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  • ASTROPHYSICS  (7,633)
  • 1985-1989  (4,662)
  • 1980-1984  (2,970)
  • 1960-1964  (1)
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  • 1
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    Meteoritics (1964)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Keywords: ASTROPHYSICS
    Type: NASA-TT-F-100 , NAS 1.77:F-100 , AD-A276988
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  • 2
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    Binary models for the progenitor of SN 1987A (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Binary models are used to examine the possibility that the progenitor of SN 1987 is a component of a binary system. Certain ranges of parameter space in which binary evolution produces progenitors that are applicable to models of SN 1987A are considered. The proposed binary models are capable of making definite predictions that can be checked against observations.
    Keywords: ASTROPHYSICS
    Type: ; : Visual information
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  • 3
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    Gamma ray astrophysics to the year 2000. Report of the NASA Gamma Ray Program Working Group (1988)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Important developments in gamma-ray astrophysics up to energies of 100 GeV during the last decade are reviewed. Also, the report seeks to define the major current scientific goals of the field and proposes a vigorous program to pursue them, extending to the year 2000. The goals of gamma-ray astronomy include the study of gamma rays which provide the most direct means of studying many important problems in high energy astrophysics including explosive nucleosynthesis, accelerated particle interactions and sources, and high-energy processes around compact objects. The current research program in gamma-ray astronomy in the U.S. including the space program, balloon program and foreign programs in gamma-ray astronomy is described. The high priority recommendations for future study include an Explorer-class high resolution gamma-ray spectroscopy mission and a Get Away Special cannister (GAS-can) or Scout class multiwavelength experiment for the study of gamma-ray bursts. Continuing programs include an extended Gamma Ray Observatory mission, continuation of the vigorous program of balloon observations of the nearby Supernova 1987A, augmentation of the balloon program to provide for new instruments and rapid scientific results, and continuation of support for theoretical research. Long term recommendations include new space missions using advanced detectors to better study gamma-ray sources, the development of these detectors, continued study for the assembly of large detectors in space, collaboration with the gamma-ray astronomy missions initiated by other countries, and consideration of the Space Station attached payloads for gamma-ray experiments.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-107995 , NAS 1.15:107995
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  • 4
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    The composition of comets (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The present discussion of recent studies concerning cometary composition gives attention to the results obtained by in situ measurements of Comet Halley's dust composition by Vega 1's impact mass spectrometer, which discovered a mineral fraction that appears to be CI chondritic, as well as an organic fraction consisting of highly unsaturated hydrocarbons. The mineral fraction of comets appears to form a core that is embedded in essentially organic material; the spectroscopic invisibility of carbon is due to its presence in the cometary dust. The mass of most dust particles is found to be in the 10 to the -12th to 10 to the -14th g range. A considerable fraction of the dust grains serves as an extended source of gas in the inner coma.
    Keywords: ASTROPHYSICS
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  • 5
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    Comet Halley: The view from Pioneer Venus (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The plans to scan Halley's Comet at close range using the Pioneer Venus Orbiter are discussed. The composition of comets, their paths through space, and the history of comet encounters are examined. An ultraviolet spectrometer aboard the spacecraft will determine the composition of the gaseous coma and will measure the total gas production during its passage. The Pioneer Venus Orbiter will observe the comet for five weeks before solar interference with communications occurs as Venus passes on the far side of the Sun from Earth. Diagrams of the solar system and the relationship of the comet to the planets and the Sun are provided.
    Keywords: ASTROPHYSICS
    Type: NASA-NF-127 , NAS 1.20:127
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  • 6
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    Gravitational lensing in a cold dark matter universe (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Gravitational lensing due to mass condensations in a biased cold dark matter (CDM) universe is investigated using the Press-Schechter (1974) theory with density fluctuation amplitudes taken from previous N-body work. Under the critical assumption that CDM haloes have small core radii, a distribution of image angular separations for high-z lensed quasars with a peak at about 1 arcsec and a half-width of a factor of about 10. Allowing for selection effects at small angular separations, this is in good agreement with the observed separations. The estimated frequency of lensing is somewhat lower than that observed, but the discrepancy can be removed by invoking amplification bias and by making a small upward adjustment to the density fluctuation amplitudes assumed in the CDM model.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 231; 97p-103p
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  • 7
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    Astrophysics (1986)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The instrumentation, accomplishments and future activities in space astrophysics observations are explored. The Solrad, Orbiting Solar Observatory, Solar Maximum Mission, Orbiting Astronomical Observatory, Extreme Ultraviolet Explorer, Uhuru, HEAO-2, IRAS and ESA SAS spacecraft missions and data are summarized. Observations which identified the black hole in Cygnus-1 are described and known gravity-controlled phenomena in the universe are reviewed. Observations at different electromagnetic wavelengths and by particle detectors are outlined, and proposed gravity wave and neutrino detectors are discussed. The implications of the angular, spectral and temporal resolution, polarization, spectral range and observational limits of the instrumentation and data are considered. Current topics of interest in studies of the cosmic background radiation, distance scales, quasars and pulsars, star formation, and coronal heating are outlined. Finally, the design features and observational goals of the NASA Great Observatories space platforms are described.
    Keywords: ASTROPHYSICS
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  • 8
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    Ultraviolet and infrared observations of stars with 'quenched' chromospheres and the nature of mass loss (1986)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Previous observational evidence implies that the presence of Ca II emission, a chromospheric indicator, is correlated with the gas/dust ratio in the envelopes of red giant and supergiant stars. An attempt is made to determine whether this correlation can be generalized to all chromospheric activity indicators and the gas/dust ratio. New ultraviolet observations address the strength of UV emission features and the fraction of the total chromospheric flux emitted in various lines. Evidence is found that chromospheres are not completely quenched in the presence of dust, but that significant alteration of relative radiative loss patterns may occur. These observations are interpreted in terms of an instability that converts warm, chromospheric gas into near-surface dust grains and cool gas capable of supporting molecular masing. This supports the dust-driven mass loss scenario for red giant winds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 308; 859-867
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  • 9
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    The 1979 X-ray outburst of Centaurus X-4 (1980)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: X-ray observations of the first major outburst of the classical transient X-ray source Centaurus X-4 since its discovery in 1969 are presented. The observations were obtained in May, 1979, with the all-sky monitor on board Ariel 5. The flare light curve is shown to exhibit many of the characteristics of other transients, including a double-peaked maximum, as well as significant, apparently random, variations and a lower peak flux and shorter duration than the 1969 event. Application of a standard epoch-folding technique to data corrected for linear decay trends indicates a possible source modulation at 0.3415 days (8.2 hours). Comparison of the results with previous other data on Cen X-4 and the characteristics of the soft X-ray transients allows a total X-ray output of approximately 3 x 10 to the 43rd ergs to be estimated, and reveals the duration and decay time of the 1979 Cen X-4 outburst to be the shortest yet observed from soft X-ray transients. The observations are explained in terms of episodic mass exchange from a late-type dwarf onto a neutron star companion in a relatively close binary system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 10
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    Evaluation of orbits with incomplete knowledge of the mathematical expectancy and the matrix of covariation of errors (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The problem of selecting the optimal algorithm of filtration and the optimal composition of the measurements is examined assuming that the precise values of the mathematical expectancy and the matrix of covariation of errors are unknown. It is demonstrated that the optimal algorithm of filtration may be utilized for making some parameters more precise (for example, the parameters of the gravitational fields) after preliminary determination of the elements of the orbit by a simpler method of processing (for example, the method of least squares).
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76237
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  • 11
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    Space superbubble 1200 light years across (1980)
    In:  CASI
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    Publication Date: 2019-08-28
    Keywords: ASTROPHYSICS
    Type: NASA-NEWS-RELEASE-80-3 , P80-10003
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  • 12
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    Nature of type 1 Supernovae (1980)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The nature of type 1 supernovae (SN 1) is discussed through a comparison of observational evidence and theoretical perspectives relating to both type 1 and 2 supernovae. In particular two hypotheses relating to SN 1 phenomenon are examined: the first proposing that SN 1 are components of binary systems in which, at a comparatively late stage of evolution, overflow of the mass occurs; the second considers pre-SN 1 to be recently evolved stars with a mass greater than 1.4 solar mass (white dwarfs). In addition, an explanation of the reduced frequency of flares of SN 1 in spiral galaxies as related to that in elliptical galaxies is presented.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76238 , PR-395
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  • 13
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    Review of results on Halley's comet (1987)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Since its recovery in 1982, Comet Halley has been the focus of an unparalleled global scientific effort of exploration. Remote and in situ measurements were conducted from the ground, from earth orbit, from Venus orbit, from interplanetary space, and from the comet itself. Many discoveries, such as the presence of an unexpectedly large and dark nucleus or the abundance of organic material, have led to major changes in the ideas about the general nature of comets. In this report, results of various studies are summarized.
    Keywords: ASTROPHYSICS
    Type: European Regional Astronomy Meeting of the IAU; Aug 24, 1987 - Aug 29, 1987; Prague; Czechoslovakia
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  • 14
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    The M-type stars (1987)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The papers in this volume cover the following topics: (1) basic properties and photometric variability of M and related stars; (2) spectroscopy and nonthermal processes; (3) circumstellar radio molecular lines; (4) circumstellar shells, the formation of grains, and radiation transfer; (5) mass loss; (6) circumstellar chemistry; (7) thermal atmospheric models; (8) quasi-thermal models; (9) observations on the atmospheres of M dwarfs; and (1) theoretical work on M dwarfs.
    Keywords: ASTROPHYSICS
    Type: NASA-SP-492 , NAS 1.21:492 , LC-87-11340
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  • 15
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    Primordial nucleosynthesis with generic particles (1986)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: A revision of the standard model for Big Bang nucleosynthesis is discussed which allows for the presence of generic particle species. The primordial production of He-4 and D + He-3 is calculated as a function of the mass, spin degrees of freedom, and spin statistics of the generic particle for masses in the range 0.01-100 times the electron mass. The particular case of the Gelmini and Roncadelli majoron model for massive neutrinos is discussed.
    Keywords: ASTROPHYSICS
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  • 16
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    The evolution of massive stars (1982)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The hypotheses underlying theoretical studies of the evolution of massive model stars with and without mass loss are summarized. The evolutionary tracks followed by the models across theoretical Hertzsprung-Russell (HR) diagrams are compared with the observed distribution of B stars in an HR diagram. The pulsational properties of models of massive star are also described.
    Keywords: ASTROPHYSICS
    Type: B Stars With and Without Emission Lines, Parts 1 and 2; p 199-229
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  • 17
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    NASA sounding rockets to study eclipse (1980)
    In:  CASI
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    Publication Date: 2019-08-28
    Keywords: ASTROPHYSICS
    Type: NASA-NEWS-RELEASE-80-24 , P80-10023
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  • 18
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    Long Periodic Terms in the Solar System (1982)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The long period variations of the first eight planets in the solar system are studied. First, the Lagrangian solution is calculated and then the long period terms with fourth order eccentricities and inclinations are introduced into the perturbation function. A second approximation was made taking into account the short period terms' contribution, namely the perturbations of first order with respect to the masses. Special attention was paid to the determination of the integration constants. The relative importance of the different contributions is shown. It is useless, for example, to introduce the long period terms of fifth order if no account has been taken of the short period terms. Meanwhile, the terms that have been neglected would not introduce large changes in the integration constants. Even so, the calculation should be repeated with higher order short period terms and fifth order long periods.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76994 , NAS 1.15:76994
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  • 19
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    Observations of supernova SN1987a (1988)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Supernova SN1987a was discovered on February 23, 1987, in the Large Magellanic Cloud, a nearby galaxy that is visible only from the Southern Hemisphere. The NASA program for observations of SN1987a, which was developed rapidly after the discovery of the explosion, was designed to be implemented through a series of coordinated campaigns of gamma-ray, X-ray, ultraviolet, and infrared observations from spacecraft, rockets, balloons, aircraft and the ground. The author summarizes models for supernovae, recent results for SN1987a, and the NASA plans for further observations.
    Keywords: ASTROPHYSICS
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 35; 516-519
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  • 20
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    Significance of brown dwarfs (1986)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The significance of brown dwarfs for resolving some major problems in astronomy is discussed. The importance of brown dwarfs for models of star formation by fragmentation of molecular clouds and for obtaining independent measurements of the ages of stars in binary systems is addressed. The relationship of brown dwarfs to planets is considered.
    Keywords: ASTROPHYSICS
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  • 21
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    A 3-D computational model for solar wind/magnetosphere interactions - Prediction of polar flattening of Jupiter and Saturn magnetospheres (1987)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The development of a computational model for determining the solution of the gasdynamic portion of the gasdynamic convected magnetic field model for solar wind flow past three-dimensional magnetoionopauses of nonaxisymmetric shape is described. Results are presented for the shape of the bow wave and the flow properties in magnetosheaths of polar flattened magnetopauses representative of Jupiter and Saturn. Through a parametric study in which the amount of polar flattening is varied, a quantitative determination is obtained of the degree of flattening at both Jupiter and Saturn. These new three-dimensional results are shown to be in good agreement with observations, and account for most of the differences between the observations and the axisymmetric model results.
    Keywords: ASTROPHYSICS
    Type: AIAA PAPER 87-1411
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  • 22
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    Astroblemes on trapp rock: Structural features and differences from impact structures on other targets (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The paper briefly characterizes the two known terrestrial meteorite craters on trapp rock: (1) Lonar, India (diameter 1,8 km) and Logancha, USSR (diameter 20 km). The features these craters have in common are identified, and their differences from problems on other types of targets are indicated. The probable reasons for these differences are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-88484 , NAS 1.15:88484
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  • 23
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    Zhamanshin meteor crater (1987)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: A historical survey and geographic, geologic and geophysical characteristics, the results of many years of study of the Zhamanshin meteor crater in the Northern Aral region, are reported. From this data the likely initial configuration and cause of formation of the crater are reconstructed. Petrographic and mineralogical analyses are given of the brecciated and remelted rocks, of the zhamanshinites and irgizite tektites in particular. The impact melting, dispersion and quenching processes resulting in tektite formation are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-88531 , NAS 1.15:88531
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  • 24
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    Scattered light in the IUE spectra of Epsilon Aurigae (1986)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Recent infrared photometry indicates that the alleged disk of particulate matter surrounding the mysterious secondary object in the Epsilon Aur system is cold, around 500 K. IUE spectra, on the other hand, contain significant flux in excess of that expected from an F0 Ia star in the far UV, which if interpreted as a hot secondary star leads to a possible contradiction with the IR data. Other models of the UV excess have been proposed, including the idea that the bulk of the short-wavelength flux is light scattered into the SWP camera from longer wavelengths. With the recent availability of a detailed generalized IUE descattering algorithm it is possible to thoroughly investigate the scattered-light contribution to the short-wavelength continuum. It is found that the IUE spectra are indeed partially contaminated by scattered light, but that even after correction for this instrumental effect a significant time-dependent UV excess is still present.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 65; 1, Ju
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  • 25
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    Analytical electron microscopy of Mg-SiO smokes - A comparison with infrared and XRD studies (1986)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Analytical electron microscopy conducted for Mg-SiO smokes (experimentally obtained from samples previously characterized by IR spectroscopy) indicates that the microcrystallinity content of unannealed smokes increases with increased annealing for up to 30 hr. The growth of forsterite microcrystallites in the initially nonstoichiometric smokes may give rise to the contemporaneous growth of the SiO polymorph tridymite and MgO; after 4 hr of annealing, these react to form enstatite. It is suggested that XRD analysis and IR spectroscopy should be conducted in conjunction with detailed analytical electron microscopy for the detection of emerging crystallinity in vapor-phase condensates.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 66; 211-222
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  • 26
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    Meteoritic evidence that graphite is rare in the interstellar medium (1985)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Carbonaceous material from several distinct astrophysical environments that has been identified in primitive meteorites is discussed. Most of this material is not well crystallized graphite, but ranges from kerogenlike macromolecular organic matter to poorly graphitized carbon. Of the small fraction of the carbonaceous material which is graphite, most may have resulted from the graphitization of macromolecular precursors in the solar nebula. Since graphite is more stable than those precursors, preexisting interstellar graphite should have survived in meteorites to at least the same extent as did other forms of carbon. It is concluded from this dearth of graphite that graphitic carbon was not a major component of the interstellar dust at the time of the formation of the solar system.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 318; 166-168
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  • 27
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    Ultraviolet spectroscopy of meteoric debris: In situ calibration experiments from Earth orbit (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: It is proposed to carry out slitless spectroscopy at ultraviolet wavelengths from orbit of meteoric debris associated with comets. The Eta Aquarid, Orionid/Halley, and the Persied/1962 862 Swift-Tuttle showers would be principal targets. Low light level, ultraviolet video technique will be used during night side of the orbit in a wide field, earthward viewing mode. Data will be stored in compact video cassette recorders. The experiment may be configured as a GAS package or in the HITCHHIKER mode. The latter would allow flexible pointing capability beyond that offered by shuttle orientation of the GAS package, and doubling of the data record. The 1100 to 3200 A spectral region should show emissions of atomic, ionic, and molecular species of interest on cometary and solar system studies.
    Keywords: ASTROPHYSICS
    Type: NASA. Lyndon B. Johnson Space Center Space Station Planetology Experiments; 2 p
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  • 28
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    Report on opportunities and/or techniques for high-caliber experimental research (other) proposals for SSPEX (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Brief discriptions of the following 13 experiments are included: ultrahigh vacuum petrology facility; artificial comet free flyer; artificial comet (tethered); cosmic dust detector; cosmic dust collector; dust collection using tethered satellites; artificial magnetosphere; microgravity petrological studies; slitless ultraviolet spectrometer; orbital determination and capture experiment (ODACE); high velocity sputtering of amorphous silicates; particle release experiments; and calibration of gamma and X-ray remote sensingprobes.
    Keywords: ASTROPHYSICS
    Type: NASA. Lyndon B. Johnson Space Center Space Station Planetology Experiments (SSPEX); 5 p
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  • 29
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    Ultraviolet spectroscopy of meteoric debris of comets (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: It is proposed to carry out slitless spectroscopy at ultraviolet wavelengths from orbit of meteoric debris associated with comets. The Eta Aquarid and Orionid/Halley and the Perseid/1962 862 Swift-Tuttle showers would be principal targets. Low light level, ultraviolet video technique will be used during night side of the orbit in a wide field, earthward viewing mode. Data will be stored in compact video cassette recorders. The experiment may be configured as a GAS package or in the HITCHHIKER mode. The latter would allow flexible pointing capability beyond that offered by shuttle orientation of the GAS package, and doubling of the data record. The 1100 to 3200 A spectral region should show emissions of atomic, ionic, and molecular species of interest on cometary and solar system studies.
    Keywords: ASTROPHYSICS
    Type: Interrelationships among Circumstellar, Interstellar and Interplanetary Dust; 3 p
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  • 30
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    Meteorite craters (1986)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: The origin and formation of various types of craters, both on the Earth and on other planetary bodies, are discussed. Various models are utilized to depict various potential causes of the types and forms of meteorite craters in our solar system, and the geological structures are also discussed.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-78013 , NAS 1.15:78013
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  • 31
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    Observational studies of the symbiotic stars. III High-dispersion IUE and H-alpha observations of EG Andromedae (1985)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: High-dispersion IUE and optical spectra are presented for the symbiotic star EG Andromedae (HD 4174). Remarkable emission-line strength and profile variations are confirmed for the S IV, O IV, C IV, and He II ultraviolet lines as well as H-alpha. Accurate cross-correlation absorption-line velocities determined from Ti I, Ca I, and Fe I features convincingly demonstrate that EG And is a single-lined spectroscopic binary. The velocity curve suggests that the photometric ephemeris reported by Smith in 1980 should be revised by a redefinition of zero phase by about 0.08 of a period. The primary of the system may be similar to the central star of a planetary nebula embedded in a dense nebula with a mild stellar wind. The behavior of the emission lines is interpreted to indicate that the primary and its surrounding nebula suffer a partial eclipse by the cool giant secondary.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 295; 620-627
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  • 32
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    The geometric extent of C II (UV 0.01) emitting regions around luminous, late-type stars (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: A method is presented by which the geometric extent of the chromospheres around late-type stars can be estimated from measurements of the total emission-line flux and line ratios within the C II (UV 0.01) multiplet. Application of this technique to a sample of 15 late-type stars indicates a clear difference in the radial extent of the chromospheres around coronal and noncoronal stars. The former stars appear to have very thin chromospheres (of no more than 0.1 percent of the photospheric radius), while the latter stars have chromospheres extending, on average, out to 2.5 photospheric radii. This, in principle, provides information for understanding structural differences between late-type giant and supergiant stars with and without coronae, and could lead to an understanding of the mass-loss mechanisms involved.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 289; 676-680
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    Rotational modulation of chromospheric emission in cool giants and 'hybrid' stars (1985)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Archival data from the International Ultraviolet Explorer have been used to study temporal variations of the Mg II h and k emission lines in eight late-type giants. Evidence is presented that the variations are periodic in nature. It is argued that the periodicities can be interpreted in terms of rotation. It is found that the four fastest rotators in the sample are 'hybrid' stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 288; 310-328
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  • 34
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    Infrared emission from M31 (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Maps of M31 have been obtained at wavelengths of 12, 25, 60, and 100 microns. Emission is detected from the center and from a ring of 50 arcmin radius. The ring is that also seen in H I, in H II, and in radio continuum radiation. The spectrum of the central emission suggests a hotter dust temperature than in the ring. M31 is a weak infrared source, the radiation measured longward of 12 microns being only 3 percent of its total luminosity. The two closest companion galaxies, M32 and NGC 205, have also been detected.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 278; L59-L62
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    Infrared cirrus - New components of the extended infrared emission (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Extended sources of far-infrared emission superposed on the zodiacal and galactic backgrounds are found at high galactic latitudes and near the ecliptic plane. Clouds of interstellar dust at color temperatures as high as 35 K account for much of this complex structure, but the relationship to H I column density is not simple. Other features of the extended emission show the existence of warm structures within the solar system. Three bands of dust clouds at temperatures of 150-200 K appear within 10 deg on both sides of the ecliptic plane. Their ecliptic latitudes and derived distances suggest that they are associated with the main asteroid belt. A third component of the 100-micron cirrus, poorly correlated with H I, may represent cold material in the outer solar system or a new component of the interstellar medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 278; L19-L22
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    Observations of active chromosphere stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: It is pointed out that spectroscopic signatures of stellar chromospheric activity are readily observable. The present study is concerned with new photometric and spectroscopic observations of active-chromosphere RS CVn, BY Dra, and FK Com stars. Attention is given to the first results of a synoptic monitoring program of many active chromosphere stars. During the time from 1980 to 1982, photometric and spectroscopic observations of 10 known or suspected active-chromosphere objects were made. The results regarding the individual stars are discussed. Seven stars observed with the International Ultraviolet Explorer (IUE) are all spectroscopic binaries.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 691-703
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    The states of Cygnus X-1 (1983)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: HEAO 3 High Resolution Gamma-Ray Spectrometer observations of Cygnus X-1 in the 48-300 keV range, along with correlated 3-6 keV Ariel 5 data, have led to the identification of a new state for this object with low flux in both the soft and hard X-ray regions. This is followed by a slow increase in the hard X-ray flux to the normal low state of the source, characterized by a low intensity soft X-ray emission and a high intensity hard X-ray emission. The new 'superlow' state is interpreted in terms of the Compton model, where the X-ray emission arises from the scattering of low energy photons and one-billion K hot electrons. The superlow state may be seen as one extreme of a continuum of low state behavior, given that Compton cooling should begin to quench the hot electrons at higher soft X-ray fluxes, giving rise to the softer X-ray spectrum and to the anticorrelation in changes in the soft and hard X-ray fluxes.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 307-315
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  • 38
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    Redshifts of high-temperature emission lines in the far-ultraviolet spectra of late-type stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: High-dispersion IUE spectra of six late-type stars exhibit small but statistically significant differential redshifts of high-temperature emission lines, like Si IV and C IV, with respect to low-temperature lines like S I and O I. A well-exposed, small-aperture spectrum of the active chromosphere binary Capella (Alpha Aurigae A: G6 II+F9 III) establishes that the high-temperature lines are redshifted in an absolute sense with respect to the accurately determined photospheric velocity of the system at single-line phase 0.50. Several possible explanations for the stellar redshifts are discused, including a warm wind (100,000 K) in which aparent redshifts are produced in optically thick lines by an accelerating outfow, and the downflowing component of a vertical circulation system for which the up-leg portion of the flow is too cool, too hot, or too tenuous to be visible in Si IV and C IV. If the second scenario is true, the stellar redshifts may provide an important phenomenological link to the downflows observed in 100,000 K species over magnetic active regions in the sun.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 801-814
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  • 39
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    Inferences on the Thermodynamic Characteristics of a Star from the Observed Distinctive Radial Sequences of the Distinctive Atmospheric Regions Comprising that Stellar Atmosphere (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The implications of observational findings on atmospheric and subatmospheric taxonomy, diagnostics, and modeling are explored. The correlations between distinctive radial sequences in stellar atmospheres and the thermodynamic properties of the stars in which they appear are discussed.
    Keywords: ASTROPHYSICS
    Type: Stellar Atmospheric Struct. Patterns; p 333-349
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  • 40
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    Observed Distinctive Radial Sequences of the Distinctive Atmospheric Regions Comprising Stellar Atmospheres (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Gross distinctive radial sequences of stellar atmospheric regions are identified and characterized observationally and thermodynamically. Sequences which include quasi-thermal photospheres, ejected shell photospheres, and spherically pulsating photospheres are discussed.
    Keywords: ASTROPHYSICS
    Type: Stellar Atmospheric Struct. Patterns; p 323-331
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  • 41
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    Speculative-theoretical Modeling of the Atmosphere Enveloping a Hypothetical (closed, Thermal) Star (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The predictions of theoretical stellar atmospheric structural modeling and the theoretical picture of the local stellar environment as derived from the speculation that stars are (closed, thermal) thermodynamic systems, are summarized. The definition and representation of space- and state-fluxes is discussed and both classical (local thermodynamic equilibrium) and neoclassical (non-local thermodynamic equilibrium) thermal models are addressed.
    Keywords: ASTROPHYSICS
    Type: Stellar Atmospheric Struct. Patterns; p 19-113
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  • 42
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    Characteristics of Distinctive Regions Comprising Stellar Atmospheres (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Empirically identified atmospheric regions whose existence and properties generally have no classical-theoretical basis are discussed. The quasi-thermal photosphere, chromosphere, lower corona, upper corona, non-decelerated post corona, decelerated post corona, and the H sub alpha emission envelope are defined. The observational phenomena, thermodynamic mechanisms, and diagnostic aspects associated with each of the atmospheric layers are described.
    Keywords: ASTROPHYSICS
    Type: Stellar Atmospheric Struct. Patterns; p 279-322
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  • 43
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    Gamma Ray Astrophysics: New insight into the universe (1981)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Gamma ray observations of the solar system, the galaxy and extragalactic radiation are reported. Topics include: planets, comets, and asteroids; solar observations; interstellar medium and galactic structure; compact objects; cosmology; and diffuse radiation. The instrumentation used in gamma ray astronomy in covered along with techniques for the analysis of observational spectra.
    Keywords: ASTROPHYSICS
    Type: NASA-SP-453 , NAS 1.21:453 , LC-81-600116
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  • 44
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    The A-stars: Problems and perspectives. Monograph series on nonthermal phenomena in stellar atmospheres (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Normal A type stars, nonradiative heating in A type stars, magnetic Ap stars. The Am stars, the delta Scu stars, A supergiants, peculiar B type stars, and model atmospheres are addressed.
    Keywords: ASTROPHYSICS
    Type: NASA-SP-463 , NAS 1.21:463 , LC-83-061448
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  • 45
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    Physics of the central engine (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Physical processes which may be important in the central engines of AGNs are discussed. Black hole accretion models have been elaborated during the past few years, and provide a plausible framework for jet and spectrum formation. However, the specific mechanisms responsible for producing the observed continuum radiation remain uncertain. Consideration is given to nonthermal models for the IR continuum, constraints on thermal plasma, and the production of relativistic electrons.
    Keywords: ASTROPHYSICS
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  • 46
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    The peculiar planetary nebula in M22 (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The source discovered by the IRAS satellite near the center of the globular cluster M22, IRAS 18333-2357, has been studied using the IUE satellite and a ground-based optical telescope. The northern component of the close pair of stars is not a member of the cluster. The southern component is a hot star with T(eff) of about 50,000 K illuminating a small planetary nebula and is a member of M22. Both the planetary nebula and its central star are extremely hydrogen deficient. The luminosity of the central star is in good agreement with that expected on theoretical grounds and with the observed luminosity of the tip of the red giant branch.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 346; 803-807
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  • 47
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    Relativistic Gravitational Experiments in Space (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The results are summarized of a workshop on future gravitational physics space missions. The purpose of the workshop was to define generic technological requirements for such missions. NASA will use the results to direct its program of advanced technology development.
    Keywords: ASTROPHYSICS
    Type: NASA-CP-3046 , NAS 1.55:3046 , Jun 28, 1988 - Jun 30, 1988; Annapolis, MD; United States
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  • 48
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    FGK stars and T Tauri stars: Monograph series on nonthermal phenomena in stellar atmospheres (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The purpose of this book, FGK Stars and T Tauri Stars, like all other volumes of this series, is to exhibit and describe the best space data and ground based data currently available, and also to describe and critically evaluate the status of current theoretical models and physical mechanisms that have been proposed to interpret these data. The method for obtaining this book was to collect manuscripts from competent volunteer authors, and then to collate and edit these contributions to form a well structured book, which will be distributed to an international community of research astronomers by NASA and by the French CNRS.
    Keywords: ASTROPHYSICS
    Type: NASA-SP-502 , NAS 1.21:502 , LC-89-600317
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    The slow nova V1819 Cygni (Nova Cygni 1986) (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Spectrophotometric and spectropolarimetric observations of the slow nova Cygni 1986 were obtained with the 36-in Pine Bluff Observatory telescope beginning about one week after maximum and continuing for one-two years after maximum. An E(B-V) value of about 0.35 is found. In the months following maximum light, the Balmer decrement was extremely steep and variable with time. Departures from case B radiative transfer noted throughout most of the observational period are consistent with self-absorption of the Balmer lines due to high densities in parts of the nova shell. The results suggest that at 11 months after maximum the shell density was about 10 to the 7th/cu cm, dropping to about 10 to the 6th/cu cm two years after maximum.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 98; 297-310
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  • 50
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    Radial velocity study of four southern RS CVn candidates and related field stars (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Radial velocity variations are demonstrated for four southern RS CVn candidates: HD 39937, 101379, 155555, and 174429. The period of HD 155555 appears to have decreased by about one part in 100,000 over the past 18 yr. In addition, high-resolution observations of the Ca II H and K profiles and the Mg II 2800-A emission doublet are presented. These enhance the likelihood of these being RS CVn objects. Radial velocity data for 15 other late-type bright field stars are presented. Some of these were observed by Copernicus and may exhibit unusual chromospheres, while the rest lack radial velocity information as tabulated in the Bright Star Catalog. All velocity measures have been corrected to the IAU heliocentric system.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 85; July 198
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    New method for determining the distances to certain extragalactic radio sources (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The structural evolution of variable radio sources is examined in the Hedgehog model. It is shown that the time evolution of the angular separation of two components is described by the ellipse equation.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-76209 , PR-325
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    Space telescope searches for black holes in galactic nuclei (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The Hubble Space Telescope (HST) will allow astronomers to obtain luminosity profiles, rotation curves, and velocity dispersions at angular scales that are an order of magnitude superior to those obtained previously. This enhanced spatial resolution will greatly improve the sensitivity for detecting centrally condensed matter in nearby galactic nuclei including, possibly, black holes.
    Keywords: ASTROPHYSICS
    Type: Relativistic Gravitational Experiments in Space; p 110-113
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  • 53
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    Chromospheric dust formation, stellar masers and mass loss (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: A multistep scenario which describes a plausible mass loss mechanism associated with red giant and related stars is outlined. The process involves triggering a condensation instability in an extended chromosphere, leading to the formation of cool, dense clouds which are conducive to the formation of molecules and dust grains. Once formed, the dust can be driven away from the star by radiation pressure. Consistency with various observed phenomena is discussed.
    Keywords: ASTROPHYSICS
    Type: Interrelationships among Circumstellar, Interstellar and Interplanetary Dust; 5 p
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    IUE and IRAS observations of luminous M stars with varying gas-to dust ratios (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Circumstellar gas and dust surrounding M giants and supergiants show luminous M stars to split into two distinct classes. Stars with a high gas to dust ratio all show chromospheric Ca II, H, and K emission. Stars with a high dust to gas ratio do not show chromospheric Ca II emission but are the only ones to show Balmer emission indicative of atmospheric shocks and are also the only ones to show maser emission. In order to determine whether all chromospheric indicators disappear in high dust to gas ratio stars, a survey of stars in both these classes was conducted with the IUE satellite. Long wavelength infrared fluxes for the program stars were obtained from the IRAS point source catalog. There is no obvious difference in the long wavelength observations between the two groups of stars. The long wavelength excess tends to follow the 10 micron excess and not the dust to gas ratio.
    Keywords: ASTROPHYSICS
    Type: Interrelationships among Circumstellar, Interstellar and Interplanetary Dust; 1 p
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  • 55
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    Anharmonicity and the interstellar polycyclic aromatic hydrocarbon infrared emission spectrum (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: The hypothesis that interstellar infrared emission originates from vibrationally excited polycyclic aromatic hydrocarbons (PAHs) requires that emission can arise from all vibrational levels that are energetically accessible. Due to anharmonicity, the emission from the upper vibrational levels is shifted to longer wavelengths from that of the v = 1-0 transition. It is shown that structure in the 3-micron region is readily and quantitatively explained by emission from upper vibrational levels of excited PAHs that contain a maximum of 20-30 carbon atoms. The asymmetrical broadening of the 11.3-micron emission band may also be due to anharmonicity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 315; L61-L65
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  • 56
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    Chromospheric dust formation, stellar masers and mass loss (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: A multistep scenario which describes a plausible mass loss mechanism associated with red giant and related stars is outlined. The process involves triggering a condensation instability in an extended chromosphere, leading to the formation of cool, dense clouds which are conducive to the formation of molecules and dust grains. Once formed, the dust can be driven away from the star by radiation pressure. Consistency with various observed phenomena is discussed.
    Keywords: ASTROPHYSICS
    Type: Irish Astronomical Journal (ISSN 0021-1052); 17; 336-342
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  • 57
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    Homogeneous cosmological models and new inflation (1986)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The promise of the inflationary-universe scenario is to free the present state of the universe from extreme dependence upon initial data. Paradoxically, inflation is usually analyzed in the context of the homogeneous and isotropic Robertson-Walker cosmological models. It is shown that all but a small subset of the homogeneous models undergo inflation. Any initial anisotropy is so strongly damped that if sufficient inflation occurs to solve the flatness and horizon problems, the universe today would still be very isotropic.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 57; 2237-224
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  • 58
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    N-point correlations for biased galaxy formation (1986)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: A general series expansion of arbitrary accuracy is given for the correlation function of the 'biased' regions of galaxy formation in terms of the mass autocorrelations. It is shown how to calculate the N-point correlations to arbitrary accuracy, and the validity of the various approximations is discussed. The asymptotic values of the N-point correlation functions at their highest point at zero spatial separation are given, and the scaling of these values is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 305; L5-L9
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    Changes in the ultraviolet spectrum of EG Andromedae (1984)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Ultraviolet observations of EG Andromedae, a symbiotic star, are reported which clearly show pronounced eclipse-like effects on the high-temperature far-UV continuum. Continuum and emission-line variations with phase are reported and related to synoptic hydrogen alpha data. System parameters are characterized.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 281; L75-L77
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    Observations of two peculiar emission objects in the Large Magellanic Cloud (1983)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Ultraviolet and visual wavelength spectra were obtained of two peculiar emission objects, Henize S63 and Sanduleak's star in the Large Magellanic Cloud. Previously not observed in the near- or far-ultraviolet, both objects exhibit strong permitted and semiforbidden line emissions. Estimates based on the absolute continuum flux of the hot companion star in Hen S63 indicate that it rivals the luminosity of the carbon star primary. The emission-line profile structure in both objects does not suggest Wolf-Rayet type emission. Carbon in Sanduleak's star (LMC anonymous) is conspicuously absent, while N V, semiforbidden N IV, and semiforbidden N III dominate the UV emission-line spectrum. Nitrogen is overabundant with respect to carbon and oxygen in both objects. The large overabundance of nitrogen in Sanduleak's star suggests evidence for CNO processes material similar to that seen in Nu Car.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 584-591
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    Evidence for a warm wind from the red star in symbiotic binaries (1983)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: A systematic redshift of the high ionization resonance emission lines with respect to the intercombination lines is found from an examination of the ultraviolet spectra of symbiotic stars obtained with IUE. After consideration of other possibilities, this is most probably explained by photon scattering in an expanding envelope optically thick to the resonance lines. Line formation in a wind, or at the base of a wind is therefore suggested. Reasons are also given indicating line formation of the most ionized species in a region with an electron temperature of the order of 100,000 K, probably around the cool star. The behavior of the emission line width with ionization energy seems to support this model. The cool components of symbiotic stars appear to differ from normal red giants, which do not have winds of this temperature. An explanation in terms of a higher rotation velocity due to the binary nature of these stars is suggested.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 126; 2, Oc
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  • 62
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    Stellar atmospheric structural patterns (1983)
    In:  CASI
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    Publication Date: 2019-08-27
    Description: The thermodynamics of stellar atmospheres is discussed. Particular attention is given to the relation between theoretical modeling and empirical evidence. The characteristics of distinctive atmospheric regions and their radical structures are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA-SP-471 , NAS 1.21:471 , LC-83-20242
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    Empirical-theoretical Survey of the Variety of Peculiarities and Anomalies in the Atmospheres Enveloping Actual Stars (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Phenomena observed in actual stellar atmospheres which contradict the speculative, standard thermal atmospheric model are discussed. Examples of stellar variability, emission line peculiarity, symbiotic stars and phenomena, extended atmosphere stars, superionization, and superthermic velocity are examined.
    Keywords: ASTROPHYSICS
    Type: Stellar Atmospheric Struct. Patterns; p 115-264
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    The narrow ultraviolet emission lines of the red dwarf Au Microscopii (dM1.6e) (1983)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: It is pointed out that the red dwarfs are the smallest, coolest, faintest, least massive, but most common of normal main-sequence stars. The dMe (H-alpha emission) subclass of the red dwarfs exhibits the largest median soft X-ray to bolometric luminosity ratio of any group of late-type stars. In connection with the present investigation, attention is given to the first high-dispersion spectra of the chromospheric (6000 K) and higher temperature (up to 100,000 K) emissions of a dMe star, AU Microscopii in the far-ultraviolet (1150-2000 A) and middle-ultraviolet (2000-3000 A) bands accessible to the International Ultraviolet Explorer (IUE). AU Mic is one of the most luminous of lower main-sequence stars in C IV and soft X-ray emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 270; July 1
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    International Ultraviolet Explorer observations of amorphous hot galaxies (1984)
    In:  CASI
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    Publication Date: 2019-08-14
    Description: In order to better understand the nature of star formation processes in amorphous galaxies, short wavelength International Ultraviolet Explorer (IUE) spectra of galaxies NGC 1705 and NGC 1800 were obtained. The IUE data for NGC 1705 were of excellent quality while the low signal-to-noise NGC 1800 observation was useful only as a rough guide to the ultraviolet energy distribution. It was found that NGC 1705 contains a normal mix of OB stars, which is consistent with the nearly constant recent star formation rate inferred from new optical data. The NGC 1800 is likely to have similar properties, and blue galaxies with amorphous structures thus do not show evidence for anomalies in stellar mass distributions. The UV spectra of amorphous galaxies and a variety of other hot extragalactic stellar systems have similar characteristics, which suggests OB stellar populations often are homogeneous in their properties.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-174354 , NAS 1.26:174354 , IAP-84-22
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  • 66
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    The cosmos today and tomorrow (1980)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The book ""Tested on Oneself'' is summarized and reviewed. Topics in the field of space flight and aerospace medicine are addressed.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-75736
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  • 67
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    High resolution observations of magnesium II 2800 A in Alpha Centauri A - The density of interstellar magnesium II and the stellar chromospheric profiles (1982)
    In:  Other Sources
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    Publication Date: 2019-08-13
    Description: The profiles are virtually identical with the solar profiles except for the presence of an absorption feature near line center in the h and k lines of Alpha Centauri A. It is found that this absorption feature can be explained by interstellar absorption of Mg II along the line of sight. The average density of Mg II is found to be 2.75 plus or minus 0.7 x 10 to the -7th/cu cm, in good agreement with the previously determined values in the solar vicinity in the direction of Alpha CMa and Alpha Lyr.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 252
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  • 68
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    Mercury in a thin layer in HgMn stars - A test of a diffusion model (1980)
    In:  Other Sources
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    Publication Date: 2019-08-13
    Description: Lines of the first three states of ionization of mercury have been observed in Mu Leporis and Chi Lupi using the Copernicus satellite. Lines of Hg II and Hg III have been observed in Alpha Andromedae. There appears to be an absorption feature at every wavelength where there is expected to be a mercury line. The presence of all three states of ionization is likely in Mu Lep and Chi Lup. The relative equivalent widths of the lines of the various states of ionization do not depend on the effective temperature of the stars, in contradiction to what is expected if mercury were uniformly distributed in the atmosphere. It is, however, expected if mercury has been concentrated, by diffusion, in a thin layer, where the radiative forces just equal the gravitational forces on mercury. That mercury should be so concentrated is also required by the explanation of the mercury isotope anomaly proposed by Michaud, Reeves, and Charland.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 239
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  • 69
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    Thermal instabilities in diffuse molecular clouds - Formation of molecular cloud cores (1987)
    In:  Other Sources
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    Publication Date: 2019-08-13
    Description: The stability of diffuse clouds to thermal instabilities is examined using the semiempirical cooling function derived by Tarafdar et al. (1985) for these clouds. It is found that diffuse clouds which obey such a cooling function are susceptible to thermal instability at densities n of less than about 70-80/cu cm. The growth rate for instability is large and the mass contained in unstable regions ranges from about 0.001 to 1 solar mass. It is suggested that such instabilities may trigger formation of molecular cloud cores of the type found in low-mass molecular clouds (e.g., TMC-2). Criteria for thermal instability in self-gravitating systems are also derived.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters (ISSN 0004-6388); 25; 4 19; 235-245
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  • 70
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    Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter (1986)
    In:  Other Sources
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    Publication Date: 2019-08-13
    Description: The IUE spectrophotometry of Comet P/Giacobini-Zinner was acquired in support of the International Cometary Explorer (ICE) mission. The abundances (or upper limits) of UV-active species were calculated. During the ICE encounter the H2O production rate was 3 times 10 to the 28th power/sec, + or - 50%, consistent with values derived from the ICE experiments. Comparison of the abundance of CO2(+) ions with the total electron density measured by the plasma electron experiment on ICE indicates a deficiency of ions relative to electrons indicating a population of ions not detected by remote sensing. The absence of detectable Mg(+) rules out this species as a possible ion of M/Q = 24 detected by the Ion Composition Instrument, part of the ICE complement of instruments.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE; p 35-38
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  • 71
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    Models for application of radiation boundary condition for MHD waves in collapse calculations (1986)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The problem of reflection of magnetohydrodynamic (MHD) waves at the boundary of a numerical grid has to be resolved in order to obtain reliable results for the end state of the (isothermal) collapse of a rotating, magnetic protostellar cloud. Since the goal of investigating magnetic braking in collapse simulations is to see if the transport of angular momentum via alfven waves is large enough to solve the angular momentum problem an approximation that artificially suppresses large amplitudes in the MHD waves can be self-defeating. For this reason, four alternate methods of handling reflected waves where no assumptions are made regarding the amplitudes of the waves were investigated. In order to study this problem (of reflection) without interference from other effects these methods were tried on two simpler cases. The four methods are discussed.
    Keywords: ASTROPHYSICS
    Type: Summer School on Interstellar Processes: Abstracts of Contributed Papers; p 171-172
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  • 72
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    Observations of Local Interstellar Mg I and Mg II (1984)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Copernicus and IUE observations of 5 stars within 50 pc of the Sun were combined to study the ionization of magnesium in the local interstellar medium (LISM). The high resolution Copernicus spectrometer was used to detect interstellar MG I 2852 in the spectra of alpha Gru, alpha Eri, and alpha Lyr, while placing upper limits on Mg I in the spectra of alpha CMa and alpha PsA. Observations of Mg II 2795, 2802 for these stars were also obtained with IUE and Copernicus. The column densities of Mg I and Mg II are used to place constraints on the temperature of the LISM.
    Keywords: ASTROPHYSICS
    Type: Local Interstellar Medium, No. 81; p 64-66
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  • 73
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    C II forbidden line emission from spiral galaxies (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Measurements of 158-micron forbidden emission taken from a sample of 13 gas-rich galaxies are analyzed. The new data are combined with the previous sample of six infrared-bright galaxies. The 158-micron line emission line is bright in all of the galaxies detected, amounting to between 0.1 and 0.2 percent of the total nuclear far-infrared luminosity, and is therefore one of the primary gas coolants in these regions. A close association between 158-micron line emission and CO line emission is noted, with the integrated 158-micron/CO line intensity ratio being substantially less in galaxies than in Galactic star-formation regions. However, for the starburst galaxies the integrated line intensity ratio is the same as that for star-formation regions in the Galaxy.
    Keywords: ASTROPHYSICS
    Type: Physics and Chemistry of Interstellar Molecular Clouds - MM and Sub-MM Observations in Astrophysics; Sept. 22-25, 1988; Zermatt; Switzerland
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  • 74
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    On the far-IR and sub-mm spectra of spiral galaxies (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Photometric measurements of three Virgo cluster spirals (NGC4254, NGC4501, and NGC4654) at 160-microns (far-infrared) and 360-microns (submillimeter) wavelengths are compared with theoretical models and observations at other wavelengths. It is shown that the data at the observed wavelengths do not fit any of interstellar dust grain models very well; four possibilities are given in order to explain discrepancies: the observed wavelength points are incorrect; previously observed data is incorrect; both data are incorrect; and the premise of the analysis is incorrect - a composite far-infrared spectrum of normal spiral galaxies is meaningless because they vary considerably in their far-infrared properties. It is also noted that the observed data are inconsistent with models having large cold grains.
    Keywords: ASTROPHYSICS
    Type: Physics and Chemistry of Interstellar Molecular Clouds - MM and Sub-MM Observations in Astrophysics; Sept. 22-25, 1988; Zermatt; Switzerland
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  • 75
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    Observations of H2(O-18) at 547 GHz with the Kuiper Airborne Observatory (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The 1(10)-1(01) transition of H2(O-18) has been searched for in several sources without positive detection. However, in NGC 2264 and NGC 7538, possible emission features are suspected. Implications of these feataures, if confirmed, are discussed. The best upper limit obtained in Orion (0.9 K) indicates that in that cloud, the water abundance should not be more than 1 percent that of CO.
    Keywords: ASTROPHYSICS
    Type: Physics and Chemistry of Interstellar Molecular Clouds - MM and Sub-MM Observations in Astrophysics; Sept. 22-25, 1988; Zermatt; Switzerland
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  • 76
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    Oxygen-rich mass loss from carbon-rich stars - Some implications (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The degree of dust-to-gas coupling in the atmospheres of red giant stars is evaluated, and nonzero drift velocities are found. Chemical fractionation of the stellar atmosphere on an evolutionary time scale is implied.
    Keywords: ASTROPHYSICS
    Type: AIP Conference on Cosmic Abundances of Matter; Sept. 7-9, 1988; Minneapolis, MN; United States
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  • 77
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    Propagation of cosmic-rays nuclei in the interstellar medium - The importance of energy losses revisited (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Keywords: ASTROPHYSICS
    Type: AIP Conference on Cosmic Abundances of Matter; Sept. 7-9, 1988; Minneapolis, MN; United States
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  • 78
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    Abundances of the elements in the intergalactic medium (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A summary of the X-ray and optical spectroscopic data on emission lines from elements in clusters of galaxies is presented. The best data exists for Fe. For the about 30 well-observed clusters, the mean Fe abundance is about 0.4 solar, but there appears to be a real variation of at least a factor of 2. X-ray emission lines from O, Mg, Si and S have been detected, and their abundances are within a factor of a few of solar. Analysis of optical emission lines from cooling gas due to O, N, and S also indicates abundances not too far from solar values. The implications of the presence of heavy elements in the intergalactic medium of clusters for the evolution of the chemical abundances of galaxies are discussed.
    Keywords: ASTROPHYSICS
    Type: AIP Conference on Cosmic Abundances of Matter; Sept. 7-9, 1988; Minneapolis, MN; United States
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  • 79
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    Solar-system abundances of the elements - A new table (1989)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: This paper presents an abridged version of a new abundance compilation (Anders and Grevesse, 1988), representing an update of Anders and Ebihara (1982) and Grevesse (1984). It includes revised meteoritic abundances as well as photospheric and coronal abundances, based on literature through mid-1988.
    Keywords: ASTROPHYSICS
    Type: AIP Conference on Cosmic Abundances of Matter; Sept. 7-9, 1988; Minneapolis, MN; United States
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  • 80
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    The nature of comets (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The large-scale structure, dynamics, and chemical composition of comets are examined on the basis of preliminary ground-based and space-probe data from the Halley return of 1986. Diagrams, graphs, photographs, and false-color images are provided, and data on Comet Giacobini-Zinner are included for comparison. Features noted include solar-wind interaction with magnetic-field draping around the head region, dramatic disconnection events, an irregularly shaped monolithic primarily water-ice nucleus and a dark surface, and dust with chemical composition like that of (H, C, N, O)-enriched carbonaceous chondrites.
    Keywords: ASTROPHYSICS
    Type: Diffuse matter in the solar system: Comet Halley and other studies; May 21, 22, 1986; London
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  • 81
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    An X-ray survey of supernova remnants in the Large Magellanic Cloud (1982)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Preliminary observation results for SNRs in the LMC are presented, and the current status of programs investigating these observational data is assessed. High Resolution Imager maps indicate that the remnant diameters used in early rate calculations were systematically underestimated. A preliminary SN rate of 1/110-350 years is derived upon reconsideration of these data. It is noted that most of the remnants detected in the LMC have very soft spectra, and would be undetectable as X-ray sources at distances of 5-10 kpc in the galactic plane.
    Keywords: ASTROPHYSICS
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  • 82
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    An optimist's guide to supernovae (1982)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: There are some hints that a satisfactory agreement between observations and models is developing in several areas of supernova research. The light curves and spectra of Type I supernovae look so much like the models that they may well have their origin in the synthesis of Ni-56 in the explosion of a compact star. Type II supernovae are found where massive stars form, have light curves that correspond to 10 to the 51st ergs suddenly deposited inside a red supergiant, and may in fact be the explosions of massive stars. Some young supernova remnants, such as Cas A, show abundance patterns that bear a striking resemblance to those seen deep inside models of massive stars on the verge of destruction. Observations of old supernova remnants provide energy estimate of 10 to the 51st ergs - just the amount needed for the models of the outbursts.
    Keywords: ASTROPHYSICS
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  • 83
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    Supernovae and the formation of galaxies (1982)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Attention is given to the cumulative effect of many SNs in a galaxy, especially a young galaxy, as well as the effect of the blast wave resulting from the combination of all individual SNs on the intergalactic medium (IGM). It is suggested that the IGM can be shock-heated by this process, so that in the late stages of an individual expanding galaxy's shock a shell may form whose mass is many times greater than that of the seed galaxy. If this shell fragments, due to gravitational instability, it will give rise to a new generation of galaxies. SN explosions may thereby provide a hydrodynamic amplifier of some significance in the process of galaxy formation.
    Keywords: ASTROPHYSICS
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  • 84
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    X-ray spectroscopy and imagery of supernova remnants with the Einstein Observatory (1982)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The two complementary spectroscopic instruments of the Einsten Observatory make possible X-ray spectroscopy of SNRs with considerably increased sensitivity and spectral resolution. The Solid State Spectrometer is a cryogenically cooled detector with 160 eV resolution, which suffices not only for the separation of lines due to different elements, but also the resolution of H-like, He-like and neutral lines from the same element for Si and above. The Focal Plane Crystal Spectrometer uses Bragg crystals to achieve excellent spectral resolution, but at the expense of sensitivity. Both instruments operate over most of the 0.2-4 keV energy band of the Einstein telescope, and are able to detect most of the important X-ray lines except the K lines of Fe and Ni.
    Keywords: ASTROPHYSICS
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  • 85
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    Supernovae and the origin of the solar system (1982)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A review is presented of the astrophysical reasoning that links supernovae to the origin of the solar system. Topics examined concerning the supernova connections include the abundances of the nuclides at the time the solar system formed, the collapse of a solar cloud by supernova triggering, the origins of isotopic anomalies in solar system samples, and the sputtering of interstellar dust with the attendant chemical and isotopic evolution of the interstellar medium. The controversies surrounding each of these topics are critically examined, focusing on the issues arising from the discovery of the isotopic anomalies in meteorites.
    Keywords: ASTROPHYSICS
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  • 86
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    The origin of the Crab Nebula and electron capture supernova of 8-10 solar-mass stars (1982)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: (Previously announced in STAR as N81-32097)
    Keywords: ASTROPHYSICS
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  • 87
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    A review of cometary sciences (1987)
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    Publication Date: 2019-07-27
    Description: This paper presents an elementary description of comets and their nature. It deals with the contribution from comets to the solid particles that produce the Zodiacal Light and discusses the possibility that some comets in short-period orbits may degenerate into asteroids. The evidence suggests that this may well have happened for the Trojan and other of the outer asteroids but that the near-earth asteroids and the meteorites are largely not cometary in origin. The last section of the paper deals with the possible nature of comets and their origin such that some might become superficially indistinguishable from asteroids. Space missions are clearly needed, to answer some of these basic questions.
    Keywords: ASTROPHYSICS
    Type: Diffuse matter in the solar system: Comet Halley and other studies; May 21, 22, 1986; London
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  • 88
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    Search for molecules in Comet Halley at millimeter wavelengths (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Data collected with the Five College Radio Astronomy Observatory 13.7-m radio telescope are used to search for the possible CN parent molecules HNC, HC3N, and CH3CN in Comet Halley at millimeter wavelengths. Maximum relative abundances for HNC/HCN of 0.3, for HC3N/HCN of 0.4, and for CH3CN/HCN of 0.8 are obtained, showing that these three molecules are not a major source of the CN radical observed in optical and UV spectroscopy. Upper limits to the beam averaged column densities and production rates of these molecules are determined (in addition to an upper limit for the beam averaged column density for the formyl ion of less than 10 to the 11th/sq cm), providing important constraints for chemical models of the coma.
    Keywords: ASTROPHYSICS
    Type: Cometary radio astronomy; Sept. 24-26, 1986; Green Bank, WV; United States
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  • 89
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    Cometary plasma - A review (1987)
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    Publication Date: 2019-07-27
    Description: Results of spacecraft probing of Comet Halley and Comet Giacobini-Zinner are used to investigate cometary plasma processes and large-scale structure. Examples of tail phenomena are discussed, with emphasis on the observed disconnection events (DEs). The sector boundary/magnetic reconnection model for DEs of Niedner and Brandt, (1978) is shown to be consistent with the times of known DEs in Comet Halley as well as the magnetic polarity data available from interplanetary and near-earth satellites, and from solar data. Results of the present review have application to understanding of the solar-wind/comet interaction during the 1985-1986 apparition of Comet Halley.
    Keywords: ASTROPHYSICS
    Type: Cometary radio astronomy; Sept. 24-26, 1986; Green Bank, WV; United States
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  • 90
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    Observations of HCN in Comet Halley (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Observations of the HCN J = 1-0 rotational transition at 3.4 mm wavelength in comet P/Halley are discussed. The data were obtained during a total of 56 individual observing sessions between Nov. 18, 1985 and May 11, 1986, and represent the first time that a cometary parent molecule has been so extensively monitored. The HCN production rate is well correlated with the total visual magnitude of the comet, indicating that HCN follows the overall gas production. There is also evidence of time variability and variations in the HCN hyperfine ratios from their LTE values. Spectra obtained by binning the HCN data with heliocentric distance show that the HCN line width, and thus the parent outflow velocity, increases with decreasing heliocentric distance.
    Keywords: ASTROPHYSICS
    Type: Cometary radio astronomy; Sept. 24-26, 1986; Green Bank, WV; United States
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  • 91
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    Near-nucleus optical observations of P/Halley (1987)
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    Publication Date: 2019-07-27
    Description: The Near-Nucleus Studies Net of the International Halley Watch has obtained an extensive series of high resolution optical images of P/Halley during its most active phases in 1985-86 which may be useful in interpreting radio observations of Comet Halley. They often show coma structure resulting from anisotropic emission of dust and gas from the inhomogeneous nucleus. Images were obtained in broadband spectral regions to study dust coma morphology, and in medium to narrow spectral bands to isolate the principal emissions of CN, C3, C2, CO+ and H2O+. The goals and methods of near-nucleus studies are discussed and recent studies of 1910 images are briefly reviewed. The role of dust jets and cometary activity in P/Halley is discussed and several examples of anisotropic emission of dust during the current apparition are shown.
    Keywords: ASTROPHYSICS
    Type: Cometary radio astronomy; Sept. 24-26, 1986; Green Bank, WV; United States
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  • 92
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    Experimental constraints on heating and cooling rates of refractory inclusions in the early solar system (1987)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: The refractory inclusions in carbonaceous chondrites were the subject of considerable interest since their discovery. These inclusions contain minerals that are predicted to be some of the earliest condensates from the solar nebula, and contain a plethora of isotopic anomalies of unknown origin. Of particular interest are those coarse-grained inclusions that contain refractory metal particles (Fe, Ni, Pt, Ru, Os Ir). Experimental studies of these inclusions in terrestrial laboratories are, however, complicated because the dense particles tend to settle out of a molten or partially molten silicate material. Heating experiments in the Space Station technology and microgravity in order to observe the effects of metal nuggets (which may act as heterogeneous nucleation sites) on nucleation rates in silicate systems and to measure simultaneously the relative volatilization rate of siderophile and lithophile species. Neither experiment is possible in the terrestrial environment.
    Keywords: ASTROPHYSICS
    Type: NASA, Lyndon B. Johnson Space Center, Experiments in Planetary and Related Sciences and the Space Station; 1 p
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  • 93
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    A magnetospheric simulation at the Space Station (1987)
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    Publication Date: 2019-07-17
    Description: It is proposed that a strong magnet (terrella) be flown at or near the Space Station to create an artificial magnetosphere in a laboratory setting. The relative flow of the ionosphere past the terrella will constitute a plasma wind that will interact with the magnetic field of the terrella to produce a localized magnetosphere. This object could then be extensively studied using diagnostic probes attached to the Space Station or with free flyers. The space and storage requirements would be minimal, since the experiment would be conducted outside the Space Station. The total equipment would consist of several terrella (with varying surface conductivities), approximately 3 small magnetometer/plasma diagnostic packages, and several gas canisters for upstream seeding. Power requirements would be approximately 60 watts. Several track mounted tethers, each approximately or 200 m long in length, with track parallel to the orbital motion and 100 m long, are also needed. Astronaut time needed would be minimal in the tethered configuration (approximately 4 man hours/week). A free flying configuration, while not needing the tether track, would require much more human interaction.
    Keywords: ASTROPHYSICS
    Type: NASA, Lyndon B. Johnson Space Center, Experiments in Planetary and Related Sciences and the Space Station; 1 p
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    New techniques for the detection and capture of micrometeoroids (1987)
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    Details
    Publication Date: 2019-07-17
    Description: In order to understand the origin and distribution of the biogenic elements and their compounds in the solar system, it will be necessary to study materials from many classes of objects. Chemical, elemental, and isotopic measurements of returned samples of comets, asteroids, and possibly extra-solar system dust clouds would provide information on a particularly important class: primitive objects. Extraterrestrial micron-sized particles in the vicinity of Earth are one source of such materials that might otherwise be inaccessible. The Space Station appears to be an eminently suitable platform from which to collect and detect these various particles. The primary challenge, however, is to collect intact, uncontaminated particles which will be encountered at tens of kilometers per seconds. A concept for a micrometeoroid detector that could be deployed from the Space Station was developed which uses a large area detector plate implanted with acoustic transducers. When an impact event occurs, the resulting signal is subjected to spectral analysis providing positive detection, momentum information, and angle of incidence. The primary advantage of this detector is the large area which increases the probability of measuring events. A concept of a nondestuctive micrometeoroid collector for use from a Space Station was also developed. The collector utilizes input port charging of the incoming particle followed by staged high voltage deceleration for nondestructive capture. Low velocity particles (local contamination) would be rejected due to insufficient energy and only uncontaminated micrometeoroids would be collected.
    Keywords: ASTROPHYSICS
    Type: NASA, Lyndon B. Johnson Space Center, Experiments in Planetary and Related Sciences and the Space Station; 1 p
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    Collisional dynamics of perturbed particle disks in the solar system (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Theoretical and computational studies were carried out on galactic and planetary disks. With the goal of addressing important open questions centered on galactic structure, the cloudy interstellar medium, giant molecular clouds, and star formation in galactic disks and the collisional dynamics of perturbed particulate matter in planetary disks, focus was largely on the self-gravitational effects, dissipative effects, and collisional dynamics of cloud-particle disks. N-body, 'cloud-particle' computational algorithms were developed for the purpose of isolating the role of gaseous self gravity from the roles of other dominant physical mechanisms and dynamical processes, e.g. the collisional dynamics and dissipative processes. The efforts focused largely on galactic disks show that observational constraints provide stringent tests of the numerical simulation techniques developed. Self gravitational effects of the galactic interstellar medium's gas clouds are included by means of Fourier Transform technique.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-193584 , NAS 1.26:193584
    Format: application/pdf
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  • 96
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    Analysis of interstellar fragmentation structure based on IRAS images (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The goal of this project was to develop new tools for the analysis of the structure of densely sampled maps of interstellar star-forming regions. A particular emphasis was on the recognition and characterization of nested hierarchical structure and fractal irregularity, and their relation to the level of star formation activity. The panoramic IRAS images provided data with the required range in spatial scale, greater than a factor of 100, and in column density, greater than a factor of 50. In order to construct a densely sampled column density map of a cloud complex which is both self-gravitating and not (yet?) stirred up much by star formation, a column density image of the Taurus region has been constructed from IRAS data. The primary drawback to using the IRAS data for this purpose is that it contains no velocity information, and the possible importance of projection effects must be kept in mind.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-193518 , NAS 1.26:193518
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  • 97
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    X-rays from Wolf-Rayet stars observed by the Einstein Observatory (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Preliminary results of three X-ray surveys are presented. Out of a sample of 20 stars, X-rays were detected from four Wolf-Rayet stars and two O8f(+) stars. The detected stars have about the same mean value as O stars for the X-ray to total luminosity ratio, L(x)/L = 10 to the -7th, but exhibit a much larger variation about the mean. The spectral energy distributions are also found to be like that of O stars in that they do not exhibit large attenuation of X-rays softer than 1 keV. This indicates that for both the O stars and WR stars much of the X-ray emission is coming from hot wisps or shocks in the outer regions of the winds and not from a thin source at the base of the wind. The general spectral shape and flux level place severe restrictions on models that attribute the lack of hydrogen emission lines to extremely high temperatures of the gas in the wind.
    Keywords: ASTROPHYSICS
    Type: In: Wolf-Rayet stars: Observations, physics, evolution; Sep 18, 1981 - Sep 22, 1981; Cozumel; Mexico
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  • 98
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    Chemical composition of Wolf-Rayet stars - Abundant evidence for anomalies (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Keywords: ASTROPHYSICS
    Type: In: Wolf-Rayet stars: Observations, physics, evolution; Sep 18, 1981 - Sep 22, 1981; Cozumel; Mexico
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  • 99
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    Hot mantles, moderate photospheres for Wolf-Rayet stars (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The amount of continuous energy from Wolf-Rayet stars and the shape of the continuous spectrum from the ultraviolet to the near infrared correspond to effective temperatures in the range 25,000 to 30,000 K. The value of log g is of the order of 4.0 + or - 0.5. Thus the photospheres of Wolf-Rayet stars correspond to those of moderately hot stars. The line spectra of Wolf-Rayet stars, however, indicate that electron temperatures greater than 30,000 K occur in the outer atmospheres or mantles of these stars. Here outflow is important.
    Keywords: ASTROPHYSICS
    Type: In: Wolf-Rayet stars: Observations, physics, evolution; Sep 18, 1981 - Sep 22, 1981; Cozumel; Mexico
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  • 100
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    Subluminous Wolf-Rayet stars - Observations (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Even though the loss of the outer, H-rich envelope may be a necessary condition for forming WR stars, it is clearly not a sufficient one. This is because the majority of planetary nuclei do not have a WR-type spectrum. The question why some central stars are WR stars while others are, say, O stars is addressed here. The question is approached by ascertaining how the properties of WR-type central stars differ from those of O-type stars. The study therefore begins with the classification and calibration of WR spectra. It is found that whereas the WR phenomenon may occur in stars of any mass, it is limited to stars that have been stripped (or mixed) down to their cores. The fact of prior envelope loss, however, is not sufficient to predict which stars will develop WR characteristics. Instead, a comprehensive description of envelope loss, including a detailed accounting of interior conditions and processes at the core envelope interface, will be required to explain the onset of WR characteristics.
    Keywords: ASTROPHYSICS
    Type: In: Wolf-Rayet stars: Observations, physics, evolution; Sep 18, 1981 - Sep 22, 1981; Cozumel; Mexico
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