scholarly journals Gamma-ray emission from high Galactic latitude globular clusters

2018 ◽  
Author(s):  
Sheridan J Lloyd ◽  
Paula M Chadwick ◽  
Anthony M Brown
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Galactic Latitude ◽  
High Galactic Latitude ◽  
Gamma Ray Emission

scholarly journals Gamma-ray emission from globular clusters 2MS-GC01, IC 1257, FSR 1735, NGC 5904 and 6656

2015 ◽  
Vol 448 (4) ◽  
pp. 3215-3220 ◽  
Author(s):  
J. N. Zhou ◽  
P. F. Zhang ◽  
X. Y. Huang ◽  
X. Li ◽  
Y. F. Liang ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Gamma Ray Emission

EGRET upper limits to the high-energy gamma-ray emission from the millisecond pulsars in nearby globular clusters

1994 ◽  
Vol 435 ◽  
pp. 218 ◽  
Author(s):  
P. F. Michelson ◽  
D. L. Bertsch ◽  
K. Brazier ◽  
J. Chiang ◽  
B. L. Dingus ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
High Energy ◽  
Millisecond Pulsars ◽  
High Energy Gamma ◽  
Upper Limits ◽  
Energy Gamma ◽  
Gamma Ray Emission

scholarly journals Modelling the Multifrequency SED of AGN Candidates among the Unidentied EGRET and Fermi Gamma-Ray Sources

2014 ◽  
Vol 1 (1) ◽  
pp. 163-169
Author(s):  
Pieter J. Meintjes ◽  
Pheneas Nkundabakura ◽  
Brian Van Soelen ◽  
Alida Odendaal
Keyword(s):  
Gamma Ray ◽  
Radio Galaxy ◽  
Radio Galaxies ◽  
Galactic Latitude ◽  
Large Telescope ◽  
High Galactic Latitude ◽  
New Class ◽  
Multi Wavelength ◽  
One Year

Of the 271 sources in the 3rd EGRET catalogue, 131 were reported as unidentied, i.e. not associated with any particular class of point source in the sky. Since the largest fraction of the EGRET sources were extragalactic, a sample of 13 extragalactic unidentied sources have been selected for multi-wavelength follow-up studies. Five of the selected EGRET sources coincide with gamma-ray flux enhancements seen in the Fermi-LAT data after one year of operation. In this article, we report the multi-wavelength properties of, among others, the 5 sources detected by Fermi-LAT from our sample of high galactic latitude unidentied EGRET sources. Recent spectroscopic observations with the Southern African Large Telescope (SALT) conrmed one of the unidentied EGRET sources as a possible Seyfert 2 galaxy, or alternatively, a narrow line radio galaxy. The detected gamma-ray emission (E<sub>γ</sub> &gt; 30 MeV) of the 5 coinciding EGRET/Fermi-LAT sources are tted with external Compton and Synchrotron Self Compton (SSC) models to investigate the energetics required to produce the EGRET/Fermi gamma-ray flux. In all the models the inclination angle of the jet with respect to the observer is jet 60, between those of Seyfert 1 and Seyfert 2/radio galaxies. These results confirm the possibility of Seyfert and radio galaxies sources are constituting a new class of gamma-ray source in the energy range E<sub>γ</sub> &gt; 30 MeV.

scholarly journals Gamma-ray Emission from Globular Clusters

2016 ◽  
Vol 33 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Pak-Hin T. Tam ◽  
Chung Y. Hui ◽  
Albert K. H. Kong
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Gamma Ray Emission

scholarly journals GAMMA-RAY EMISSION FROM THE GLOBULAR CLUSTERS LILLER 1, M80, NGC 6139, NGC 6541, NGC 6624, AND NGC 6752

2011 ◽  
Vol 729 (2) ◽  
pp. 90 ◽  
Author(s):  
P. H. T. Tam ◽  
A. K. H. Kong ◽  
C. Y. Hui ◽  
K. S. Cheng ◽  
C. Li ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Gamma Ray Emission

scholarly journals Galactic diffuse gamma-ray emission at TeV energy

2020 ◽  
Vol 633 ◽  
pp. A94 ◽  
Author(s):  
A. Neronov ◽  
D. Semikoz
Keyword(s):  
Emission Spectrum ◽  
Gamma Ray ◽  
Galactic Plane ◽  
Cosmic Ray ◽  
Galactic Latitude ◽  
Diffuse Emission ◽  
Large Area ◽  
High Galactic Latitude ◽  
Galactic Emission ◽  
Significant Difference

Context. Measuring the diffuse Galactic γ-ray flux in the TeV range is difficult for ground-based γ-ray telescopes because of the residual cosmic-ray background, which is higher than the γ-ray flux by several orders of magnitude. Its detection is also challenging for space-based telescopes because of low signal statistics. Aims. We characterise the diffuse TeV flux from the Galaxy using decade-long exposures of the Fermi Large Area Telescope. Methods. Considering that the level of diffuse Galactic emission in the TeV band approaches the level of residual cosmic-ray background, we estimated the level of residual cosmic-ray background in the SOURCEVETO event selection and verified that the TeV diffuse Galactic emission flux is well above the residual cosmic-ray background up to high Galactic latitude regions. Results. We study spectral and imaging properties of the diffuse TeV signal from the Galactic plane. We find much stronger emission from the inner Galactic plane than in previous HESS telescope estimates (lower bound). We also find a significant difference in the measurement of the Galactic longitude and latitude profiles of the signal measured by Fermi and HESS. These discrepancies are presumably explained by the fact that regions of background estimate in HESS have non-negligible γ-ray flux. Comparing Fermi measurements with those of ARGO-YBJ, we find better agreement, with the notable exception of the Cygnus region, where we find much higher flux (by a factor 1.5). We also measure the TeV diffuse emission spectrum up to high Galactic latitude and show that the spectra of different regions of the sky have spectral slopes consistent with Γ = 2.34 ± 0.04, which is harder than the slope of the locally observed spectrum of cosmic rays with energies 10–100 TeV, which produce TeV diffuse emission on their way through the interstellar medium. We discuss the possible origin of the hard slope of the TeV diffuse emission. Conclusions. Fermi/LAT provides reliable measurements of the diffuse Galactic emission spectrum in the TeV range, which are almost background free at low Galactic latitudes. The diffuse flux becomes comparable to the residual cosmic-ray background at Galactic latitudes |b| > 50°. Its measurement in these regions might suffer from systematic uncertainty stemming from the uncertainty of our phenomenological model of the residual cosmic-ray background in the Pass 8 Fermi/LAT data.

scholarly journals Detection of gamma-ray emission from globular clusters M15, NGC 6397, 5904, 6218 and 6139 withFermi-LAT

2016 ◽  
Vol 459 (1) ◽  
pp. 99-107 ◽  
Author(s):  
P. F. Zhang ◽  
Y. L. Xin ◽  
L. Fu ◽  
J. N. Zhou ◽  
J. Z. Yan ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Gamma Ray Emission
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