pair rest mass power is at most of the order of Lc.Most results so far on static pair atmospheres and pair winds are either qualitative or based on simple analytical models. Needed numerical treatments of both time dependent and steady radiative transfer of both the continuum and the annihilation line radiation in mildly relativistic flows are relevant not only for AGNs but also for gamma ray bursts and galactic black hole sources.

scholarly journals Correlated neutrino and gamma-ray emission from Active Galactic Nuclei - an estimation

2012 ◽  
Vol 355 ◽  
pp. 012039 ◽  
Author(s):  
M Doert ◽  
J K Becker ◽  
F Halzen ◽  
A O'Murchadha ◽  
W Rhode
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Gamma Ray Emission

scholarly journals Radio and Gamma-ray emission in nearby BL Lacs

2013 ◽  
Vol 9 (S304) ◽  
pp. 200-203 ◽  
Author(s):  
G. Giovannini ◽  
E. Liuzzo ◽  
B. Boccardi ◽  
M. Giroletti
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Scale Structure ◽  
Bl Lac Objects ◽  
Long Baseline ◽  
Γ Ray ◽  
Gamma Ray Emission ◽  
Very Long Baseline Array ◽  
Bl Lacs

AbstractThe advent of Fermi is changing our understanding on the radio and γ-ray emission in active galactic nuclei. Unlike pre-Fermi ideas, BL Lac objects are found to be the most abundant emitters in the γ-ray band. However, since they are relatively weak radio sources, most of their parsec-scale structure and their multifrequency properties are poorly understood and/or have not been investigated in a systematic fashion. Here we are analyzing the radio and γ-ray emission properties of a sample of 42 BL Lacs selected with no constraint on their radio and γ-ray emission. Thanks to new Very Long Baseline Array observations at 8 and 15 GHz for the whole sample, we discuss their parsec-scale structure. Parsec-scale radio emission is observed in the majority of the sources at both frequencies. The comparison between our results in radio and gamma-ray bands points out the presence of a large number of faint BL Lacs showing “non-classical” properties such as low source compactness, low core dominance, no gamma-ray emission.

scholarly journals Magnetospheric Gamma-Ray Emission in Active Galactic Nuclei

2018 ◽  
Vol 852 (2) ◽  
pp. 112 ◽  
Author(s):  
Grigorios Katsoulakos ◽  
Frank M. Rieger
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Gamma Ray Emission
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