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  • Other Sources  (20)
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  • 1
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    OSSE observations of 1E 1740.7-2942 in 1992 September (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We present data on the galactic X-ray source 1E 1740.7-2942 from the Oriented Scintillation Spectrometer Experiment (OSSE) on board NASA's Compton Gamma Ray Observatory (CGRO). Episodes of increased low-energy gamma radiation have been reported from this source, including 1-day events in 1990 October and 1992 September. These events, of intensity 7 x 10(exp -3) and 4 x 10(exp -3) photons/sq cm/s, respectively, have been interpreted as broadened and redshifted positron annihilation radiation. OSSE conducted observations of the Galactic Center region during a 21-day interval from 1992 September 17 thru 1992 October 8. This includes the time of increased 200-450 keV emission from 1E 1740.7-2942 reported by SIGMA. The OSSE observations do not confirm this event. For the specific outburst recorded by SIGMA, 1992 Sep. 19.42-20.58 (UT), OSSE data provide an upper limit (3 sigma) of 2.4 x 10(exp -3) photons/sq cm/s.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 295; 2; p. L23-L26
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  • 2
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    OSSE observations of galactic 511 keV annihilation radiation (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory has performed several observations of the galactic plane and galactic center region to measure the distribution of galactic 511 keV positron annihilation radiation. Preliminary analysis of data collected during the observation of the galactic center region over the period 13-24 Jun. 1991, indicates the presence of a 511 keV line and positronium continuum superimposed on a power-law continuum. The line of flux was found to be (2.7 +/- 0.5) x 10(exp -4) gamma/sq cm sec, with a positronium fraction of (0.9 +/- 0.2). The 3(sigma) upper limit to daily variations in the 511 keV line flux from the mean during the observation interval is 3 x 10(exp -4) gamma/sq cm sec. If all of the observed annihilation radiation is assumed to originate from the x-ray source 1E 1740.7-2942, the corresponding 511 keV line flux would be (3.0 +/- 0.6) x 10(exp -4) gamma/sq cm sec. The 3(sigma) upper limit for 511 keV line emission from the x-ray binary GX1+4 is 6 x 10(exp -4) gamma/sq cm sec. Results from the galactic plane observations at galactic longitudes of 25 degrees (16-21 Aug. 1991) and 339 degrees (6-11 Sep. 1991) suggest that the emission is concentrated near the galactic center. The observations and the preliminary results are described.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 431-437
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  • 3
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    OSSE observations of the Crab pulsar (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Preliminary results are presented of the Compton Gamma Ray Observatory Oriented Scintillation Spectrometer Experiment (OSSE) observations of the Crab pulsar. The pulsar energy spectra and light curves are in general agreement with previous observations, validating the OSSE pulsar data acquisition modes and data analysis algorithms. The data suggest that the spectrum of the pulsar varies throughout the light curve. The 'interpulse' region has a slightly flatter spectrum in the approx. 60 to 250 keV region and a slightly steeper spectrum at higher energies than the two main pulses. No evidence was found for any lines in the spectra with a typical sensitivity of about 10(exp -4) photons/sq cm/s.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 253-259
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  • 4
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    OSSE spectral analysis techniques (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Analysis of the spectra from the Oriented Scintillation Spectrometer Experiment (OSSE) is complicated because of the typically low signal to noise (approx. 0.1 percent) and the large background variability. The OSSE instrument was designed to address these difficulties by periodically offset-pointing the detectors from the source to perform background measurements. These background measurements are used to estimate the background during each of the source observations. The resulting background-subtracted spectra can then be accumulated and fitted for spectral lines and/or continua. Data selection based on various environmental parameters can be performed at various stages during the analysis procedure. In order to achieve the instrument's statistical sensitivity, however, it will be necessary for investigators to develop a detailed understanding of the instrument operation, data collection, and the background spectrum and its variability. A brief description of the major steps in the OSSE spectral analysis process is described, including a discussion of the OSSE background spectrum and examples of several observational strategies.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 15-25
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  • 5
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    Radioactivity observed in scintillation counters during the HEAO-1 mission (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results are reported from an analysis of radioactivity induced in the NaI medium-energy detector of the hard X-ray and low-energy gamma-ray experiment during the HEAO-1 satellite mission (1977-1978). Consideration is given to the instrument characteristics, the origin and variability of background, and the separation of cosmic-ray activity from the internal activity due to South Atlantic Anomaly trapped protons. Energy spectra and tables listing the nuclide identifications are provided.
    Keywords: SPACE RADIATION
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  • 6
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    Spectra and positions of galactic gamma-ray sources (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The UCSD/MIT Hard X-Ray and Low Energy Gamma-Ray Experiment aboard HEAO-1 scanned the galactic center region during three epochs in 1977 and 1978 from 13 to 180 keV. The results are presented from the scanning epoch of 1978 September. Twenty-two known 2 to 10 keV source positions were necessary for an acceptable fit to the data. The spectra of the 16 strongest, least confused sources are all consistent with power laws with photon spectral indices ranging from 2.1 to 7.2. Acceptable fits to thermal bremsstrahlung models are also possible for most sources. No one source in this survey can be extrapolated to higher energy to match the intensity of the gamma-ray continuum as measured by HEAO-1 large field of view detectors, which implies that the continuum is a composite of contributions from a number of sources.
    Keywords: SPACE RADIATION
    Type: OG-2.5-7 , 19th Intern. Cosmic Ray Conf - Vol. 1; p 217-220; NASA-CP-2376-VOL-1
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  • 7
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    Spectrum of the gamma-ray diffuse component observed from HEAO-1 (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The spectrum of the diffuse X and gamma ray background was measured between 15 keV and 4 MeV with the scintillation detectors aboard the HEAO 1 satellite. The apertures of the detectors were modulated on time scales of hours and the difference in counting rates measured the diffuse component flux. The observed spectrum is presented and compared with other measurements. At least two components are indicated, one below -100 keV and the other above. Possible origins are discussed.
    Keywords: SPACE RADIATION
    Type: OG-3.1-12 , 19th Intern. Cosmic Ray Conf - Vol. 1; p 349-352; NASA-CP-2376-VOL-1
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  • 8
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    Inspecting cracks in foam insulation (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Dye solution indicates extent of cracking by penetrating crack and showing original crack depth clearly. Solution comprised of methylene blue in denatured ethyl alcohol penetrates cracks completely and evaporates quickly and is suitable technique for usage in environmental or structural tests.
    Keywords: MECHANICS
    Type: MFS-23799 , NASA Tech Briefs (ISSN 0145-319X); 4; 1; P. 107
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  • 9
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    The hard X-ray to low-energy gamma-ray spectrum of the Crab Nebula (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Data from the UCSD/MIT Hard X-ray and Low-Energy Gamma-Ray Experiment on the first High Energy Astronomy Observatory (HEAO 1) were used to determine the spectrum of the Crab Nebula in the 10 keV-5 MeV energy range. The spectral change in the 100 keV-1 MeV region is characterized. When the combined spectrum is fitted to a broken power-law model, the data require a description with the following distinct spectral indices: a power-law slope of 2.08 in the 1-100 keV region and a slope of about 2.5 above 150 keV.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 338; 972-982
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  • 10
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    CGRO/OSSE observations of the Cassiopeia A Supernova remnant (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Cassipeia A, the youngest known supernova remnant in the Galaxy and a strong radio and X-ray source, was observed by OSSE 1992 July 16-August 6. Its close distance (approximately 3 kpc) and its young age (approximately 300 yr) make Cas A the best candidate among known supernova remnants for detecting Ti-44 gamma-ray lines. We find no evidence of emission at 67.9 keV, 78.4 keV, or 1.157 MeV, the three strongest Ti-44 decay lines. From simultaneous fits to the three lines our 99% confidence upper limit to the flux in each line is 5.5 x 10(exp -5) gamma/sq cm s. We also report upper limits for the 4.44 MeV C-12 nuclear de-excitation line, which could be produced by interactions of acclerated particles in the supernova remnant, and for the hard X-ray continuum.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 444; 1; p. 244-250
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