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  • 1
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    Hydrogen-deficient atmospheres for cool carbon stars (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Motivated by recent work which hints at a possible deficiency of hydrogen in non-Mira N-type carbon stars and to further explore the parameter space of chemical composition, computations have been made of a series of hydrogen-deficient models for carbon stars. For these models Teff = 3000 K, and log g = 0.0. Solar abundances are used for all elements except for carbon (which is enhanced to give C/O = 1.05), hydrogen, and helium. As the fractional abundance of hydrogen is decreased, being replaced by helium, the temperature-optical depth relation is affected only slightly, but the temperature-pressure relation is changed. The most striking change in the emergent flux is the decrease of the H(-) peak at 1.65 micron compared with the blackbody peak at 1.00 micron.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 228-230
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  • 2
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    Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. IV - Seventeen sources (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: VLBI measurements of time delay and delay rate at 2.29 and 8.42 GHz on baselines of 10,000 km have been used to determine the positions of the milliarcsecond nuclei in 17 extragalactic radio sources with estimated accuracies of 0.1 to 0.3 arcsec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. In addition, slightly improved positions are presented for 101 sources originally reported by Morabito et al. (1983). Arcsecond positions have now been determined for 836 sources.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 92; 546-551
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  • 3
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    Toward a descriptive model of solar particles in the heliosphere (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made.
    Keywords: ASTROPHYSICS
    Type: Interplanetary Particle Environment. Proceedings of a Conference; p 3-13
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  • 4
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    Infrared spectra of WC10 planetary nebulae nuclei (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The 5.2 to 8.0 micron spectra are presented for two planetary nebulae nuclei Hen1044 (He2-113) and CPD-56 8032. The unidentified infrared (UIR) emission bands at 6.2 microns, 6.9 microns, 7.7 microns are present in the spectra of Hen1044 and in CPD-56 8032, and the 8.6 micron band is present in the long wavelength shoulder of the 7.7 micron band in the spectrum of CPD-56 8032. The 8 to 13 micron spectra of these two stars by Aitken et. al. clearly show the presence of the 8.6 micron band in He2-113 while weakly resolving this feature in the spectra of CPD-56 8032. In their spectra the 11.3 micron band is also clearly detected in both objects. The 6.2 micron and 7.7 micron bands are characteristic of the infrared active C-C stretching modes in polycyclic aromatic hydrocarbons (PAHs); the 3.3 micron, 8.6 micron, and 11.3 micron bands are respectively assigned to the in-plane stretching mode, the in-plane bending mode, and the out-of-plane bending mode of the aromatic CH bond. The weak 6.9 micron emission feature is attributed to the UIR spectrum by Bregman et. al. The IRAS LRS spectra of He2-113 (IRAS 14562-5406) and CPD-56 8032 (IRAS 17047-5650) are presented. Cohen et. al. identify the broad plateau from 11.3 to 13.0 microns in the spectrum of He2-113 with increased hydrogenation of PAHs. This broad plateau is not seen in the LRS spectrum of CPD-56 8032. Also, He2-113 has greater infrared excess emission in the 17-22 micron region than does CPD-56 8032.
    Keywords: ASTROPHYSICS
    Type: Summer School on Interstellar Processes: Abstracts of Contributed Papers; p 59-60
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  • 5
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    Filamentary structure in the Orion molecular cloud (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A large scale 13CO map (containing 33,000 spectra) of the giant molecular cloud located in the southern part of Orion is presented which contains the Orion Nebula, NGC1977, and the LI641 dark cloud complex. The overall structure of the cloud is filamentary, with individual features having a length up to 40 times their width. This morphology may result from the effects of star formation in the region or embedded magnetic fields in the cloud. We suggest a simple picture for the evolution of the Orion-A cloud and the formation of the major filament. A rotating proto-cloud (counter rotating with respect to the galaxy) contians a b-field aligned with the galaxtic plane. The northern protion of this cloud collapsed first, perhaps triggered by the pressure of the Ori I OB association. The magnetic field combined with the anisotropic pressure produced by the OB-association breaks the symmetry of the pancake instability, a filament rather than a disc is produced. The growth of instabilities in the filament formed sub-condensations which are recent sites of star formation.
    Keywords: ASTROPHYSICS
    Type: NASA. Ames Research Center Summer School on Interstellar Processes: Abstracts of Contributed Papers; p 29-30
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  • 6
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    Airborne spectrophotometry of Comet Halley from 5 to 9 microns (1986)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: Spectrophotometry from 5 to 9 microns (resolution = 0.02) of comet Halley was obtained from the Kuiper Airborne Observatory on 1985 Dec. 12.1 and 1986 April 8.6 and 10.5 UT. Two spectral features are apparent in all the observations, one from 5.24 to 5.6 microns, and the silicate emission feature which has an onset between 7 and 8 microns. There is no evidence for the 7.5 microns feature observed by the Vega 1 spacecraft; the large difference between the areal coverage viewed from the spacecraft and the airplane may explain the discrepancy. Color temperatures significantly higher than a blackbody indicate that small particles are abundant in the coma. Significant spatial and temporal variations in the spectrum show trends similar to those observed from the ground.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 2: Dust and Nucleus; p 121-124
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  • 7
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    Spectral line profiles of nickel and argon in supernova 1987A - Expansion velocity and electron scattering effects (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Spectra of SN 1987A showing the Ni II 6.634-micron and Ar II 6.983-micron fine-structure lines were obtained from the Kuiper Airborne Observatory in April 1988. The signal-to-noise ratio of 100 near the peaks and resolving power of 200 are sufficient to show the average velocity of expansion from the core of about 1400 km/s and to indicate the range of velocities. An asymmetry in the profiles of both lines and a redshift of the line centroids of about 440 km/s above the 280-km/s recessional velocity of the LMC can be explained in terms of scattering of the photons by electrons in the expanding hydrogen envelope of the supernova. A mass of 0.0030 solar masses of Ni II can be deduced from the line strength of the Ni II line and a mass of 0.0009 solar masses of Ar II from the Ar II line strength.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 338; L9-L12
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  • 8
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    Resolution of the 7.7 micrometers emission feature in NGC 7027 (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The unidentified infrared (UIR) features are a group of emission bands observed in a variety of objects, which can be characterized as having moderate density gas (densities from 1000 to 1,000,000/cu.cm.) and a nearby ultraviolet source. The origin of the features is still uncertain, but the current evidence points to Polycyclic Aromatic Hydrocarbons (PAHs) as the source of the UIR features. Problems with identifying PAHs as the source of the UIR features are discussed.
    Keywords: ASTROPHYSICS
    Type: Summer School on Interstellar Processes: Abstracts of Contributed Papers; p 117-118
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  • 9
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    Radial variations of flow parameters and composition of cold heavy ions within 50,000 km of Halley's nucleus (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Composition and flow parameter of cold heavy ions from the PICCA instrument on Giotto within a cometocentric distance of 50,000 km are presented. A distinct boundary at about 27,000 km, where the flow parameters changed abruptly, is identified and its physical significance is discussed. Radial profiles of heavy ion groups and abundance ratios are given.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 199-201
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  • 10
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    Angular distribution of interstellar Al-26 (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The angular distribution and local concentration of interstellar Al-26 are calculated for five theoretical models of its origin, as a guide for future observations. The models considered relate Al-26 to current star formation (with surface CO density as its indicator), treat Al-26 as a secondary-nucleosynthesis product on seed nuclei with the same metallicity gradient as O, assume the Al-26 ejection rate is proportional to present light output, make Al-26 synthesis depend on total H I + H2 gas density, or assume that Al-26 is formed mainly in novae. The local decay and production rates for the five models are found to lie within a factor of 2 of surface density 0.0003/sq cm s, corresponding to a present (Al-26)/(Al-27) ratio of 5 x 10 to the -6th averaged over H I and H2 phases.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 591-598
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