scholarly journals Gamma-Ray Pulsar Emission Models

1996 ◽  
Vol 160 ◽  
pp. 315-322 ◽  
Author(s):  
Alice K. Harding
Keyword(s):  
Spectral Index ◽  
Gamma Ray ◽  
High Energy ◽  
Pulsar Emission ◽  
High Energy Radiation ◽  
X Ray ◽  
Gamma Ray Detectors ◽  
Emerging Patterns ◽  
Increased Sensitivity ◽  
Emission Models

AbstractWith the increased sensitivity of gamma-ray detectors on the Compton Gamma-Ray Observatory (CGRO) the number of presently known gamma-ray pulsars has grown. The new detections are beginning to provide clues to the origin of the high-energy radiation in the form of emerging patterns and correlations among observed quantities such as gamma-ray efficiency and spectral index vs. age. But there are still many questions about the location of the emission and its relation to the radio, optical and X-ray pulses. This paper will review models for gamma-ray emission from pulsars and will examine how well the detailed predictions of these models account for the existing observations.

CdTe and CdZnTe Room-Temperature X-Ray and Gamma Ray Detectors and Imaging Systems

1997 ◽  
Vol 487 ◽  
Author(s):  
Y. Eisen ◽  
A. Shor
Keyword(s):  
Room Temperature ◽  
Gamma Ray ◽  
Hole Mobility ◽  
High Energy ◽  
Medical Diagnostics ◽  
Industrial Applications ◽  
Imaging Systems ◽  
Single Element ◽  
X Ray ◽  
Gamma Ray Detectors

AbstractCdTe and CdZnTe X-ray and gamma ray detectors in the form of single elements or as monolithic segmented arrays have been shown to be useful in imaging systems utilized in medical, research or industrial applications. These detectors possess inherently better energy resolution than scintillators coupled to either photodiodes or photomultipliers, and they may lead to compact imaging systems or to imaging systems of enhanced spatial resolution and better contrast resolution. Photopeak efficiencies of these detectors is greatly affected by relatively low hole mobility-lifetime product and therefore continuing efforts are still underway to improve the characteristics of both CdTe and CdZnTe materials in order to achieve reproducible detectors with higher photopeak efficiencies for either low or high energy gamma rays.The following paper is divided into three parts: The first part compares the characteristics of planar CdTe and CdZnTe single elements nuclear detectors containing metal contacts. Characteristics include: Charge collection efficiencies for both electrons and holes indicated by the mobility-lifetime product, energy resolutions, leakage currents and robustness in field use. The second part describes excellent spectroscopic results using a lcm thick CdZnTe monolithic segmented pad detector array. This part also compares spectra for various gamma energies obtained by this segmented detector to that of a 1 cm 3 detector acting as a single element planar detector. The third part discusses the characteristics of a new generation nuclear gamma camera for medical diagnostics based on room-temperature CdTe and CdZnTe spectrometers and its advantages over an Anger type scintillating nuclear camera.

scholarly journals Modelling X-ray and Gamma-ray Emission from Pulsars

2003 ◽  
Vol 214 ◽  
pp. 177-180
Author(s):  
B. Rudak ◽  
J. Dyks
Keyword(s):  
Space Charge ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Spectra ◽  
Polar Cap ◽  
Unique Case ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Γ Ray

Lightcurves and broadband energy spectra of the brightest X/γ-ray sources among the rotation powered pulsars exhibit unexpected richness of features, making each object almost a unique case. This contribution presents how our models of high-energy radiation within the framework of SCLF (space charge limited flow) polar-cap scenarios tackle with some of these challenges.

scholarly journals EXPECTED GAMMA-RAY EMISSION FROM X-RAY BINARIES

2012 ◽  
Vol 08 ◽  
pp. 43-54
Author(s):  
WŁODEK BEDNAREK
Keyword(s):  
Binary Systems ◽  
Gamma Ray ◽  
High Energy ◽  
Acceleration Process ◽  
High Energy Radiation ◽  
X Ray ◽  
Massive Binary Systems ◽  
Γ Rays ◽  
Radiation Processes ◽  
X Ray Binaries

It is at present well known that conditions at some massive binary systems allow acceleration of particles and production of the GeV-TeV γ-rays. However, which particles are responsible for this emission and what radiation processes are engaged is at present not completely clear. We discuss what parameters can determine the acceleration process of particles and high energy radiation produced by them within massive binary systems.

High-energy radiation visualizer (HERV): a new system for imaging in X-ray and gamma-ray emission regions

1996 ◽  
Vol 43 (4) ◽  
pp. 2427-2433 ◽  
Author(s):  
A.N. Sudarkin ◽  
O.P. Ivanov ◽  
V.E. Stepanov ◽  
A.G. Volkovich ◽  
A.S. Turin ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Gamma Ray Emission ◽  
New System

scholarly journals Pulsar Emission Physics: The First Fifty Years

2017 ◽  
Vol 13 (S337) ◽  
pp. 52-57 ◽  
Author(s):  
Alice K. Harding
Keyword(s):  
Particle Acceleration ◽  
High Energy ◽  
Pulsar Emission ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
High Energies ◽  
Polar Caps ◽  
History Of ◽  
Emission Models ◽  
High Energy Emission

AbstractOver the last fifty years since the discovery of pulsars, our understanding of where and how pulsars emit the radiation we observe has undergone significant revision. The location and mechanisms of high-energy radiation are intimately tied to the sites of particle acceleration. The evolution of emission models has paralleled the development of increasingly more sensitive telescopes, especially at high energies. I will review the history of pulsar emission modeling, from the early days of gaps at the polar caps, to outer gaps and slot gaps in the outer magnetosphere, to the present era of global magnetosphere simulations that locate most acceleration and high-energy emission in the current sheets.

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 The connection between the 15 GHz radio and gamma-ray emission in blazars

2014 ◽  
Vol 10 (S313) ◽  
pp. 17-20
Author(s):  
W. Max-Moerbeck ◽  
J. L. Richards ◽  
T. Hovatta ◽  
V. Pavlidou ◽  
T. J. Pearson ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Statistical Tests ◽  
High Energy ◽  
Light Curves ◽  
Owens Valley ◽  
Noise Characteristics ◽  
Power Spectral ◽  
Emission Models ◽  
Gamma Ray Emission ◽  
Many Sources

AbstractSince mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope (OVRO 40m). One of the main goals of this programme is to study the relation between the radio and gamma-ray emission in blazars and to use it as a tool to locate the site of high energy emission. Using this large sample of objects we are able to characterize the radio variability, and study the significance of correlations between the radio and gamma-ray bands. We find that the radio variability of many sources can be described using a simple power law power spectral density, and that when taking into account the red-noise characteristics of the light curves, cases with significant correlation are rare. We note that while significant correlations are found in few individual objects, radio variations are most often delayed with respect to the gamma-ray variations. This suggests that the gamma-ray emission originates upstream of the radio emission. Because strong flares in most known gamma-ray-loud blazars are infrequent, longer light curves are required to settle the issue of the strength of radio-gamma cross-correlations and establish confidently possible delays between the two. For this reason continuous multiwavelength monitoring over a longer time period is essential for statistical tests of jet emission models.

scholarly journals Fermi-LAT and WMAP observations of the supernova remnant Puppis A

2013 ◽  
Vol 9 (S296) ◽  
pp. 295-299
Author(s):  
Marie-Hélène Grondin ◽  
John W. Hewitt ◽  
Marianne Lemoine-Goumard ◽  
Thierry Reposeur ◽  
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
Gamma Ray ◽  
High Energy ◽  
Radio Spectrum ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Large Area ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Γ Ray

AbstractThe supernova remnant (SNR) Puppis A (aka G260.4-3.4) is a middle-aged supernova remnant, which displays increasing X-ray surface brightness from West to East corresponding to an increasing density of the ambient interstellar medium at the Eastern and Northern shell. The dense IR photon field and the high ambient density around the remnant make it an ideal case to study in γ-rays. Gamma-ray studies based on three years of observations with the Large Area Telescope (LAT) aboard Fermi have revealed the high energy gamma-ray emission from SNR Puppis A. The γ-ray emission from the remnant is spatially extended, and nicely matches the radio and X-ray morphologies. Its γ-ray spectrum is well described by a simple power law with an index of ~2.1, and it is among the faintest supernova remnants yet detected at GeV energies. To constrain the relativistic electron population, seven years of Wilkinson Microwave Anisotropy Probe (WMAP) data were also analyzed, and enabled to extend the radio spectrum up to 93 GHz. The results obtained in the radio and γ-ray domains are described in detail, as well as the possible origins of the high energy γ-ray emission (Bremsstrahlung, Inverse Compton scattering by electrons or decay of neutral pions produced by proton interactions).

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