EXTRAGALACTIC GAMMA-RAYS: GAMMA RAY BURSTS AND BLAZARS

2005 ◽  
Vol 20 (29) ◽  
pp. 6991-7000 ◽  
Author(s):  
GABRIELE GHISELLINI
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Gamma Ray Bursts ◽  
Relativistic Energy ◽  
Random Energy ◽  
The Universe

The extragalactic gamma-ray sky is dominated by two classes of sources: Gamma-Ray Bursts (GRBs) and radio loud active galactic nuclei whose jets are pointing at us (blazars). We believe that the radiation we receive from them originates from the transformation of bulk relativistic energy into random energy. Although the mechanisms to produce, collimate and accelerate the jets in these sources are uncertain, it is fruitful to compare the characteristics of both classes of sources in search of enlightening similarities. I will review some general characteristics of radio loud AGNs and GRBs and I will discuss the possibility that both classes of sources can work in the same way. Finally, I will discuss some recent exciting prospects to use blazars to put constraints on the cosmic IR-Optical-UV backgrounds, and to use GRBs as standard candles to measure the Universe.

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.

scholarly journals WORMHOLES, GAMMA RAY BURSTS AND THE AMOUNT OF NEGATIVE MASS IN THE UNIVERSE

1998 ◽  
Vol 13 (19) ◽  
pp. 1575-1581 ◽  
Author(s):  
DIEGO F. TORRES ◽  
LUIS A. ANCHORDOQUI ◽  
GUSTAVO E. ROMERO
Keyword(s):  
Active Galactic Nuclei ◽  
Satellite Data ◽  
Upper Bound ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Gamma Ray Bursts ◽  
Negative Mass ◽  
The Universe

In this letter, we assume that negative mass objects can exist in the extragalactic space and analyze the consequences of their microlensing on light from distant active galactic nuclei. We find that such events have very similar features to some observed gamma ray bursts and use recent satellite data to set an upper bound to the amount of negative mass in the universe.

The photometric system of the Nanshan One-meter Wide field Telescope

2013 ◽  
Vol 9 (S298) ◽  
pp. 427-427
Author(s):  
Jinzhong Liu ◽  
Yu Zhang ◽  
Guojie Feng ◽  
Chunhai Bai
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Variable Stars ◽  
Optical Quality ◽  
Gamma Ray Bursts ◽  
Wide Field ◽  
Photometric System ◽  
Tracking Accuracy ◽  
Pointing Accuracy

AbstractA one-meter wide field astronomical telescope with Alt-Az mount, putting in work at prime focus with field corrector, is located at the Nanshan site of Xinjiang Astronomical Observatory. The Nanshan One meter Wide-field Telescope (hereafter NOWT) provides excellent optical quality, pointing accuracy and tracking accuracy. The main scientific goals of NOWT are supernovae, gamma-ray bursts, novae, variable stars, and active galactic nuclei. It is worthwhile to point out that the sky background at the Nanshan is a classic optical site.

scholarly journals Looking for the possible gluon condensation signature in sub-TeV gamma-ray spectra: from active galactic nuclei to gamma ray bursts

2021 ◽  
Vol 2021 (01) ◽  
pp. 038-038
Author(s):  
Wei Zhu ◽  
Zechun Zheng ◽  
Peng Liu ◽  
Lihong Wan ◽  
Jianhong Ruan ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Gamma Ray Bursts

Chapter 3 Extra-galactic Gamma-Ray Sources

2021 ◽  
Author(s):  
Xiang-Yu Wang
Keyword(s):  
Active Galactic Nuclei ◽  
Lower Energy ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Starburst Galaxies ◽  
Gamma Ray Bursts ◽  
Cherenkov Detector ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Water Cherenkov Detector

Abstract Extra-galactic gamma-ray sources, such as gamma-ray bursts, active galactic nuclei, starburst galaxies, are interesting and important targets for LHAASO observations. In this chapter, the prospects of detecting these sources with LHAASO and their physical implications are studied. The upgrade plan for the Water Cherenkov Detector Array (WCDA), which aims to enhance the detectability of relatively lower energy photons, is also presented. In addition, a study on constraining the extragalactic background light with LHAASO observation of blazars is presented.

scholarly journals RADIATION MECHANISM AND JET COMPOSITION OF GAMMA-RAY BURSTS AND GeV-TeV-SELECTED RADIO-LOUD ACTIVE GALACTIC NUCLEI

2013 ◽  
Vol 774 (1) ◽  
pp. L5 ◽  
Author(s):  
Jin Zhang ◽  
En-Wei Liang ◽  
Xiao-Na Sun ◽  
Bing Zhang ◽  
Ye Lu ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Gamma Ray Bursts ◽  
Radiation Mechanism

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.

LIMITS TO THE PHYSICAL PARAMETERS IN EXTRAGALACTIC GAMMA-RAY SOURCES

2009 ◽  
Vol 18 (10) ◽  
pp. 1523-1527 ◽  
Author(s):  
E. V. DERISHEV
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Physical Parameters ◽  
Gamma Ray Burst ◽  
Upper Limits

We examine several constraints on the physical parameters in active galactic nuclei and gamma-ray burst, originating from the assumption that these sources are efficient in converting their energy into gamma-rays. It is shown that in most cases these constraints may be reformulated in terms of bounds on the jet Lorentz factor, for which both the lower and the upper limits can be evaluated.

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