scholarly journals Particle Acceleration in High-Energy Gamma-Ray Sources

1994 ◽  
Vol 142 ◽  
pp. 877-881
Author(s):  
David Eichler
Keyword(s):  
Gamma Rays ◽  
Production Efficiency ◽  
Gamma Ray ◽  
High Energy ◽  
Thick Target ◽  
Shock Acceleration ◽  
High Production Efficiency ◽  
Energy Gamma ◽  
High Production ◽  
High Energy Particles

AbstractMany proficient gamma-ray sources show energy spectra that are consistent with E−2 primary spectra. Such sources include recently identified gamma-ray quasars and some gamma-ray bursts. Assuming thick target conversion, this is consistent with shock acceleration, and the dominance of the gamma rays of the luminosity is also consistent with previous predictions of high production efficiency of fresh cosmic rays in shocks. The spectral cutoffs in the gamma rays may offer clues as to whether the high-energy particles are electrons or protons. Resolution of this matter might have implications for the nature of the sources and for theory of shock accelerated electrons.Subject headings: acceleration of particles — gamma rays: bursts — shock waves

scholarly journals G279.0+1.1: a new extended source of high-energy gamma-rays

2020 ◽  
Vol 492 (4) ◽  
pp. 5980-5986
Author(s):  
M Araya
Keyword(s):  
Spectral Index ◽  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Particle Spectrum ◽  
Large Area ◽  
Extended Source ◽  
The North ◽  
Energy Gamma ◽  
High Energy Emission

ABSTRACT G279.0+1.1 is a supernova remnant (SNR) with poorly known parameters, first detected as a dim radio source and classified as an evolved system. An analysis of data from the Fermi-Large Area Telescope (LAT) revealing for the first time an extended source of gamma-rays in the region is presented. The diameter of the GeV region found is ${\sim} 2{^{\circ}_{.}}8$, larger than the latest estimate of the SNR size from radio data. The gamma-ray emission covers most of the known shell and extends further to the north and east of the bulk of the radio emission. The photon spectrum in the 0.5–500 GeV range can be described by a simple power law, $\frac{\mathrm{ d}N}{\mathrm{ d}E} \propto E^{-\Gamma }$, with a spectral index of Γ = 1.86 ± 0.03stat ± 0.06sys. In the leptonic scenario, a steep particle spectrum is required and a distance lower than the previously estimated value of 3 kpc is favoured. The possibility that the high-energy emission results from electrons that already escaped the SNR is also investigated. A hadronic scenario for the gamma-rays yields a particle spectral index of ∼2.0 and no significant constraints on the distance. The production of gamma-rays in old SNRs is discussed. More observations of this source are encouraged to probe the true extent of the shell and its age.

scholarly journals Very High Energy Gamma Rays from Plerions: CANGAROO Results

1998 ◽  
Vol 188 ◽  
pp. 125-128
Author(s):  
T. Kifune
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Current Status ◽  
Emission Region ◽  
Thermal Processes ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

The current status of very high energy gamma ray astronomy (in ~ 1 TeV region) is described by using as example results of CANGAROO (Collaboration of Australia and Nippon for a GAmma Ray Observatory in the Outback). Gamma rays at TeV energies, emitted through inverse Compton effect of electrons or π0 decay from proton interaction, provide direct evidence on “hot” non-thermal processes of the Universe, as well as environmental features, such as the strength of magnetic field in the emission region, for the non-thermal processes.

scholarly journals Physical Constraints on Models of Gamma-Ray Bursters

1986 ◽  
Vol 89 ◽  
pp. 305-321
Author(s):  
Richard I. Epstein
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
X Rays ◽  
Burst Source ◽  
Gamma Ray Burst ◽  
Physical Constraints ◽  
Low Energies ◽  
Energy Gamma ◽  
Photon Interactions

AbstractThe power per logarithmic bandwidth in gamma-ray burst spectra generally increases rapidly with energy through the x-ray range and does not cut off sharply above a few MeV. This spectral form indicates that a very small fraction of the energy from a gamma-ray burst source is emitted at low energies or is reprocessed into x-rays and that the high-energy gamma rays are not destroyed by photon-photon interactions. The implications are that the emission mechanism for the gamma-ray bursts is not synchrotron radiation from electrons that lose most of their energy before being re-accelerated and that either the regions from which the gamma rays are emitted are large compared to the size of a neutron star or the emission is collimated and beamed away from the stellar surface.

Gamma-Ray Solar Flares and In Situ Particle Acceleration

2017 ◽  
Vol 13 (S335) ◽  
pp. 43-48 ◽  
Author(s):  
Alexei Struminsky
Keyword(s):  
Gamma Ray ◽  
Solar Energetic Particle ◽  
High Energy ◽  
Shock Acceleration ◽  
Relative Role ◽  
Energy Gamma ◽  
Mass Ejection ◽  
Flare Site

AbstractAt present two concurrent paradigms of solar energetic particle (SEP) origin exist: acceleration directly in the flare site or by the shock wave of coronal mass ejection (CME). Active discussions on a relative role of flares and coronal mass ejections for SEP acceleration and propagation are continuous until now. In my opinion only future observations of solar high energy γ–emission with better spectral, spatial and temporal resolution may clarify this issue. In my report I discuss possible signatures of the flare and shock acceleration processes. What is a picture provided by the current instruments? What can we expect to observe with a perfect instrument in high energy gamma rays in one or another case on a time scale of impulsive and long decay flare phases?

A search for high-energy gamma rays (?1015 eV) associated with gamma ray bursts

1982 ◽  
Vol 83 (1-2) ◽  
pp. 279-286 ◽  
Author(s):  
R. W. Clay ◽  
P. R. Gerhardy ◽  
A. G. Gregory
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
High Energy Gamma ◽  
Energy Gamma

scholarly journals Very high energy gamma-rays from flat spectrum radio quasars

2014 ◽  
Vol 10 (S313) ◽  
pp. 27-32
Author(s):  
Elina Lindfors
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Spectrum Radio ◽  
Very High Energy ◽  
Energy Gamma ◽  
Emission Models ◽  
Γ Rays ◽  
Very High

AbstractThe detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100 GeV) range is challenging, mainly because of their steep soft spectra and distance. Nevertheless four FSRQs are now known to be VHE emitters. The detection of the VHE γ-rays has challenged the emission models of these sources. The sources are also found to exhibit very different behavior. I will give an overview of what is known about the VHE emission of these sources and about the multiwavelength signatures that are connected to the VHE gamma-ray emission.

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