scholarly journals Gamma-Ray Spectrometry of Galactic Sources in the Energy Range 0.2–3.0 MeV

1971 ◽  
Vol 41 ◽  
pp. 45-57 ◽  
Author(s):  
A Bui-Van ◽  
G. Vedrenne ◽  
P. Mandrou
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Signal To Noise Ratio ◽  
Crab Nebula ◽  
Low Energy ◽  
Gamma Ray Spectrometry ◽  
Angular Aperture ◽  
Energy Gamma ◽  
Galactic Sources ◽  
The Crab Nebula

A low energy gamma-ray telescope (0.2–3 MeV) has been studied in our laboratory. It is made up of an active honeycomb collimator of Nai(T1), with a geometrical angular aperture of 1.5°, and of a detector composed of 73 Nai(T1) sticks (0.5 cm diam.–5 cm length) incorporated in a plastic gabarit used in anticoincidence.The directivity of the telescope is obtained at low energy by the collimator, and at higher energy by the directivity which exists in the gamma-ray interaction through the Compton and photoelectric effects. The electrons emitted in these interactions which are not contained in the sticks of Nai(T1) are detected by the plastic anticoincidence scintillator. Only laboratory tests are presented here, for the study of the galactic gamma-rays, however, the system must subsequently be protected by a 4 cm thick anticoincidence well. In fact the detector directivity enables a great increase in the signal to noise ratio to be expected without greatly increasing the thickness of the shielding.According to the results obtained the estimation of the minimum exposure time for the ‘Crab Nebula’ would be about 2h30m to have a signal at 1 MeV with 2σ of confidence above the background.

A low-energy gamma-ray observation of the Crab Nebula

1977 ◽  
Vol 212 ◽  
pp. 704 ◽  
Author(s):  
P. Mandrou ◽  
M. Niel ◽  
G. Vedrenne ◽  
A. Dupont
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
Low Energy ◽  
Energy Gamma ◽  
The Crab Nebula

scholarly journals Fermi LAT Flare Advocate Activity

2011 ◽  
Vol 7 (S285) ◽  
pp. 294-295 ◽  
Author(s):  
Stefano Ciprini ◽  
Dario Gasparrini ◽  
Denis Bastieri
Keyword(s):  
Gamma Ray ◽  
Galactic Center ◽  
Galactic Plane ◽  
Crab Nebula ◽  
High Energy ◽  
Cherenkov Telescopes ◽  
Duty Cycles ◽  
Energy Gamma ◽  
Galactic Sources ◽  
The Crab Nebula

AbstractThe Fermi Flare Advocate (also known as Gamma-ray Sky Watcher, FA-GSW) service provides a daily quick-look analysis and review of the high-energy gamma-ray sky seen by the Fermi Gamma-ray Space Telescope. The duty offers alerts for potentially new gamma-ray sources, interesting transients and flares. A weekly digest containing the highlights about the GeV gamma-ray sky is published in the web-based Fermi Sky Blog. During the first 3 years of all-sky survey, more than 150 Astronomical Telegrams, several alerts to the TeV Cherenkov telescopes, and targets of opportunity to Swift and other observatories, were realized. That increased the rate of simultaneous multi-frequency observing campaigns and the level of international cooperation. Many gamma-ray flares from blazars (such as extraordinary outbursts of 3C 454.3, intense flares of PKS 1510-089, 4C 21.35, PKS 1830-211, AO 0235+164, PKS 1502+106, 3C 279, 3C 273, PKS 1622-253), short/long flux duty cycles, unidentified transients near the Galactic plane (like J0910-5041, J0109+6134, the Galactic center region), flares associated with Galactic sources (like the Crab nebula, the nova V407 Cyg, the microquasar Cyg X-3), emission of the quiet and active sun, were observed by Fermi and communicated by FA-GSWs.

Measurements of low-energy gamma radiation from the Crab Nebula and from pulsar NP 0532

1975 ◽  
Vol 202 ◽  
pp. 502 ◽  
Author(s):  
G. D. Walraven ◽  
R. D. Hall ◽  
C. A. Meegan ◽  
P. L. Coleman ◽  
D. H. Shelton ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Crab Nebula ◽  
Low Energy ◽  
Energy Gamma ◽  
The Crab Nebula

Detection of High-Energy Gamma Rays from the Crab Nebula

1972 ◽  
Vol 175 ◽  
pp. L117 ◽  
Author(s):  
G. G. Fazio ◽  
H. F. Helmken ◽  
E. O'Mongain ◽  
T. C. Weekes
Keyword(s):  
Gamma Rays ◽  
Crab Nebula ◽  
High Energy ◽  
High Energy Gamma ◽  
Energy Gamma ◽  
The Crab Nebula

scholarly journals Recent Results on the Search for 1011 eV Gamma Rays from the Crab Nebula

1971 ◽  
Vol 46 ◽  
pp. 65-67
Author(s):  
G. G. Fazio ◽  
H. F. Helmken ◽  
G. H. Rieke ◽  
T. C. Weekes
Keyword(s):  
Magnetic Field ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Crab Nebula ◽  
Cosmic Ray ◽  
Air Showers ◽  
Upper Limit ◽  
The Crab Nebula ◽  
Cerenkov Light ◽  
Significant Flux

The detection of Čerenkov light emitted by cosmic-ray air showers was used to search for cosmic gamma rays from the Crab Nebula. By use of the 10-m optical reflector at Mt. Hopkins, Arizona, the Crab Nebula was observed during the winter of 1969–1970 for approximately 112 hours, which was a significant increase in exposure time over previous experiments. Above a gamma-ray energy of 2.2 × 1011 eV, no significant flux was detected, resulting in an upper limit to the flux of 8.1 × 10-11 photon/cm2 sec. In the synchrotron-Compton-scattering model of gamma-ray production in the Crab Nebula, this limit on the flux indicates the average magnetic field in the nebula must be greater than 3 × 10-4 G.

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