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  • ASTRONOMY  (60)
  • ENERGY PRODUCTION AND CONVERSION
  • SOLAR PHYSICS
  • 1990-1994  (115)
  • 1980-1984
  • 1993  (115)
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  • 1990-1994  (115)
  • 1980-1984
Year
  • 1
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    Gamma radiation from blazar PKS 0537-441 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) observed high-energy gamma rays from PKS 0537-441 during observations in 1991 July-August. Upper limits from later EGRET observations suggest time variability.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 410; 1; p. 87-89.
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  • 2
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    SCR neon and argon in Kapoeta feldspar: Evidence for an active ancient Sun (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: From etched feldspar size-fractions of Kapoeta, we determine a significant excess of cosmogenic Ne-21 and Ar-38 over that produced by galactic cosmic rays. This excess component is attributed to early production by energetic solar protons and suggest that the energetic proton flux from the ancient Sun was several hundred times more intense than that of the contemporary Sun.
    Keywords: SOLAR PHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1193-1194
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  • 3
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    Results from the energetic gamma-ray experiment telescope (EGRET) on the Compton Observatory (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud (LMC) having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's
    Keywords: ASTRONOMY
    Type: Advances in Space Research (ISSN 0273-1177); 13; 12; p. (12)637-(12)646
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  • 4
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    Solar-flare implanted He-4/He-3 and solar-proton-produced Ne and Ar concentration profiles preserved in lunar rock 61016 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Depth profiles for Ne-21, Ne-22, and Ar-38 isotopes from oriented lunar rock 61016 are reported. Concentration profiles of cosmogenic GCR+SCR (Galactic cosmic ray and solar cosmic ray-produced) isotopes are determined, quantitatively resolving neon and argon produced by energetic solar flares from that produced by Galactic cosmic rays. The SCR component is resolved from the GCR component as a function of shielding, and excellent agreement is found between experimental SCR production profiles for the isotopes and theoretically calculated values. A characteristic SW He-4/He-3 ratio of 3450 +/- 81, representing energies down to as few keV/amu. In slightly deeper samples an SRF He-4/He-3 ratio of 3450 +/- 725 is found for He particles with E larger than about 1 MeV/amu. These results indicate that the isotopic composition of SF He, averaged over the long term, is energy-dependent. An implanted Ne-20/Ne-22 ratio of 12.4 is measured in unetched samples, representing E greater than 1 MeV/amu, and a ratio of 11.6 is inferred in the samples, representing E larger than about 5 MeV/amu.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A5; p. 7827-7835.
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  • 5
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    Direct 75 milliarcsecond images from the Multiple Mirror Telescope with adaptive optics (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report results from an adaptive optics system designed to provide imaging at the diffraction limit of resolution in the near-infrared at the Multiple Mirror Telescope (MMT). For the present experiment, the aperture consisted of five of the six primary mirrors of the MMT, operating as a coherently phased array. The largest components of the atmospherically induced wave-front aberration are the fluctuations in mean phase between the segments. These errors were derived in real time from the Fourier transform of short-exposure stellar images at 2.2 microns and corrected at an image of the telescope pupil with piston motion from a segmented adaptive mirror. At a correction rate of 43 Hz, this level of adaptive control resulted in an integrated image with a clear diffraction-limited component of 0.075 arcsec FWHM. This stabilized component is present directly in the light arriving at the detector and is not the result of postprocessing. We discuss future improvements to our adaptive wave-front control and its application to astronomical observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 402; 2; p. L81-L84.
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  • 6
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    Detection of a long-duration solar gamma-ray flare on June 11, 1991 with EGRET on COMPTON-GRO (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The detection of high energy photon emission from a long-duration solar gamma-ray flare on June 11, 1991 is reported. Gamma rays were detected up to energies above 1 GeV. The solar origin of this emission is assured by the time profile of the gamma-ray count rate and by time-resolved sky maps, which show a clear maximum at the position of the sun. There are indications for a spectral evolution with time, such that the emission below 100 MeV fades away earlier than the 100-300 MeV radiation, roughly on the time scale of the fast component. The spectrum of the flare can be well fitted with a composite of a proton generated pi exp 0 spectrum and an electron bremsstrahlung component. The latter can be identified with the fast decaying component of the lightcurve.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 97; 1; p. 349-353.
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  • 7
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    EGRET observations of 3C 273 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The quasar 3C 273 was detected by COS-B in the 1970's. EGRET observations of this sky region in June and October 1991 revealed a flux from 3C 273 lower than that measured by COS-B. The flux observed by EGRET in the June period is approximately 3 x 10 exp -7/sq cm s for energies greater than 100 MeV. During the October observation it appears to be even lower. For the first observation a preliminary spectrum which has a photon index of 2.4 has been derived.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 97; 1; p. 101-103.
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  • 8
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    Twenty-two emission-line AGNs from the HEAO-1 X-ray survey (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report 22 emission-line AGN as bright, hard X-ray sources. All of them appear to be new classifications with the exception of one peculiar IRAS source which is a known quasar and has no published spectrum. This sample exhibits a rich diversity in optical spectral properties and luminosities, ranging from a powerful broad-absorption-line quasar to a weak nucleus embedded in a nearby NGC galaxy. Two cases confer X-ray luminosities in excess of 10 exp 47 erg/s. However, there is a degree of uncertainty in the X-ray identification for the AGN fainter than V about 16.5. Optically, several AGN exhibit very strong Fe II emission. One Seyfert galaxy with substantial radio flux is an exception to the common association of strong Fe II emission and radio-quiet AGN. The previously recognized IRAS quasar shows extreme velocities in the profiles of the forbidden lines; the 0 III pair is broadened to the point that the lines are blended. Several of these AGN show evidence of intrinsic obscuration, illustrating the effectiveness of hard X-ray surveys in locating AGN through high column density.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 105; 6; p. 2079-2089, 2363-2
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  • 9
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    Observations of the Crab pulsar and nebula by the EGRET telescope on the Compton Gamma-Ray Observatory (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Crab pulsar and nebula were observed three times in 1991 April to June by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO): April 23 to May 7, May 16 to 30, and June 8 to 15. The results of analysis of the gamma-ray emission in the energy range from 50 MeV to more than 10 GeV are reported. The observed gamma-ray light curve exhibits two peaks separated in phase by 0.40 +/- 0.02, consistent with previous observations. The total pulsed emission from the Crab pulsar is found to be well represented by a power-law spectrum, softer than the spectrum measured by COS B (Clear et al., 1987). The interpulse emission has a harder spectrum than either of the pulses. The evidence for pulsed emission above 5 GeV in the EGRET data is not conclusive. Unpulsed emission in the energy range 50 MeV to 5 GeV was detected, with an indication of a hardening of the unpulsed spectrum above about 1 GeV. There was a significant change in the light curve over the 2 months of these observations, although the shape of the spectrum remained constant.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 409; 2; p. 697-704.
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  • 10
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    Cassini radio and plasma wave investigation - Data compression and scientific applications (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Radio and Plasma Wave Science (RPWS) experiment being built for the Cassini spacecraft will study a wide range of plasma and radio wave phenomena in the magnetosphere of Saturn and will also make valuable measurements during the cruise phase and at other encounters. A feature of data from wave receivers is the capability of producing vastly more data than the spacecraft telemetry link is capable of transmitting back to the Earth. Thus, techniques of on-board data compression and data reduction are important. The RPWS instrument has one processor dedicated to data compression tasks.
    Keywords: SOLAR PHYSICS
    Type: British Interplanetary Society, Journal (ISSN 0007-094X); 46; 3; p. 115-120.
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