scholarly journals The role of the diffusive protons in the gamma-ray emission of SNR RX J1713.7-3946

2017 ◽  
Vol 12 (S331) ◽  
pp. 304-309
Author(s):  
Xiao Zhang ◽  
Yang Chen
Keyword(s):  
Shock Wave ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Broad Band ◽  
High Energy ◽  
Band Spectrum ◽  
Zone Model ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Particles

AbstractRX J1713.7-3946 is a prototype in the γ-ray-bright supernova remnants (SNRs) and is in continuing debates on its hadronic versus leptonic origin of the γ-ray emission. We explore the role played by the diffusive relativistic protons that escape from the SNR shock wave in the γ-ray emission, apart from the emission of high energy particles from the inside of the SNR. In the scenario that the SNR shock propagates in a clumpy molecular cavity, we consider that the γ-ray emission from the inside of the SNR may either arise from the IC scattering or from the interaction between the trapped energetic protons and the shocked clumps. The dominant origin between them depends on the electron-to-proton number ratio. The surrounding molecular cavity wall is considered to also produce γ-ray emission due to the “illumination” by the diffusive protons that escaped from the shock wave during the expansion history. The broad-band spectrum can be well explained by this two-zone model, in which the γ-ray emission from the inside governs the TeV band, while the outer emission component substantially contributes to the GeV γ-rays. The two-zone model can also explain the TeV γ-ray radial brightness profile that significantly stretches beyond the nonthermal X-ray emitting region.

scholarly journals Molecular Clouds Observed by the EGRET Gamma-Ray Telescope

1997 ◽  
Vol 170 ◽  
pp. 22-24 ◽  
Author(s):  
Seth. W. Digel ◽  
Stanley D. Hunter ◽  
Reshmi Mukherjee ◽  
Eugéne J. de Geus ◽  
Isabelle A. Grenier ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Molecular Clouds ◽  
Gamma Ray ◽  
Angular Resolution ◽  
Cosmic Ray ◽  
High Energy ◽  
Background Rejection ◽  
Γ Rays ◽  
Γ Ray ◽  
Production Mechanisms

EGRET, the high-energy γ-ray telescope on the Compton Gamma-Ray Observatory, has the sensitivity, angular resolution, and background rejection necessary to study diffuse γ-ray emission from the interstellar medium (ISM). High-energy γ rays produced in cosmic-ray (CR) interactions in the ISM can be used to determine the CR density and calibrate the CO line as a tracer of molecular mass. Dominant production mechanisms for γ rays of energies ∼30 MeV–30 GeV are the decay of pions produced in collisions of CR protons with ambient matter and Bremsstrahlung scattering of CR electrons.

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).

scholarly journals A Possible Discovery of a Flaring 1012 eV Gamma-Ray Source near the Red Dwarf EV Lac

1995 ◽  
Vol 151 ◽  
pp. 78-79
Author(s):  
I.Yu. Alekseev ◽  
N.N. Chalenko ◽  
V.P. Fomin ◽  
R.E. Gershberg ◽  
O.R. Kalekin ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Electronic Device ◽  
Angular Size ◽  
High Energy ◽  
Optical Systems ◽  
Relativistic Electrons ◽  
Large Area ◽  
Γ Rays ◽  
Γ Ray ◽  
Ev Lac

During the 1994 coordinated observations of the red dwarf flare star EV Lac, the star was monitored in the very high energy (VHE) γ-ray range around 1012 eV with the Crimean ground-based γ-ray telescope GT-48. This telescope consists of two identical optical systems (Vladimirsky et al. 1994) which were directed in parallel on EV Lac.The detection principle of the VHE γ-rays is based on the Čerenkov radiation emitted by relativistic electrons and positrons. The latter are generated in the interaction of the γ-rays with nuclei in the Earth’s atmosphere that leads to an appearance of a shower of charged particles and γ-quanta. The duration of the Cherenkov radiation flash is very short, just about a few nanoseconds. The angular size of the shower is ∼ 1°. To detect such flashes we use an optical system with large area mirrors and a set of 37 photomultipliers (PMs) in the focal plane. Using the information from these PMs which are spaced hexagonally and correspond to a field of view of 2°.6 on the sky, we can obtain the image of an optical flash. The electronic device permits us to detect nanosecond flashes (40 ns exposure time and 12 μs readout dead-time).

scholarly journals Optical Monitoring of Gamma-Ray Loud Blazars

1996 ◽  
Vol 175 ◽  
pp. 287-288
Author(s):  
C.M. Raiteri ◽  
G. Ghisellini ◽  
M. Villata ◽  
G. DE FRANCESCO ◽  
S. Bosio ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Significant Fraction ◽  
Optical Monitoring ◽  
Inverse Compton ◽  
Theoretical Predictions ◽  
Γ Ray ◽  
Uv Photons ◽  
High Energy Particles ◽  
Crucial Test

The observations by the Compton Gamma Ray Observatory (CGRO) have shown that highly variable and radio-loud quasars emit a significant fraction of their energy in the γ band. According to the Inverse Compton model, the γ-ray emission is due to upscattering of soft (IR-optical-UV) photons by high energy particles. Optical monitoring is thus of great value in providing information on the mechanisms that rule the production of the seed photons for the γ-ray radiation and on the γ-ray emission itself. In particular, detection of variability correlations between optical and γ-ray emissions would be a crucial test for the theoretical predictions.

scholarly journals OBSERVATION OF GALACTIC SOURCES OF VERY HIGH ENERGY γ-RAYS WITH THE MAGIC TELESCOPE

2007 ◽  
Vol 22 (29) ◽  
pp. 2167-2174
Author(s):  
H. BARTKO
Keyword(s):  
Supernova Remnants ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Γ Radiation ◽  
La Palma ◽  
Very High Energy ◽  
Γ Rays ◽  
Galactic Sources ◽  
Very High

The MAGIC telescope with its 17m diameter mirror is today the largest operating single-dish Imaging Air Cherenkov Telescope (IACT). It is located on the Canary Island La Palma, at an altitude of 2200 m above sea level, as part of the Roque de los Muchachos European Northern Observatory. The MAGIC telescope detects celestial very high energy γ-radiation in the energy band between about 50 GeV and 10 TeV. Since the autumn of 2004 MAGIC has been taking data routinely, observing various objects, like supernova remnants (SNRs), γ-ray binaries, Pulsars, Active Galactic Nuclei (AGN) and Gamma-ray Bursts (GRB). We briefly describe the observational strategy, the procedure implemented for the data analysis, and discuss the results of observations of Galactic Sources.

scholarly journals Extreme and high synchrotron peak blazars beyond 4FGL: The 2BIGB γ-ray catalogue

2020 ◽  
Vol 493 (2) ◽  
pp. 2438-2451
Author(s):  
B Arsioli ◽  
Y-L Chang ◽  
B Musiimenta
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Data Repositories ◽  
Total Contribution ◽  
Public Data ◽  
Γ Ray

ABSTRACT This paper presents the results of a γ-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 yr of observations in the energy range between 500 MeV and 500 GeV, which results in 1160 γ-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ∼25 per cent for the number of EHSP and HSP currently described in γ-rays. We build the γ-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding γ-ray logN−logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ∼33 per cent at 100 GeV. Also, we show that the γ-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for ‘Second Brazil-ICRANet Gamma-ray Blazars’ catalogue, and all the broad-band models and SED data points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC).

scholarly journals High-energy emission from galaxies: the star-formation/gamma-ray connection

2011 ◽  
Vol 7 (S284) ◽  
pp. 382-388
Author(s):  
Stefan Ohm ◽  
Jim Hinton
Keyword(s):  
Particle Acceleration ◽  
Star Formation ◽  
Gamma Ray ◽  
Broad Band ◽  
High Energy ◽  
High Mass ◽  
Spectral Energy ◽  
Mass Star ◽  
Γ Ray ◽  
The Impact

AbstractThe impact of non-thermal processes on the spectral energy distributions of galaxies can be dramatic, but such processes are often neglected in considerations of their structure and evolution. Particle acceleration associated with high mass star formation and AGN activity not only leads to very broad band (radio-γ-ray) emission, but may also produce very significant feedback effects on galaxies and their environment. The recent detections of starburst galaxies at GeV and TeV energies suggest that γ-ray instruments have now reached the critical level of sensitivity to probe the connection between particle acceleration and star-formation in galaxies. In this paper we will try to summarise this recent progress, put it into a multi-wavelength context and also discuss the prospects for more precise and sensitive γ-ray measurements with the upcoming CTA observatory.

scholarly journals Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Hiromasa Suzuki ◽  
Aya Bamba ◽  
Ryo Yamazaki ◽  
Yutaka Ohira
Keyword(s):  
Power Law ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Spectral Shape ◽  
X Ray ◽  
Galactic Cosmic Ray ◽  
High Energy Particles ◽  
Accelerated Particles

Abstract In the current decade, GeV/TeV gamma-ray observations of several supernova remnants (SNRs) have implied that accelerated particles are escaping from their acceleration sites. However, when and how they escape from the SNR vicinities are yet to be understood. Recent studies have suggested that the particle escape might develop with thermal plasma ages of the SNRs. We present a systematic study on the time evolution of particle escape using thermal X-ray properties and gamma-ray spectra using 38 SNRs associated with GeV/TeV gamma-ray emissions. We conducted spectral fittings on the gamma-ray spectra using exponential cutoff power-law and broken power-law models to estimate the exponential cutoff or the break energies, both of which are indicators of particle escape. Plots of the gamma-ray cutoff/break energies over the plasma ages show similar tendencies to those predicted by analytical/numerical calculations of particle escape under conditions in which a shock is interacting with thin interstellar medium or clouds. The particle escape timescale is estimated as ∼100 kyr from the decreasing trends of the total energy of the confined protons with the plasma age. The large dispersions of the cutoff/break energies in the data may suggest an intrinsic variety of particle escape environments. This might be the cause of the complicated Galactic cosmic ray spectral shape measured on Earth.

HIGH-RESOLUTION STUDIES OF GAMMA-RAY SPECTRA USING LITHIUM-DRIFT GERMANIUM GAMMA-RAY SPECTROMETERS

1964 ◽  
Vol 42 (11) ◽  
pp. 2286-2331 ◽  
Author(s):  
G. T. Ewan ◽  
A. J. Tavendale
Keyword(s):  
High Resolution ◽  
Gamma Ray ◽  
High Energy ◽  
Factors Affecting ◽  
Γ Rays ◽  
Γ Ray

This paper describes the use of germanium lithium-drift p-i-n diodes as high-resolution γ-ray spectrometers. With these spectrometers we have obtained γ-ray resolutions of 2.05 keV at 122 keV, 4.0 keV at 1333 keV, and 5.5 keV at 2614 keV. Using the detectors as pair spectrometers for high-energy γ rays, we have obtained a resolution of 9.8 keV on a 7.6-MeV γ ray. The factors affecting the resolution of the detectors are discussed. Fano factors of ~0.4 have been observed. Efficiency curves are given for a 2.5 cm2 × 3.5 mm detector and for a 5 cm2 × 8 mm detector.The detectors have been used to make high-resolution studies of the complex γ-ray spectra from sources of 131Cs, 161Pm, 153Gd, 156Eu, 159Gd, 177Yb, and 226Ra. Results are reported for the energies and intensities of the γ rays observed in these studies.

scholarly journals High-energy Galactic phenomena and the interstellar medium

1985 ◽  
Vol 106 ◽  
pp. 225-233
Author(s):  
Catherine J. Cesarsky
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Small Scale ◽  
The Galaxy ◽  
Γ Rays ◽  
Γ Ray

Gamma rays of energy in the range 30 MeV-several GeV, observed by the satellites SAS-2 and COS-B, are emitted in the interstellar medium as a result of interactions with gas of cosmic-ray nuclei in the GeV range (π° decay γ rays) and cosmic-ray electrons of energy > 30 MeV (bremsstrahlung γ rays). W. Hermsen has presented at this conference the γ ray maps of the Galaxy in three “colours” constructed by the COS-B collaboration; the information in such maps is supplemented by radio-continuum studies (see lecture by R. Beck), and is a useful tool for studying the distribution of gas, cosmic rays (c.r.) and magnetic fields in the Galaxy. The variables in this problem are many:large-scale (~ 1 kpc) and small-scale (~10 pc) distributions of c.r. nuclei, of c.r. electrons, of atomic and molecular hydrogen, of magnetic fields, fraction of the observed radiation due to localized sources, etc. Of these, only the distribution - or at least the column densities - of atomic hydrogen are determined in a reliable way. Estimates of the amount of molecular hydrogen can be derived from CO observations or from galaxy counts. The radio and gamma-ray data are not sufficient to disentangle all the other variables in a unique fashion, unless a number of assumptions are made (e.g. Paul et al. 1976). Still, the COS-B team has been able to show that :a) there is a correlation between the gamma-ray emission from local regions, as observed at intermediate latitudes, and the total column density of dust, as measured by galaxy counts. The simplest interpretation is that the density of c.r. nuclei and electrons is uniform within 500 pc of the sun, and that dust and gas are well mixed. Then, γ rays can be used as excellent tracers of local gas complexes (Lebrun et al. 1982, Strong et al. 1982).b) In the same way, the simplest interpretation of the γ-ray emission at energy > 300 MeV from the inner Galaxy, is that c.r. nuclei and electrons are distributed uniformly as well : there is no need for an enhanced density of c.r. in the 3–6 kpc ring; on the contrary, even assuming a uniform density of c.r., the γ-ray data are in conflict with the highest estimates of molecular hydrogen in the radio-astronomy literature (Mayer-Hasselwander et al. 1982).c) In the outer Galaxy, the gradient of c.r. which had become apparent in the early SAS-2 data can now, with COS-B data, be studied in three energy ranges. A gradient in the c.r. distribution is only required to explain the low-energy radiation, which is dominated by bremsstrahlung from relativistic electrons (Bloemen et al., in preparation).

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