Future prospects for y-ray astronomy

1981 ◽  
Vol 301 (1462) ◽  
pp. 693-701 ◽  
Keyword(s):  
Gamma Ray ◽  
Dynamic Pressure ◽  
High Energy ◽  
Compact Objects ◽  
Pressure Effects ◽  
Very High Energy ◽  
Order Of Magnitude ◽  
High Energy Particles ◽  
Nuclear Processes ◽  
The Universe

As y-ray astronomy moves from the discovery to the exploratory phase, the promise of y-ray astrophysics noted by theorists in the late 1940s and 1950s is beginning to be realized. In the future, satellites should carry instruments that will have over an order of magnitude greater sensitivity than those flown thus far, and, for at least some portions of the y-ray energy range, these detectors will also have substantially improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance our knowledge of several astrophysical phenomena including the very energetic and nuclear processes associated with compact objects, astrophysical nucleosynthesis, solar particle acceleration, the chemical composition of the planets and other bodies of the Solar System, the structure of our Galaxy, the origin and dynamic pressure effects of the cosmic rays, high energy particles and energetic processes in other galaxies especially active ones, and the degree of matter-antimatter symmetry of the Universe. The y-ray results of the forthcoming programs such as Gamma-I, the Gamma Ray Observatory, the y-ray burst network, Solar Polar, and very high energy y-ray telescopes on the ground will almost certainly provide justification for more sophisticated telescopes. These advanced instruments might be placed on the Space Platform currently under study by N.A.S.A.

scholarly journals The Galactic Center Region Imaged by VERITAS from 2010{2012

2014 ◽  
Vol 1 (1) ◽  
pp. 227-230
Author(s):  
Matthias Beilicke
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Galactic Center ◽  
Region Of Interest ◽  
High Energy ◽  
Central Black Hole ◽  
Potential Sources ◽  
Very High Energy ◽  
Order Of Magnitude ◽  
Very High

The galactic center has long been a region of interest for high-energy and very-high-energy observations. Many potential sources of GeV/TeV gamma-ray emission are located in this region, e.g. the accretion of matter onto the central black hole, cosmic rays from a nearby shell-type supernova remnant, or the annihilation of dark matter. The galactic center has been detected at MeV/GeV energies by EGRET and recently by <em>Fermi</em>/LAT. At TeV energies, the galactic center was detected at the level of 4 standard deviations with the Whipple 10m telescope and with one order of magnitude better sensitivity by H.E.S.S. and MAGIC. We present the results from 3 years of VERITAS galactic center observations conducted at large zenith angles. The results are compared to astrophysical models.

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 Radiation GRMHD simulations of M87: Funnel properties and prospects for gap acceleration

2021 ◽  
Author(s):  
Philippe Z Yao ◽  
Jason Dexter ◽  
Alexander Y Chen ◽  
Benjamin R Ryan ◽  
George N Wong
Keyword(s):  
Black Hole ◽  
Radiation Field ◽  
Gamma Ray ◽  
Theoretical Models ◽  
High Energy ◽  
Point Sources ◽  
Photon Momentum ◽  
Very High Energy ◽  
Order Of Magnitude ◽  
General Relativistic

Abstract We use the public code ebhlight to carry out 3D radiative general relativistic magnetohydrodynamics (GRMHD) simulations of accretion on to the supermassive black hole in M87. The simulations self-consistently evolve a frequency-dependent Monte Carlo description of the radiation field produced by the accretion flow. We explore two limits of accumulated magnetic flux at the black hole (SANE and MAD), each coupled to several sub-grid prescriptions for electron heating that are motivated by models of turbulence and magnetic reconnection. We present convergence studies for the radiation field and study its properties. We find that the near-horizon photon energy density is an order of magnitude higher than is predicted by simple isotropic estimates from the observed luminosity. The radially dependent photon momentum distribution is anisotropic and can be modeled by a set of point-sources near the equatorial plane. We draw properties of the radiation and magnetic field from the simulation and feed them into an analytic model of gap acceleration to estimate the very high energy (VHE) gamma-ray luminosity from the magnetized jet funnel, assuming that a gap is able to form. We find luminosities of $\rm \sim 10^{41} \, erg \, s^{-1}$ for MAD models and $\rm \sim 2\times 10^{40} \, erg \, s^{-1}$ for SANE models, which are comparable to measurements of M87’s VHE flares. The time-dependence seen in our calculations is insufficient to explain the flaring behaviour. Our results provide a step towards bridging theoretical models of near-horizon properties seen in black hole images with the VHE activity of M87.

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.

Perspectives from CTA in relativistic astrophysics

2017 ◽  
Vol 26 (03) ◽  
pp. 1730005
Author(s):  
Werner Hofmann
Keyword(s):  
Gamma Ray ◽  
Extreme Environments ◽  
High Energy ◽  
Superior Performance ◽  
Relativistic Astrophysics ◽  
Wide Field ◽  
Star Forming ◽  
Cherenkov Telescopes ◽  
Very High Energy ◽  
Order Of Magnitude

The Cherenkov telescope array (CTA) is a next-generation observatory for very high energy (VHE) gamma-ray astronomy. With one array of imaging atmospheric Cherenkov telescopes each in the Northern and Southern Hemispheres, CTA will provide full-sky coverage, enhance flux sensitivity by one order of magnitude compared to current instruments, cover gamma-ray energies from 20 GeV to 300 GeV, and provide a wide field of view with angular resolution of a few arc-minutes. Science themes to be addressed by the CTA observatory include (i) understanding the origin of relativistic cosmic particles, and the role these play in the evolution of star forming systems and galaxies, (ii) probing extreme environments such as neutron stars and black holes, but also the cosmic voids, and (iii) exploring frontiers in physics such as the nature of dark matter. With its superior performance, the prospects for CTA combine guaranteed science — the in-depth understanding of known objects and mechanisms — with anticipated detection of new classes of gamma-ray emitters and new phenomena, and a very significant potential for fundamentally new discoveries.

scholarly journals Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 36
Author(s):  
Yoshiyuki Inoue ◽  
Dmitry Khangulyan ◽  
Akihiro Doi
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Thermal Activity ◽  
X Ray ◽  
Cascade Models ◽  
Coronal Activity ◽  
Ngc 1068 ◽  
High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

scholarly journals Modeling Gamma-Ray SEDs and Angular Extensions of Extreme TeV Blazars from Intergalactic Proton-Initiated Cascades in Contemporary Astrophysical EGMF Models

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 220
Author(s):  
Emil Khalikov
Keyword(s):  
Gamma Rays ◽  
Large Scale ◽  
Gamma Ray ◽  
High Energy ◽  
Cascade Model ◽  
Point Sources ◽  
Spectral Energy ◽  
Observation Data ◽  
Cherenkov Telescopes ◽  
The Universe

The intrinsic spectra of some distant blazars known as “extreme TeV blazars” have shown a hint at an anomalous hardening in the TeV energy region. Several extragalactic propagation models have been proposed to explain this possible excess transparency of the Universe to gamma-rays starting from a model which assumes the existence of so-called axion-like particles (ALPs) and the new process of gamma-ALP oscillations. Alternative models suppose that some of the observable gamma-rays are produced in the intergalactic cascades. This work focuses on investigating the spectral and angular features of one of the cascade models, the Intergalactic Hadronic Cascade Model (IHCM) in the contemporary astrophysical models of Extragalactic Magnetic Field (EGMF). For IHCM, EGMF largely determines the deflection of primary cosmic rays and electrons of intergalactic cascades and, thus, is of vital importance. Contemporary Hackstein models are considered in this paper and compared to the model of Dolag. The models assumed are based on simulations of the local part of large-scale structure of the Universe and differ in the assumptions for the seed field. This work provides spectral energy distributions (SEDs) and angular extensions of two extreme TeV blazars, 1ES 0229+200 and 1ES 0414+009. It is demonstrated that observable SEDs inside a typical point spread function of imaging atmospheric Cherenkov telescopes (IACTs) for IHCM would exhibit a characteristic high-energy attenuation compared to the ones obtained in hadronic models that do not consider EGMF, which makes it possible to distinguish among these models. At the same time, the spectra for IHCM models would have longer high energy tails than some available spectra for the ALP models and the universal spectra for the Electromagnetic Cascade Model (ECM). The analysis of the IHCM observable angular extensions shows that the sources would likely be identified by most IACTs not as point sources but rather as extended ones. These spectra could later be compared with future observation data of such instruments as Cherenkov Telescope Array (CTA) and LHAASO.

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