scholarly journals Escape of TeV Gamma Rays from Anisotropic Thermal Photon Fields in Active Galactic Nuclei

1997 ◽  
Vol 475 (2) ◽  
pp. 534-544 ◽  
Author(s):  
L. Zhang ◽  
K. S. Cheng
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Galactic Nuclei ◽  
Thermal Photon ◽  
Tev Gamma Rays

scholarly journals TeV Gamma Rays from Ultrahigh Energy Cosmic Ray Interactions in the Cores of Active Galactic Nuclei: Lessons from Centaurus A

2010 ◽  
Vol 27 (4) ◽  
pp. 482-489 ◽  
Author(s):  
M. Kachelrieß ◽  
S. Ostapchenko ◽  
R. Tomàs
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Galactic Nuclei ◽  
Cosmic Ray ◽  
Far Infrared ◽  
High Energy ◽  
Ultrahigh Energy ◽  
Very High Energy ◽  
Tev Gamma Rays ◽  
Centaurus A

AbstractTeV gamma rays have been observed from blazars as well as from radio galaxies like M 87 and Centaurus A. In leptonic models, gamma rays above the pair production threshold can escape from the ultrarelativistic jet, because large Lorentz factors reduce the background photon densities compared to those required for isotropic emission. Here we discuss an alternative scenario, where very high energy photons are generated as secondaries from ultrahigh energy cosmic rays interactions in the cores of active galactic nuclei. We show that TeV gamma-rays can escape from the core despite large infrared and ultraviolet backgrounds. For the special case of Centaurus A, we study whether the various existing observations from the far infrared to the ultrahigh energy range can be reconciled within this picture.

scholarly journals PHYSICS INSIGHTS FROM RECENT MAGIC AGN OBSERVATIONS

2009 ◽  
Vol 18 (10) ◽  
pp. 1489-1492
Author(s):  
◽  
ROBERT WAGNER
Keyword(s):  
Energy Spectrum ◽  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
New Physics ◽  
Spectrum Radio ◽  
Tev Gamma Rays ◽  
Radio Quasar

The total set of the 14 active galactic nuclei detected by MAGIC so far includes well-studied bright blazars like Mkn 501, the giant radio galaxy M 87, but also the distant flat-spectrum radio quasar 3C 279, and an intriguing gamma-ray source in the 3C 66A/B region, whose energy spectrum is not compatible with the expectations from 3C 66A. Besides scheduled observations, so far MAGIC succeeded in discovering TeV gamma rays from three blazars following triggers from high optical states. I report selected highlights from recent MAGIC observations of extragalactic TeV gamma-ray sources, emphasizing and discussing the new physics insights the MAGIC observations were able to contribute.

scholarly journals NONTHERMAL EMISSIONS FROM SHOCKED SHELLS DRIVEN BY POWERFUL AGN JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 893-899
Author(s):  
HIROTAKA ITO ◽  
MOTOKI KINO ◽  
NOZOMU KAWAKATU ◽  
SHOICHI YAMADA
Keyword(s):  
Synchrotron Radiation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Cherenkov Telescopes ◽  
Inverse Compton ◽  
Radiative Output ◽  
Radiation Processes ◽  
Tev Gamma Rays ◽  
Nonthermal Emissions ◽  
Compact Sources

We explore the emissions by accelerated electrons in shocked shells driven by jets in active galactic nuclei (AGNs). Focusing on powerful sources which host luminous quasars, the synchrotron radiation and inverse-Compton (IC) scattering of various photons that are mainly produced in the core are considered as radiation processes. We show that the radiative output is dominated by the IC emission for compact sources (≲ 30 kpc), whereas the synchrotron radiation is more important for larger sources. It is predicted that, for powerful sources (L j ~ 1047 ergs s -1), GeV – TeV gamma-rays produced via the IC emissions can be detected by the Fermi satellite and modern Cherenkov telescopes such as MAGIC, HESS and VERITAS if the source is compact.

scholarly journals ACTIVE GALACTIC NUCLEI AND GAMMA RAYS

2012 ◽  
Author(s):  
BERRIE GIEBELS ◽  
FELIX AHARONIAN ◽  
HÉLÈNE SOL
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Galactic Nuclei

scholarly journals Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shigeo S. Kimura ◽  
Kohta Murase ◽  
Péter Mészáros
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Hadronic Interactions ◽  
Neutrino Detectors ◽  
Accretion Flows ◽  
Diffuse Background ◽  
The Universe

AbstractThe Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously. Low-luminosity active galactic nuclei have hot accretion flows where thermal electrons naturally emit soft gamma rays via Comptonization of their synchrotron photons. Protons there can be accelerated via turbulence or reconnection, producing high-energy neutrinos via hadronic interactions. We demonstrate that our model can reproduce the gamma-ray and neutrino data. Combined with a contribution by hot coronae in luminous active galactic nuclei, these accretion flows can explain the keV – MeV photon and TeV – PeV neutrino backgrounds. This scenario can account for the MeV background without non-thermal electrons, suggesting a higher transition energy from the thermal to nonthermal Universe than expected. Our model is consistent with X-ray data of nearby objects, and testable by future MeV gamma-ray and high-energy neutrino detectors.

A Search for Ultrahigh-Energy Gamma Rays from EGRET-detected Active Galactic Nuclei Using CASA-MIA

1996 ◽  
Vol 469 ◽  
pp. 572 ◽  
Author(s):  
M. Catanese ◽  
A. Borione ◽  
C. E. Covault ◽  
J. W. Cronin ◽  
B. E. Fick ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Galactic Nuclei ◽  
Ultrahigh Energy ◽  
Energy Gamma

scholarly journals Hot Accretion Disks and the High Energy Background

1983 ◽  
Vol 104 ◽  
pp. 345-346
Author(s):  
M. Kafatos ◽  
Jean A. Eilek
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Spectral Range ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
High Energy ◽  
X Rays ◽  
X Ray

The origin of the high energy (X-ray and gamma-ray) background may be attributed to discrete sources, which are usually thought to be active galactic nuclei (AGN) (cf. Rothschild et al. 1982, Bignami et al. 1979). At X-rays a lot of information has been obtained with HEAO-1 in the spectral range 2–165 keV. At gamma-rays the background has been estimated from the Apollo 15 and 16 (Trombka et al. 1977) and SAS-2 (Bignami et al. 1979) observations. A summary of some of the observations (Rothschild et al. 1982) is shown in Figure 1. The contribution of AGN to the diffuse high energy background is uncertain at X-rays although it is generally estimated to be in the 20–30% range (Rothschild et al. 1982). At gamma-rays, in the range 1–150 MeV, AGN (specifically Seyfert galaxies) could account for all the emission.

Sign in / Sign up

Export Citation Format

Share Document