scholarly journals Modification of the gamma-ray spectra from active galaxies by soft radiation of transiting luminous stars

2021 ◽  
Author(s):  
Wlodek Bednarek ◽  
Julian Sitarek
Keyword(s):  
Gamma Ray ◽  
Active Galaxies ◽  
Soft Radiation

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 Active Galaxies and the Diffuse Gamma-Ray Background

1984 ◽  
Vol 422 (1 Eleventh Texa) ◽  
pp. 358-358
Author(s):  
D. KAZANAS ◽  
R. J. PROTHEROE
Keyword(s):  
Gamma Ray ◽  
Active Galaxies

Gamma-ray emissions from active galaxies

1989 ◽  
Vol 158 (1) ◽  
pp. 117-121
Author(s):  
M. M. Lau ◽  
E. C. M. Young ◽  
K. N. Yu
Keyword(s):  
Gamma Ray ◽  
Active Galaxies

High-Energy Gamma-Ray Emission from Active Galaxies: EGRET Observations and Their Implications

1995 ◽  
Vol 440 ◽  
pp. 525 ◽  
Author(s):  
C. von Montigny ◽  
D. L. Bertsch ◽  
J. Chiang ◽  
B. L. Dingus ◽  
J. A. Esposito ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Active Galaxies ◽  
High Energy Gamma ◽  
Energy Gamma ◽  
Gamma Ray Emission

scholarly journals High-Energy Gamma-Ray Observations of Active Galaxies

1994 ◽  
Vol 142 ◽  
pp. 917-922
Author(s):  
Carl E. Fichtel
Keyword(s):  
Gamma Ray ◽  
Seyfert Galaxies ◽  
High Energy ◽  
Active Galaxies ◽  
Bl Lacertae ◽  
High Energy Gamma ◽  
Large Numbers ◽  
Wide Range ◽  
Energy Gamma ◽  
Time Variations

AbstractDuring the period from 1992 May to early 1992 November, the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory obtained high-energy gamma-ray data for most of the sky. A total of 18 active galaxies have been seen with high certainty, and it is expected that more will be found in the data when a more thorough analysis is complete. All of those that have been seen are radio-loud quasars or BL Lacertae objects; most have already been identified as blazars. No Seyfert galaxies have been found thus far. If the spectra are represented as a power law in energy, spectral slopes ranging from approximately −1.7 to −2.4 are found. A wide range of z-values exists in the observed sample, eight having values in excess of 1.0. Time variations have been seen, with the timescale for a significant change being as short as days in at least one case. These results imply the existence of very large numbers of relativistic particles, probably close to the central object. Although a large extrapolation is required, their existence also suggests that these active galactic nuclei may be the source of the extragalactic cosmic rays.Subject headings: acceleration of particles — galaxies: active — gamma rays: observations — quasars: general

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