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  • 1
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    Centaurus A, the core of the problem (1994)
    In:  Other Sources
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    Publikationsdatum: 2019-01-25
    Beschreibung: The bright, peculiar elliptical galaxy Centaurus A (NGC 5128, PKS 1322-427) was one of the first extragalactic radio sources to be optically identified (Bolton et al. 1949). At a distance of 4 Mpc, Centaurus A is the closest active radio galaxy and affords the highest linear imaging resolution (1 mas approximately equal to 0.02 pc) and hence the best prospects for studying an active nucleus close to the central radio source. We present the results of multi-epoch, 8.4-GHz, very long baseline interferometry (VLBI), imaging observations of the nucleus made over the past three years. The nucleus possesses a core-jet structure where the inner portion of the jet shows apparent linear motion with a velocity substantially less than the speed of light.
    Schlagwort(e): ASTRONOMY
    Materialart: Australian Journal of Physics (ISSN 0004-9506); 47; 5; p. 619-624
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  • 2
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    The southern hemisphere VLBI experiment (SHEVE) (1988)
    In:  Other Sources
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    Publikationsdatum: 2019-07-13
    Beschreibung: Six radio telescopes were operated as the first southern hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 Ghz. This array produced VLBI images of 28 southern hemisphere radio sources, high accuracy VLBI geodesy between southern hemisphere sites, and sub-arcsecond radio astrometry of celestial sources south of declination -45 degrees. This paper discusses only the astrophysical aspects of the experiment.
    Schlagwort(e): ASTRONOMY
    Materialart: IAU Symposium on the Impace of VLBI on Astrophysics and Geophysics; May 10, 1987 - May 15, 1987; Cambridge, MA; United States
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  • 3
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    Radio observations of SN 1987A (1988)
    In:  Other Sources
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    Publikationsdatum: 2019-07-13
    Beschreibung: The study of radio emission from SN 1987A after the neutrino burst is reviewed. The observed maximum flux density of the burst at radio wavelengths was about 140 mJy and occurred at 1.4 GHz. The radio light curves for SN 1987A at four frequencies are compared with data for SN 1979C and SN 1980K. VLBI observations of SN 1987A at 2.3 GHz and other radio monitoring programs are examined.
    Schlagwort(e): ASTRONOMY
    Materialart: Geroge Mason Astrophysics Workshop; Oct 12, 1987 - Oct 14, 1987; Fairfax, VA; United States
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  • 4
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    The unusual morphology of molecular hydrogen emission in the planetary nebula J900 (1995)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: We report new high-resolution near-infrared imaging observations of the planetary nebula J900, in broadband J, H, and K, and narrowband 2.122 micrometers (for H2 1-0 S(1)), Brackett-gamma, and continuum filters. The H2 images reveal a remarkable set of outward-extending features not detected in any previous observations of theis object. In the northwest lobe of the inner bipolar region, the H2 emission, Brackett-gamma emission, and underlying continuum are spatially resolved. The relative positions of the peaks of the line emission suggest an ionization front seen edge-on. The continuum emission, apparently located nearer to the central star, is likely due to transiently heated small dust grains. The extended H2 emission features are probably excited either by oblique shocks caused by material ejected from the nebula, or by radiation leaking from holes in the opacity surrounding the ionized shell.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 109; 3; p. 1173-1180
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  • 5
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    Asteroid team (1986)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: Work on asteroid classification continued was rewarded with the discovery of two Earth-approaching M asteroids. The M class is rare and these are the first found among the near-Earth asteroids to have the spectral albedo characteristic of this class. The two asteroids are newly discovered 1986 DA and 1986 EB which were observed at N and Q bandpasses (i.e., 10 and 20 microns) with the 3 m IRTF telescope and at five wavelengths from 0.36 to 0.85 microns from Kitt peak National Observatory's 0.36 m telescope. The derived diameters are about 2 km for both objects. In the asteroid radiometry program N or Q photometry was obtained for more than 40 asteroids in Feb. 1986. Radiometric diameter calibration support were provided for stellar occultations of stars by 230 Athamantis and 129 Antigone. The data were reduced but not analyzed. Infrared spectra (0.8 to 2.6 microns) of 60 asteroids were reduced and are now ready for compositional analysis.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Reports of Planetary Astronomy, 1985; p 104
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  • 6
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    The project EGRET (Energetic Gamma-Ray Experiment Telescope) on NASA's Gamma-Ray Observatory (GRO) (1988)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The design, predicted performance, and scientific objectives of the 20-30,000-MeV gamma-ray telescope EGRET for the NASA GRO spacecraft (scheduled for Space Shuttle launch to a 450-km 28.5-deg orbit in 1990) are reviewed. The other GRO instruments are briefly characterized, including the burst and transient-source experiment, the oriented scintillation spectrometer, and the imaging Compton telescope. EGRET comprises an anticoincidence system, a spark chamber, a triggering telescope, an NaI total-absorption spectrometer, a gas supply capable of refilling the chamber four times, and support electronics. EGRET will operate with energy resolution about 15 percent, effective area about 2000 sq cm, sensitivity about 5 x 10 to the -8th/sq cm sec, angular resolution 0.1-0.4 deg, and FOV about 40 deg FWHM. Observations of Galactic point sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, and solar flares are planned.
    Schlagwort(e): ASTRONOMY
    Materialart: Space Science Reviews (ISSN 0038-6308); 49; 1-2,
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  • 7
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    The Gamma-Ray Observatory mission objectives and its significance for gamma-ray astronomy (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Gamma Ray Observatory (GRO) is an approved NASA mission, programmed for launch in 1988. Its complement of four detectors has established goals: (1) to study the nature of compact gamma-ray sources such as neutron stars and black holes, or objects whose nature is yet to be understood; (2) to search for evidence of nucleosynthesis especially in the regions of supernovae; (3) to study structural features and dynamical properties of the Galaxy; (4) to explore other galaxies, especially the extraordinary types such as radio, Seyferts, and quasars; and (5) to study cosmological effects by examining the diffuse radiation in detail. This paper discusses the design, objectives, and expected scientific results of each of the GRO instruments in view of the GRO mission goals.
    Schlagwort(e): ASTRONOMY
    Materialart: Advances in Space Research (ISSN 0273-1177); 3; 10-12
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  • 8
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    A search at the millijansky level for milli-arcsecond cores in a complete sample of radio galaxies (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A complete sample of 26 extended radio galaxies was observed at 2.29 GHz with the Mark III VLBI system. The fringe spacing was about 3 milli-arcsec, and the detection limit was about 2 millijanskys. Half of the galaxies were found to possess milli-arcsec radio cores. In all but three sources, the nuclear flux density was less than 0.04 of the total flux density. Galaxies with high optical luminosity (less than -21.2) were more likely than less luminous galaxies to contain a detectable milliparcsec radio core (69 percent vs. 20 percent). For objects with arcsec cores, 80 percent were found to have a milli-arcsec core, even though the milli-arcsec object did not always contribute the greater part of the arcsec flux density.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 519-522
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  • 9
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    IRAS observations of comets (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The moderate spatial resolution and high sensitivity of the Infrared Astronomical Satellite (IRAS), which surveyed the celestial sphere during 1983 at wavelengths of 12, 25, 60, and 100 microns, were particularly well suited to detecting extended thermal emission from cometary dust. Sources with infrared color temperatures characteristic of solar system bodies, and at the ephemerides position of known comets were selected for analysis by the IRAS Asteroid Data Analysis System (ADAS). The data base is now available for use by researchers. This paper describes the development of the data base, details its entries, and presents a statistical analysis of its contents. The IRAS survey contains multiple observations of many periodic comets. A brief description and analysis is given of the observed infrared and derived physical properties for several comets of special interest.
    Schlagwort(e): ASTRONOMY
    Materialart: Advances in Space Research (ISSN 0273-1177); 6; 7, 19
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  • 10
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    IRAS survey of asteroids (1986)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The Infrared Astronomical Satellite (IRAS) scanned the celestial sphere during 1983 through bandpasses centered at wavelengths of 12, 25, 60 and 100 microns. In addition to sources fixed on the sky, many moving objects were observed. This data set is the largest and least biased survey of asteroids and comets ever conducted. Included are main belt asteroids, Mars-crossers, earth-approachers, and Trojans. Measurements for the known asteroids have been reduced and organized into a number of data products which are available to researchers. The data for 'new' asteroids are being processed.
    Schlagwort(e): ASTRONOMY
    Materialart: Advances in Space Research (ISSN 0273-1177); 6; 7, 19
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