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Gamma-ray fluxes (1972)

Kniffen, D. A.

In: CASI

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Publication Date: 2005-11-30

Description: The design and development of detectors to analyze gamma rays greater than 20 MeV are reported. Efforts were made to identify and verify the existence of galactic gamma radiation from the galactic disc, provide information on its spectral and spatial distribution, and determine the source of gamma ray emission from the galactic plane in the direction of the galactic center. Results verify the existence of gamma radiation from the galactic disc, indicate that limits are placed on the angular width of observed line intensity, and indicate a probable flattening of the energy below 100 MeV.

Keywords: SPACE SCIENCES

Type: Significant Accomplishments in Sci., 1970; p 204-208

Format: text

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2

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Gamma-ray observations of the galactic center and some possible point sources. (1972)

Fitchtel, C. E. ; Hartman, R. C. ; Sommer, M. ; [et al.]

In: Other Sources

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Publication Date: 2011-08-16

Description: A 0.5 x 0.5-m digitized spark-chamber gamma-ray telescope was flown on three balloon flights to look at the galactic center region, Virgo, and the Crab Nebula. An excess flux above atmospheric background of over 4 standard deviations was found for gamma-rays exceeding 100 MeV coming from the galactic center region, but there was no statistically significant excess in the 50-100 MeV interval. As a result, there is only a 6% chance that Compton or synchrotron radiation from electrons with a power-law spectrum having an exponent of 2.6 could make as much as a 50% contribution to the gamma-radiation in this energy range.

Keywords: SPACE SCIENCES

Type: Astrophysical Journal; 171; Jan. 1

Format: text

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3

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Gamma ray astronomy (1974)

Kniffen, D. ; Fichtel, C. E.

In: Other Sources

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Publication Date: 2011-08-16

Description: The various source mechanisms for celestial gamma rays are reviewed. The gamma-ray data are examined as a source of information about the processes and source locations for the production of charged particle cosmic rays, galactic structure, explosive nucleosynthesis in supernovae, regions of confinement for cosmic rays, regions where matter-antimatter annihilation occurs, and the general condition in cosmological space both in the past and present. Topics include gamma rays from pi mesons by nuclear interactions, nuclear and supernovae lines, diffuse emission and discrete sources, interstellar absorption and detection of gamma rays, and others. A brief view of the available gamma-ray detection systems and techniques is presented.

Keywords: SPACE SCIENCES

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4

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A Systematic Search for Short-term Variability of EGRET Sources (2000)

Thompson, D. J. ; Griffis, N. J. ; Hartman, R. C. ; [et al.]

In: CASI

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Publication Date: 2013-08-29

Description: The 3rd EGRET Catalog of High-energy Gamma-ray Sources contains 170 unidentified sources, and there is great interest in the nature of these sources. One means of determining source class is the study of flux variability on time scales of days; pulsars are believed to be stable on these time scales while blazers are known to be highly variable. In addition, previous work has demonstrated that 3EG J0241-6103 and 3EG J1837-0606 are candidates for a new gamma-ray source class. These sources near the Galactic plane display transient behavior but cannot be associated with any known blazers. Although, many instances of flaring AGN have been reported, the EGRET database has not been systematically searched for occurrences of short-timescale (approximately 1 day) variability. These considerations have led us to conduct a systematic search for short-term variability in EGRET data, covering all viewing periods through proposal cycle 4. Six 3EG catalog sources are reported here to display variability on short time scales; four of them are unidentified. In addition, three non-catalog variable sources are discussed.

Keywords: Astrophysics

Format: application/pdf

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