Constraints on the Very High Energy Emissivity of the Universe from the Diffuse G[CLC]e[/CLC]V Gamma-Ray Background

1997 ◽  
Vol 487 (1) ◽  
pp. L9-L12 ◽  
Author(s):  
Paolo S. Coppi ◽  
Felix A. Aharonian
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Very High Energy ◽  
The Universe ◽  
Very High

scholarly journals Search for High Energy emission from GRBs with MAGIC

2016 ◽  
Vol 12 (S324) ◽  
pp. 70-73
Author(s):  
Alessio Berti ◽  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Cherenkov Telescopes ◽  
Gamma Ray Imaging ◽  
Very High Energy ◽  
Γ Rays ◽  
High Energy Emission ◽  
The Universe ◽  
Very High

AbstractGamma-Ray Bursts (GRBs) are the most violent explosions in the Universe, releasing a huge amount of energy in few seconds. While our understanding of the prompt and the afterglow phases has increased with Swift and Fermi, we have very few information about their High Energy (HE, E ≲ 100) emission components. This requires a ground-based experiment able to perform fast follow-up with enough sensitivity above ~ 50 GeV. The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes have been designed to perform fast follow-up on GRBs thanks to fast slewing movement and low energy threshold (~ 50 GeV). Since the beginning of the operations, MAGIC followed-up 89 GRBs in good observational conditions. In this contribution the MAGIC GRBs follow-up campaign and the results which could be obtained by detecting HE and Very High Energy (VHE, E ≳ 100 GeV) γ-rays from GRBs will be reviewed.

scholarly journals The Prospects for Very High Energy Gamma Ray Astronomy

1995 ◽  
Vol 48 (2) ◽  
pp. 305 ◽  
Author(s):  
T Kifune
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Coming Of Age ◽  
High Energy ◽  
Detection Techniques ◽  
Gamma Ray Astronomy ◽  
Very High Energy ◽  
Energy Gamma ◽  
The Universe ◽  
Very High

Very-high-energy (VHE) gamma rays, with energies .<: 1 TeV = 1012 eV, are observed with ground-based telescopes using the atmospheric Cerenkov technique. This field of astronomy has recently experienced its coming of age, opening a new observational window on the universe after efforts spanning almost 30 years. Recent advances in this field have been aided by the results from satellite detectors with high-energy (HE) gamma ray 'eyes'. Satellite detectors are sensitive to HE gamma rays, up to energies of about 10 GeV = 1010 eV. In this paper, VHE gamma ray astronomy is reviewed, and the 3�8 m diameter telescope of the Japanese-Australian CANGAROO project is used to illustrate the detection techniques. As VHE gamma ray astronomy is closely related to observations in the HE region, results from recent satellite experiments are also discussed.

scholarly journals Effect of axion-like particles on the spectrum of the extragalactic gamma-ray background

2021 ◽  
Vol 2021 (11) ◽  
pp. 030
Author(s):  
Yun-Feng Liang ◽  
Xing-Fu Zhang ◽  
Ji-Gui Cheng ◽  
Hou-Dun Zeng ◽  
Yi-Zhong Fan ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Small Region ◽  
High Energy ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Very High Energy ◽  
The Universe ◽  
Very High

Abstract Axion-like particles (ALPs) provide a feasible explanation for the observed lower TeV opacity of the Universe. If the anomaly TeV transparency is caused by ALPs, then the fluxes of distant extragalactic sources will be enhanced at photon energies beyond TeV, resulting in an enhancement of the observed extragalactic gamma-ray background (EGB) spectrum. In this work, we have investigated the ALP modulation on the EGB spectrum at TeV energies. Our results show that in the most optimistic case, the existence of ALPs can cause the EGB spectrum to greatly deviate from the prediction of a pure extragalactic-background-light (EBL) absorption scenario. The deviation occurs at approximately ≳1 TeV, and the current EGB measurements by Fermi-LAT cannot identify such an effect. We also find that most of the sensitive ALP parameters have been ruled out by existing constraints, leaving only a small region of unrestricted parameters that can be probed using the EGB effect investigated in this work. Observations from forthcoming very-high-energy instruments like LHAASO and CTA may be beneficial for the study of this effect.

scholarly journals A STRONG RADIO BRIGHTENING AT THE JET BASE OF M 87 DURING THE ELEVATED VERY HIGH ENERGY GAMMA-RAY STATE IN 2012

2014 ◽  
Vol 788 (2) ◽  
pp. 165 ◽  
Author(s):  
K. Hada ◽  
M. Giroletti ◽  
M. Kino ◽  
G. Giovannini ◽  
F. D'Ammando ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

scholarly journals Future science issues for Galactic very-high-energy gamma-ray astronomy

2008 ◽  
Author(s):  
Diego F. Torres ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
Frank Rieger
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Astronomy ◽  
High Energy Gamma ◽  
Future Science ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

BINARY PULSAR SYSTEM PSR B1259-63/LS2883 AS A GAMMA-RAY EMITTER

2014 ◽  
Vol 28 ◽  
pp. 1460169 ◽  
Author(s):  
DMITRY KHANGULYAN ◽  
SERGEY V. BOGOVALOV ◽  
FELIX A. AHARONIAN
Keyword(s):  
Energy Band ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Losses ◽  
Binary Pulsar ◽  
Emission Component ◽  
Emission Enhancement ◽  
Very High Energy ◽  
Hydrodynamical Simulations ◽  
Very High

Observations of the binary pulsar PSR B1259-63/LS2883 in the high energy and very high energy domains have revealed a few quite unusual features. One of the most puzzling phenomena is the bright GeV flare detected with Fermi/LAT in 2011 January, approximately one month after periastron passage. Since the maximum luminosity in the high energy band during the flare nearly achieved the level of the pulsar spin-down energy losses, it is likely that the particles, responsible for this emission component, had a strongly anisotropic distribution, which resulted in the emission enhancement. One of the most prolific scenarios for such an emission enhancement is the Doppler boosting, which is realized in sources with relativistic motions. Interestingly, a number of hydrodynamical simulations have predicted a formation of highly relativistic outflows in binary pulsar systems, therefore scenarios, involving relativistic boosting, are very natural for these systems. However a more detailed analysis of such a possibility, presented in this study, reveals certain limitations which put strict constraints on the maximum luminosity achievable in this scenario. These constraints render the "Doppler boosting" scenario to be less feasible, especially for the synchrotron models.

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