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  • Organic Chemistry  (714)
  • ASTROPHYSICS  (578)
  • Humans
  • 1980-1984  (1,608)
  • 1981  (1,608)
  • 1
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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
    Format: application/pdf
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  • 2
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    Constraints on neutrinos and axions from cosmology (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A review is made of the astrophysical arguments with regard to neutrino properties. It is shown that the best fit to the present baryon density and He-4 abundance is obtained with three neutrino species. It is also shown that astrophysical constraints on neutrino and axion lifetime-mass combinations rule out weakly interacting particles with lifetimes between 1/1000 to 10 to the 23rd sec for M up to 10 MeV. There is an allowed astrophysical window for neutrinos with M up to 10 MeV and tau less than 1000 sec. The possible role of massive neutrinos in the dark mass of galaxies is discussed. It is shown that the baryon density in the universe is comparable to the density obtained from the dynamics of binary galaxies. Therefore, massive neutrinos are only required if the cosmological mass density is greater than that implied by binaries and small groups of galaxies. The only objects which might imply such high densities are large clusters. For neutrinos to cluster with these large clusters requires a neutrino mass of at least 3 eV.
    Keywords: ASTROPHYSICS
    Type: Cosmology and particles; Mar 15, 1981 - Mar 21, 1981; Savoie; France
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  • 3
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    Thermonuclear processes on accreting neutron stars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Theoretical models for X-ray burst sources that invoke thermonuclear flashes on the surface layers of an accreting neutron star are discussed. The historical development of X-ray burst observation is summarized, and a physical picture of a neutron star undergoing accretion is drawn. Detailed numerical computations of the evolution of the surface layers of such a star are reviewed. The need for general relativistic corrections to the model is pointed out. Finally, comparisons are made with observations of X-ray bursts, the rapid burster, fast X-ray transients, X-ray pulsars, and gamma-ray burst sources.
    Keywords: ASTROPHYSICS
    Type: Fundamental problems in the theory of stellar evolution; Jul 22, 1980 - Jul 25, 1980; Kyoto; Japan
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  • 4
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    Mass loss from interacting close binary systems (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The three well-defined classes of evolved binary systems that show evidence of present and/or past mass loss are the cataclysmic variables, the Algols, and Wolf-Rayet stars. It is thought that the transformation of supergiant binary systems into the very short-period cataclysmic variables must have been a complex process. The new evidence that has recently been obtained from the far ultraviolet spectra that a certain subclass of the Algols (the Serpentids) are undergoing fairly rapid evolution is discussed. It is thought probable that the remarkable mass outflow observed in them is connected with a strong wind powered by accretion. The origin of the circumbinary clouds or flat disks that probably surround many strongly interacting binaries is not clear. Attention is also given to binary systems with hot white dwarf or subdwarf components, such as the symbiotic objects and the BQ stars; it is noted that in them both components may be prone to an enhanced stellar wind.
    Keywords: ASTROPHYSICS
    Type: Effects of mass loss on stellar evolution; Sep 15, 1980 - Sep 19, 1980; Trieste; Italy
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  • 5
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    Observations of stellar winds in early type stars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The presented review is mainly concerned with the massive population I stars of spectral type OB and the Wolf-Rayet (WR) class. It is pointed out that stellar winds are a ubiquitous phenomenon among the early type stars. Methods to determine the mass loss rate are discussed, taking into account the UV method, the optical method, the infrared method, and the radio method. Current beliefs about early type stars are considered. It is thought that all have stellar winds. The winds are primarily driven by radiation pressure from the UV lines, but other, as yet unknown factors, may determine the density and hence the rates. The stellar winds are highly ionized, more so than would be inferred from their continuum radiation temperatures. The ionization equilibrium in the winds is affected by local X rays which have been detected by the Einstein satellite. Unresolved issues are also pointed out.
    Keywords: ASTROPHYSICS
    Type: Effects of mass loss on stellar evolution; Sep 15, 1980 - Sep 19, 1980; Trieste; Italy
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  • 6
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    Theoretical models of X-ray emission from rich clusters of galaxies (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: After assessing the theory of cluster gas with polytropic equations of state, and discussing the prediction of local polytropic indices in the gas distribution, attention is given to the consequences of modifying the equation of state by thermal cooling in the central regions of the cluster. It is suggested that, if the equation of state can be understood locally, an attempt may be made at (1) predicting the X-ray luminosities of the clusters at distant cosmological epochs and (2) measuring the evolution of the cluster's potential, through observation of the evolution of X-ray luminosity and surface brightness.
    Keywords: ASTROPHYSICS
    Type: In: X-ray astronomy with the Einstein satellite; Jan 28, 1980 - Jan 30, 1980; Cambridge, MA
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  • 7
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    X-ray spectra of clusters of galaxies (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Out of the many individual cases of clusters with spectral complexity reported in the literature, attention is given to the spectral complexity of the most recent data obtained by the Einstein Observatory and an attempt is made to explain at least a portion of the data in terms of models of radiatively-regulated accretion in the central parts of the clusters and/or onto massive galaxies. After a review of the range of models proposed, with emphasis on predicted temperature distribution, it is noted that all accretion models have temperatures which decrease toward the center, and that several authors have explored the consequences of radiative cooling of the gas in the dense central regions of a cluster or of a cluster plus a central galaxy.
    Keywords: ASTROPHYSICS
    Type: In: X-ray astronomy with the Einstein satellite; Jan 28, 1980 - Jan 30, 1980; Cambridge, MA
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  • 8
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    X-ray sources in globular clusters (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Einstein X-ray Observatory globular cluster observation program has completed a survey of 30 clusters, using the HRI detector. Preliminary results are reported for a more sensitive survey being conducted with the imaging proportional counter (IPC) of the satellite, which has found four possible new sources in the first 32 clusters observed. Also described are detailed studies of several luminous, globular cluster sources, including the X-ray burst from Terzan 2, and an effort is made to locate the X-ray sources with respect to cluster centers. Sources of systematic error, required optical studies of globular cluster structure, and the implications of the plausible binary systems for cluster core evolution are discussed.
    Keywords: ASTROPHYSICS
    Type: In: X-ray astronomy with the Einstein satellite; Jan 28, 1980 - Jan 30, 1980; Cambridge, MA
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  • 9
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    Outer atmospheres of late-type stars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent observational results concerning chromospheres and coronae in late-type stars are described. In particular, it is indicated where in the cool half of the HR diagram chromospheres, transition regions, coronae, and large mass loss occur and what the important parameters determining the energy balance of these layers are. The chromospheric modelling process is summarized and models of the late-type supergiants Beta Dra, Epsilon Gem, and Alpha Ori recently computed by Basri and Linsky (1980) are detailed.
    Keywords: ASTROPHYSICS
    Type: PB81-249021 , Physical processes in red giants; Sep 03, 1980 - Sep 13, 1980; Erice; Italy
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  • 10
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    Infrared sources in dense molecular clouds (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent accomplishments in the infrared study of dense molecular clouds are reviewed, and the outstanding problems in the area are discussed. Such questions as whether clouds are collapsing, how they can be classified, and whether star formation is occurring on the edges of clouds are analyzed. Problems of determining size, energy distribution and luminosity, spectral features, evolutionary state, and energetics of infrared sources are discussed.
    Keywords: ASTROPHYSICS
    Type: Infrared astronomy; Jun 23, 1980 - Jun 27, 1980; Kona, HI
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