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  • Inorganic Chemistry  (765)
  • ASTROPHYSICS  (379)
  • Cell & Developmental Biology  (298)
  • SPACE RADIATION
  • SPACE SCIENCES
  • 1975-1979  (1,586)
  • 1970-1974
  • 1960-1964
  • 1978  (1,586)
Collection
Keywords
Publisher
Years
  • 1975-1979  (1,586)
  • 1970-1974
  • 1960-1964
Year
  • 1
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    Interpretation of observed cosmic microwave background radiation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Alfven and Mendis (1977) conclusion that dust grains in galaxies render the universe opaque to cosmic microwave background at a red shift ratio equal to 40 is challenged by a calculation of the opacity of galactic dust grains to the microwave background radiation from the time of decoupling at emission red shift ratio equal to 1500 to the present in the standard big bang model. In the present calculation, evolutionary effects on grain opacity and abundance are estimated. At wavelengths used in studying the microwave background, the optical depth of the grains is found to be 0.18 when the deceleration parameter equals 0.03, and 0.05 when the deceleration parameter equals 0.5. The results indicate that microwave background can provide information on an early dense phase of the universe.
    Keywords: SPACE RADIATION
    Type: Nature; 271; Feb. 2
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  • 2
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    The case for a burst from 3U 0614+09 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A single flare event with a rise time of about 7 s and a decay time of approximately 40 s was observed by the Goddard cosmic X-ray spectroscopy experiment on OSO-8 during observations of 3U 0614+09 in September 1975. The possibility is discussed that the source was 3U 0614+09, which has been compared with the low-mass binary Sco X-1. The spectra during the event could be fitted with blackbody (kT = 0.8-1.1 keV) or thermal bremsstrahlung (kT = 1.1-2.5 keV) models with absorption by cool material. In the blackbody model the source was of the order of 1 million cm in size.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 182
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  • 3
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    Formation of a rotational accretion column (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: We consider the problem of the flow produced by the accretion of gas from a rotating cloud onto a point gravitational source. It is shown that, for a cloud initially in uniform rotation, the effect of accretion is to produce a Taylor column in the cloud parallel to the rotation axis. Only gas within the column is accreted; the gas outside the column undergoes oscillatory flow, which is probably subject to shear instability. The column forms in approximately one-half rotation period from the time at which accretion begins. Its initial radius is determined by the accretion rate and the angular velocity of the cloud. Application of the results to the formation of Jupiter by accretion is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
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  • 4
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    An experimental investigation of the condensation of silicate grains (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are presented for a series of laboratory experiments designed to investigate the nucleation of small silicate grains from a vapor of astrophysically significant elements and compounds. In the experiments, magnesium silicate grains were condensed by simultaneously evaporating Mg and SiO solids into an atmosphere of argon or hydrogen at a pressure of a few torr. The results show that at low temperatures (up to a few hundred degrees C) the condensates are amorphous grains and have widely varying stoichiometries. The thermodynamically most stable compounds (Mg2SiO4, MgSiO3, SiO2) do not form readily, but all initial condensates can be converted to crystalline forsterite (Mg2SiO4) by heating to 1000 C in vacuum. At higher temperatures (above 700 K) it becomes more difficult to nucleate any silicates, and those that do form are amorphous, indicating that surface energies and kinetic effects are very important in determining under what conditions condensation will occur. The IR spectra of the experimentally produced magnesium silicates are found to have a strong resemblance to those observed in many astronomical clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 222
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  • 5
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    Soft X-ray emission from a newly discovered supernova remnant in Cygnus (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 222
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  • 6
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    Background of a shielded Ge(Li) spectrometer at balloon altitudes (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The background data obtained from an actively shielded Ge(Li) spectrometer flown on a balloon were analyzed and a preliminary model was developed to explain background features including the intensity and time profile of line emission. These features can be explained by a combination of secondary radiation originating in the CsI shield and atmospheric secondary radiation leaking through it.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 462-472
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  • 7
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    Gamma-ray line emission above 8 MeV (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The spectra of energetic nuclei within astrophysical sources may be determined by studying gamma-ray line emissions above 8 MeV. Excited states which can be produced by inelastic scattering, charge exchange, and spallation reactions in the abundant nuclear species were considered in order to identify nuclear lines which may contribute to the gamma spectrum. The cross sections for production of most high-energy states are sparsely measured. Those which were determined are comparable to the cross section for production of the 15.11 MeV level in C-12 with few exceptions. The branching ratios for gamma-ray and particle emission are, however, better known. Of those states considered, 44 measured branching ratios greater than 40% for emission of a gamma-ray with energy above 8 MeV. For twelve more states the branching ratios, although not yet determined, are expected to be small. The gamma-ray emission from other individual nuclear states is not likely to be as great as that that for the 15.11 MeV state in C-12.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 323-329
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  • 8
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    Galactic center iron line emission (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Data from the Goddard Space Flight Center experiment on HEAO 1 were examined for galactic center iron line emission. Evidence for a 6.8 keV line from the summed flux within 10 deg longitude and 10 deg latitude of the galactic center was found; however, firm limits cannot be put on the intrinsic line width. If the line emission is diffuse and cosmic-ray-induced, the calculations of Bussard et al (1978) yield an upper limit to c-12 4.44 MeV line emission, which is not inconsistent with the results of Haymes et al (1975). Significant contributions to the iron line from discrete sources can not be ruled out.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 302-309
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  • 9
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    Planetary gamma-ray spectroscopy (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The measured intensities of certain gamma rays of specific energies escaping from a planetary surface can be used to determine the abundances of a number of elements. The fluxes of the more intense gamma-ray lines emitted from 32 elements were calculated using current nuclear data and existing models for the source processes. The source strengths for neutron-capture reactions were modified from those previously used. The fluxes emitted form a surface of average lunar composition are reported for 292 gamma-ray lines. These theoretical fluxes were used elsewhere to convert the data from the Apollo gamma-ray spectrometers to elemental abundances and can be used with measurements from future missions to map the concentrations of a number of elements over a planet's surface. Detection sensitivities for these elements are examined and applications of gamma-ray spectroscopy for future orbiters to Mars and other solar-system objects are discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 98-148
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  • 10
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    Gamma ray spectroscopy in astrophysics: An observational overview (50 keV-20 MeV) (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The observational status of gamma ray astronomy based on results reported prior to April 1978 is discussed. Specific line observations are reviewed from the Sun, the galactic plane, the Galactic Center region, the active Galaxy NGC 5128 (Cen A), the Crab Nebula region, and a transient source in the general direction of the anti-Galactic Center region. A statistical method is described which determines the relative probability that a given, reported observation is due to an external source as compared to a random fluctuation in the experimental background counting rate. Only a few of the many reported observations can be considered likely extraterrestrial observations of an extraterrestrial source made with a confidence level of 99%.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 42-68
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  • 11
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    Gamma-ray lines - A new window to the Universe (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Gamma-ray emission is considered in terms of its usefulness in determining the physics of nucleosynthesis, the interstellar medium, solar flares, supernovae, and neutron stars. The mechanism of gamma-ray line emission is reviewed, i.e., nuclear deexcitation, radiative capture, positron annihilation, and possibly cyclotron radiation in the strong magnetic fields of neutron stars. Various gamma-ray spectra, obtained from balloon and satellite data, are analyzed with attention to solar particle energies and densities, including particle emission from black-hole supernova remnants.
    Keywords: ASTROPHYSICS
    Type: Physics Today; 31; Mar. 197
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  • 12
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    New observations of ultraviolet variability in Wolf-Rayet stars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of ultraviolet variability in Wolf-Rayet stars have been made with the ANS satellite Ultraviolet Photometer Experiment. Significant variations are detected in several of the observed stars, the timescale of the variability ranging from a few minutes to several months.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 183
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  • 13
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    The nature of Aquila X-1 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photometry in the UBV spectra was used to observe Aquila X-1. This X-ray source, usually producing flux on the order of 1-10% that of the Crab Nebula, often behaves in a manner resembling the behavior of galactic X-ray stars. A description of the calibration methods used in the observations is presented, with attention to photoelectric-photographic methods. These observations suggest a quiescent spectral class near Ko, i.e., a dwarf at a distance of 1.6 kpc. The more intense X-ray emissions are said to be generated from internal heating of the stellar atmosphere, with additional energy supplied by a low-mass companion star. This explaination is at variance with the semi-detached Roche model.
    Keywords: ASTROPHYSICS
    Type: Nature; 271; Feb. 16
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  • 14
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    Diffuse gamma radiation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for an investigation of the intensity, energy spectrum, and spatial distribution of the diffuse gamma radiation detected by SAS 2 away from the galactic plane in the energy range above 35 MeV. The gamma-ray data are compared with relevant data obtained at other wavelengths, including 21-cm emission, radio continuum radiation, and the limited UV and radio information on local molecular hydrogen. It is found that there are two quite distinct components to the diffuse radiation, one of which shows a good correlation with the galactic matter distribution and continuum radiation, while the other has a much steeper energy spectrum and appears to be isotropic at least on a coarse scale. The galactic component is interpreted in terms of its implications for both local and more distant regions of the Galaxy. The apparently isotropic radiation is discussed partly with regard to the constraints placed on possible models by the steep energy spectrum, the observed intensity, and an upper limit on the anisotropy.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 222
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  • 15
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    Evidence that cosmic gamma-ray bursts are galactic (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Balloon observations registering scatter angles in a liquid scintillator have revealed gamma-ray bursts having energies as low as 10 to the -7th ergs per square cm. The burst distribution is graphed according to energy and frequency. The hypothesis that the bursts are galactic in origin is in good agreement with their small recorded energies and their predicted distribution on the graph.
    Keywords: ASTROPHYSICS
    Type: Nature; 271; Feb. 16
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  • 16
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    Distance limit for a class of model gamma-ray burst sources (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It is pointed out that MeV photons have actually been observed in bursts. These observations imply that the nonrelativistic sources cannot be further away than a few kpc from the sun and, therefore, must be galactic. The 27 April 1972 event observed by Apollo 16 shows at higher energies a power law spectrum with a possible line feature around 4 MeV. The optical depth of a homogeneous, isotropic radiation field is estimated with the aid of formulae used by Nikishov (1962) and Jauch and Rohrlich (1955). On the basis of an investigation of the various factors involved, it is tentatively suggested that the gamma-ray bursts which have been detected are galactic, but are in the majority of the cases not connected with unique irreversible star transformation. It appears also unlikely that the gamma-ray bursts are connected with galactic novae.
    Keywords: ASTROPHYSICS
    Type: Nature; 271; Feb. 9
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  • 17
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    High resolution spectroscopy from low altitude satellites (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The P 78 1 satellite to be placed in a synchronous polar orbit at an altitude of 550-660 km will carry two identical high resolution spectrometers each consisting of a single (approximately 85 cc) intrinsic germanium IGE detector. The payload also includes a pair of phoswitch scintillators, an array of CdTe detectors and several particle detectors, all of which are mounted on the wheel of the satellite. The intrinsic high purity IGE detectors receive cooling from two Stirling cycle refrigerators and facilitate the assembly of large and complex detector arrays planned for the next generation of high sensitivity instruments such as those planned for the gamma ray observatory. The major subsystems of the spectrometer are discussed as well as its capabilities.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 529-540
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  • 18
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    Theory of the accretion column and cyclotron radiation in X ray pulsars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The energetics of the decelerating matter in the accretion column of X-ray pulsars is considered, in particular the Coulomb process. A two zone model is presented to account for the continuum and cyclotron line emission, incorporating a fan-beam radiation scheme, which appears able to explain the observed properties.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 425-433
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  • 19
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    Cyclotron emission in neutron star magnetospheres (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Kinematic aspects of cyclotron emission in superstrong magnetic fields are reviewed to suggest characteristic features which might be useful in confirming the nature of the reported line feature near 50 keV in the spectrum of Her X-1. The role of the inverse process of cyclotron absorption is also discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 394-403
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  • 20
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    Measurements of 15.11-MeV gamma-ray flux produced in the reactions C-12(p, p')-C-12*(15.11 MeV) and O-16(p, p' alpha)-C-12*(15.11 MeV) (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The flux of 15.11 MeV gamma rays relative to the flux of 4.44 MeV gamma rays which are emitted from the corresponding states of C-12 are a sensitive measure of the spectrum of exciting particles in solar flares and other cosmic sources. Emission of 15.11 MeV gamma rays may result not only from the direct excitation of C-12 but also from the interaction O-16 (p,p' alpha) C-12* sup 15.11 MeV. Although the cross sections for the direct reaction was studied extensively, the cross section for the spallation interaction with O-16 is not reported in the literature. Preliminary measurements demonstrated the feasibility of measuring the production of 15.11 MeV gamma rays by proton interactions with O-16 using the University of Maryland cyclotron facility. For both carbon and oxygen targets the flux of 15.11 MeV gamma rays is being measured relative to the flux of 4.44 MeV gamma rays. The gamma ray emission from de-excitation of the giant dipole resonances is being measured.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 502-511
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  • 21
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    Confidence about line features in Her X-1 spectrum (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A balloon borne X-ray telescope was flown Aire-surl'Adour, France to search for pulsation of the X-ray source HER X1. The source was measured for about 3500 s relative exposure larger than 0.75 and features were detected at 57.5 plus or minus 7.5 keV and 135 plus or minus 10 keV in the spectrum. Data were reanalyzed in terms of possibility of gain shift encoder. The very strong dependence of the line features on such a shift is discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 346-370
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  • 22
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    Gamma-ray lines from neutron stars as probes of fundamental physics (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The detection of gamma-ray lines produced at the surface of neutron stars will serve to test both the strong and gravitational interactions under conditions unavailable in terrestrial laboratories. Observation of a single redshifted gamma-ray line, combined with an estimate of the mass of the star will serve as a strong constraint on allowable equations of state of matter at supernuclear densities. Detection of two redshifted lines arising from different physical processes at the neutron star surface can provide a test of the strong principle of equivalence. Expected fluxes of nuclear gamma-ray lines from accreting neutron stars were calculated, including threshold, radiative transfer and redshift effects. The most promising probes of neutron star structure are the deuterium formation line and the positron annihilation line. Detection of sharp redshifted gamma-ray lines from X-ray sources such as Cyg X-1 would argue strongly in favor of a neutron star rather than black hole identification for the object.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 275-282
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  • 23
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    Supernovae and the formation of the solar system (1978)
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    Publication Date: 2011-08-17
    Description: The evidence that a supernova explosion may have triggered the formation of the solar system is reviewed. It cannot be said on the basis of the investigation that the supernova trigger is absolutely necessary for planetary system formation. However, it does appear according to the isotopic evidence that a supernova did blow up within a few million years of the solidification of objects in the solar system. If such an event occurred, it is reasonable to assume that the resultant supernova shock had a causal connection with the formation of the solar system and that a supernova may be one stimulus for formation of low-mass stars.
    Keywords: ASTROPHYSICS
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  • 24
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    Star formation in molecular clouds (1978)
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    Publication Date: 2011-08-17
    Description: A general overview is presented of the findings of molecular line and infrared astronomy regarding star formation. Beginning with the statement that stars, and therefore, planets, form from molecular clouds, it is argued that the growing body of data on conditions in molecular clouds should serve as input parameters for theoretical calculations of star and planet formation. The fact that the gravitational potential energy of molecular clouds far exceeds their thermal energy implies that the required rate of star formation is easily explained. Indeed the most important problem in this field is that the rate of star formation predicted from molecular cloud studies is too high. Until this problem is understood, additional modes of inducing star formation, while they may be occurring, only add to the existing difficulties.
    Keywords: ASTROPHYSICS
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  • 25
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    The cloudy state of interstellar matter (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The expression 'cloudy state' is used to describe the state of the diffuse interstellar matter, with emphasis on its denser and more opaque regions. Questions of morphology with respect to the Galaxy are examined, taking into account neutral hydrogen, molecular regions, H II regions, infrared sources and masers, coronal gas in the Galaxy, and the major components of the interstellar medium. Aspects of dynamics are also considered, giving attention to the two-phase interstellar medium, the three-phase interstellar medium, the density-wave compression of clouds, and problems related to the concept of collapsing clouds. Developments concerning chemistry are explored. Radioactive chronologies are discussed along with isotopic anomalies and aspects of interstellar chemistry.
    Keywords: ASTROPHYSICS
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  • 26
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    Some implications for interstellar molecules of a low electron abundance in dense clouds (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 83; Dec. 197
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  • 27
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    Discovery and optical identification of 2S0921-630 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The discovery of a faint X-ray source at approximately 282 deg galactic longitude, -9 deg galactic latitude with the rotation modulation collimator X-ray detectors aboard SAS 3 is reported. The source is designated 2S 0921-630 and is tentatively identified, on the basis of an optical search, with a 17th magnitude star exhibiting the He II line at 4686 A and H-beta in emission. The optical spectrum of this star is shown to be similar to those of the optical counterparts of Sco X-1 and other such galactic X-ray sources. It is suggested that 2S 0921-630 may belong to the class of low-luminosity galactic X-ray binaries.
    Keywords: ASTROPHYSICS
    Type: Nature; 276; Dec
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  • 28
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    Hard X-rays from U Geminorum (1978)
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    Publication Date: 2011-08-17
    Description: The A-2 experiment on HEAO 1 has discovered that the dwarf nova U Geminorum can be a weak source of hard X-rays at optical maximum. During the outburst in October 1977, when a strong soft X-ray flux was discovered, a 2-10-keV flux was also observed. Evidence is presented that this flux appeared with the rise to optical maximum, about half a day before the soft X-rays appeared, and persisted about 2 days. During these first 2 days of the outburst the average flux was 2.4 x 10 to the -11th erg/sq cm per sec, corresponding to a luminosity of 2.8 x 10 to the 31st erg/s for a distance of 100 pc and an absorbed thin thermal spectrum with kT of about 5 keV. During optical minimum an OSO 8 upper limit implies a luminosity less than 10 to the 31st erg/s. Restrictions on models of U Geminorum are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 226
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  • 29
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    Ice mantles and abnormal extinction in the Rho Ophiuchi cloud (1978)
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 226
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  • 30
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    Gamma-ray astrophysics - A new look at the universe (1978)
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    Publication Date: 2011-08-17
    Description: Gamma-ray astronomy, which may be defined to include the spectral region from above 100 keV to about 1000 GeV, permits investigation of the most energetic photons originating in the Galaxy and beyond. These observations provide the most direct means of studying the largest transfers of energy occurring in astrophysical processes, including the dynamic effects of the energetic charged cosmic-ray particles, element synthesis, and particle acceleration. Further, gamma-rays suffer negligible absorption or scattering as they travel in straight paths. Hence they may survive billions of years. Studies of the spatial, temporal, and energy distribution of cosmic gamma-rays will, therefore, provide fundamental new information for resolving some of the major problems in astrophysics today. Attention is given to the gamma-ray observations of the solar system, stellar objects, diffuse gamma-ray emission from the Galaxy, other galaxies and cosmology, and future prospects.
    Keywords: ASTROPHYSICS
    Type: Science; 202; Dec. 1
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  • 31
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    Methane detected in Orion A (1978)
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    Publication Date: 2011-08-17
    Description: This letter reports the detection of line emission from the Orion Molecular Cloud corresponding to six distinct pure-rotational delta J = 0 transitions in CH4. The transitions observed and the transition frequencies are: J = 11 E(2) - E(1), 4600.359 MHz; J = 18 F1(4) - F2(1), 76,231.45 MHz; J = 18 A1(2) - A2(1), 76,700.02 MHz; J = 19 F1(4) - F2(1), 75,944.99 MHz; J = 19 F2(4) - F1(1), 78,233.59 MHz; and J = 20 F2(5) - F1(2), 82,873.59 MHz. The observed spectra at the six transition frequencies are plotted, and all but two of the methane lines are found to be very narrow (about 2 km/s). It is noted that the small velocity widths of the four weaker lines and an observed variability of the J = 18 A line are classic characteristics of a maser and that the excitation appears to be nonthermal. An effective excitation temperature of 1100 to 2100 K is estimated for the methane in Orion A.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 226
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  • 32
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    Predicted color excess ratios versus interstellar grain size (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Various color excess ratios, the ratio (R) of total to selective extinction, and values of the wavelength of maximum interstellar linear polarization (lambda max) are computed and displayed as functions of mean interstellar grain size and absorption coefficients. E(V-K)/E(B-V)-E(u-b)/E(b-y) is shown to be highly sensitive to changes of mean grain size. The shape of the R versus lambda max curve is shown to depend on the amount of absorption initially present in the grains, and on the absorptivity of the material added to the grains. While no simple model of grain growth has been found to fit all the observations, the two stars with the largest values of lambda max (HD 147889 and W67) support the concept of dielectric mantles growing on dielectric grains. It is further shown that more accurate uby and JKL photometry of heavily reddened stars would permit better discrimination between grain growth theories.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 33
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    Interaction between emission-line filaments and highly energetic explosions in QSOs (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The conditions under which QSO line-emitting regions can survive a relativistic explosion are investigated along with the question of whether past and future observations can place constraints on both predicted highly energetic outbursts of ultrarelativistic plasma or LF electromagnetic radiation and the line-emitting gas. Observed properties of QSO emission-line regions are reviewed, and the interaction between a relativistic explosion and a dense cloud is analyzed for the cases of a sudden release of relativistic plasma and an outburst of LF electromagnetic waves. Bremsstrahlung X-ray emission from shocked QSO filaments is calculated, the evolution of dense QSO clouds is examined, and radiative acceleration is excluded as the process responsible for the high bulk velocities of filaments, at least in sources that display energetic outbursts. An alternative mechanism involving highly energetic explosions is proposed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 34
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    Gas flow in the barred spiral galaxy NGC 5383 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Line-of-sight gas velocities calculated from a numerical hydrodynamical model of a barred spiral galaxy are compared with the observations and models made by Peterson, Rubin, Ford, and Thonnard of the gas flow in NGC 5383. The hydrodynamical model provides a somewhat better fit to the observations of NGC 5383 than does their symmetric, warped-disk model. It is argued that the basic model appropriate to understanding the gas motions in barred spiral galaxies is not circular rotation but rather a characteristic elliptical pattern of flow.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 35
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    The formation of molecules in interstellar clouds from singly and multiply ionized atoms (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The suggestion is considered that multiply ionized atoms produced by K- and L-shell X-ray ionization and cosmic-ray ionization can undergo ion-molecule reactions and also initiate molecule production. The role of X-rays in molecule production in general is discussed, and the contribution to molecule production of the C(+) radiative association with hydrogen is examined. Such gas-phase reactions of singly and multiply ionized atoms are used to calculate molecular abundances of carbon-, nitrogen-, and oxygen-bearing species. The column densities of the molecules are evaluated on the basis of a modified version of previously developed isobaric cloud models. It is found that reactions of multiply ionized carbon with H2 can contribute a significant fraction of the observed CH in diffuse interstellar clouds in the presence of diffuse X-ray structures or discrete X-ray sources and that substantial amounts of CH(+) can be produced under certain conditions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 36
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    On the origin of Hawking mini black-holes and the cold early universe (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A simple argument is outlined leading to the result that the mass of mini black holes exploding today is 10 to the 15th power g. A mathematical model is discussed which indicates that the equation of state is greatly softened in the high-density regime and a phase transition may exist, such that any length (particularly very small sizes) will grow with time irrespective of its relation to the size of the particle horizon. It is shown that the effect of spin-2 mesons with respect to the equation of state is to soften the pressure and make it negative. An analytical expression is given for the probability that any particular region in a hot early universe will evolve into a black hole.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 184
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  • 37
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    The 3 K blackbody radiation, Dirac's Large Numbers Hypothesis, and scale-covariant cosmology (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A program is described which is intended to derive a generalized system of gravitational equations that allow (but do not require) G to vary, to use the 3-K blackbody radiation to fix the relation between G and the gauge function, and to employ Dirac's (1937) Large Numbers Hypothesis to derive the geometry of the universe. Einstein's equations are retained in their total integrity, but the specification is made that they are valid only when gravitational units are used. A scale-invariant form of Einstein's equations is obtained, and from this are derived the energy conservation law, the baryon-number conservation law, and the appropriate cosmological equations. Dirac's proposals of 1937 and 1973 are incorporated into the formalism, and a gauge based on consolidation of the 3-K blackbody radiation is presented. A unique solution for the geometry of the universe is determined for zero curvature solely from the 3-K radiation and the Large Numbers Hypothesis; this solution predicts a deceleration parameter exactly equal to unity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 224
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  • 38
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    Physics of the primitive solar nebula and of giant gaseous protoplanets (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It has been proposed that the supernova responsible for injecting Al-26 into the early solar system was in fact responsible for triggering the collapse of an interstellar cloud in order to produce a system of stars, one of which would be the solar system. Details concerning the mechanism involved in such a process are discussed. Attention is given to the evolution of the primitive solar nebula, the instabilities in the primitive solar nebula, and the giant gaseous protoplanets. The principal conclusion to be drawn from the material presented is that the primitive solar nebula was a rather chaotic place, highly turbulent, with the multiple formation of giant gaseous protoplanets.
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  • 39
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    Fragmentation of molecular clouds (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Fragmentation is generally considered to be the initial process that a molecular cloud must undergo before stars can form. Yet its role in determining the final mass spectrum remains obscure. It appears that gravitational fragmentation, considered as a unique process, is unsatisfactory. Both fragmentation and complementary physical processes are, therefore, discussed. One of the principle aims of the discussion is to indicate how stars of solar mass (and more generally, how the initial mass spectrum of stars) can form. Attention is given to the evidence for fragmentation, opacity-limited fragmentation, magnetic flux-limited fragmentation, fragmentation induced by molecule formation and excitation, protostellar heat input, fragment coalescence, accretion, binary formation, and probabilistic theories.
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  • 40
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    Numerical calculations of protostellar hydrodynamic collapse (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Although 1-D (spherically symmetric) experiments of protostar collapse are highly idealized, they are the only ones which have been carried to a stage where a 'stellar' object is formed. Experiments have shown that the parameters (e.g., radius and luminosity) of the visible stellar core are sensitive to the assumed initial conditions, particularly the initial density. One of the major findings of 2-D numerical experiments is the formation of rings. Three-dimensional hydrodynamical calculations indicate that a collapsing cloud will break up into two or more orbiting subcondensations with the possible subsequent development of a stellar multiple system.
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  • 41
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    Condensation processes and the formation of cosmic grains (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The case of condensation from a gas in the absence of any preexisting grains or nuclei upon which condensation can occur is considered. Some of the analysis is expected to apply to condensation on grains already present. An attempt is made to examine the basic assumptions of the various procedures used to describe condensation and to examine their applicability to astronomical systems. Attention is given to thermodynamic equilibration calculations, nucleation theory, kinetic mechanisms, the theoretical mechanisms, and condensation experiments.
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  • 42
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    The observational status of the Beta Cephei stars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Beta Cephei stars are a group of variables of spectral type B, whose light and radial velocity periods lie between about three and seven hours. An up-to-date summary of the observational data for individual stars considered to be members of the Beta Cephei group is provided. The general properties of Beta Cephei stars as determined from a comparison between theory and observation are considered, taking into account location in the HR diagram and evolutionary state, physical properties, statistics and galactic distribution, and period-luminosity relation and pulsation mode. Recent trends concerning the observation of Beta Cephei stars are examined, giving attention to a search for new variables, ultraviolet observations from spacecraft, and high-resolution studies of profile variations.
    Keywords: ASTROPHYSICS
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  • 43
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    The central, compact source in the Cygnus A galaxy (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Single, optically thin, component models as well as double, optically thick at low frequencies, component models have been examined in trying to explain the central source in the nucleus of Cygnus A. In the course of exploring those models, it is found that this compact radio source may be quite similar to other compact and variable sources in Seyfert galaxies and quasars. Double component models generally do better because they fit the X-rays, and there is a good chance that the X-rays arise in the central source; these models can naturally explain variability which may already have been detected in X-rays. The IR is most likely due to emission by cold dust in the nucleus of Cygnus A. Optical emission is, very likely, primarily thermal, except perhaps at UV wavelengths. A number of observations are suggested to check the predictions of this work.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 44
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    Optical detection of local interstellar particles during an out-of-ecliptic mission (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A proposed NASA/ESA 'out of ecliptic' mission for placing limits on the brightness of the interstellar (IS) relative to the interplanetary (IP) component of zodiacal light is discussed. The brightness integral used to estimate the monochromatic is introduced, and it is explained that, although the interstellar contribution is below the limit of detectability for earth-based measurements, sunwards viewing from a spacecraft located at a distance of 1 AU would be able to detect the IS component. The color difference between the IS and IP components is considered in an analysis of the upper limit of IS component detectability.
    Keywords: ASTROPHYSICS
    Type: Nature; 275; Sept. 7
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  • 45
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    Relativistic blast-wave model for the rapid flux variations of AO 0235+164 and other compact radio sources (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A relativistic blast-wave version of a signal-screen model is developed which can adequately explain the details of the flux-density and structural variations of compact extragalactic radio sources. The relativistic motion implied by flux variations is analyzed with respect to the synchrotron spectrum of the BL Lac object AO 0235+164 observed during outbursts, and a signal-screen model for rapidly expanding shells produced by ultrarelativistic blast waves is examined. The approximate observed structure of the blast wave at three stages in its evolution is illustrated, each stage is described, and the model is applied to the flux density outburst in AO 0235+164 observed in late 1975. The results show that a relativistic blast-wave model can in general reproduce the main features of the observed flux variations in compact sources. Some problems with the proposed model are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 224
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  • 46
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    Relative abundance of antiprotons and antihelium in the primary cosmic radiation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper reports measurement of the antiproton-to-proton and antihelium-to-helium ratios in the 4-100 GeV/c range. A superconducting magnet spectrophotometer obtained the data during a balloon flight in May 1976. The upper limit value for the antiproton ratio is 0.0005 in the 4.2-12.5 GeV/c range. This value is only slightly higher than the expected value for a leaky box-model and nearly equal to the value expected in the Peter-Westergard model. It is suggested that this upper limit value rules out the closed galaxy model. Upper limit values for the antihelium ratio are 0.000058 in the 4-10 GeV/c range; less than 0.0001 in the 4-33 GeV/c range; and less than 0.01 in the 33-100 GeV/c range. The interpretation of the raw data is explained.
    Keywords: SPACE RADIATION
    Type: Nature; 274; July 13
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  • 47
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    The infrared source associated with Sh 2-149 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations at optical and infrared wavelengths of the bright infrared point source in the direction of Sh 2-149 are used to determine a spectral type (M1) and luminosity class (Ib-II) for the object. These observations contradict the suggestion of Bergeat et al. (1975) that the object is a highly reddened O star. The estimated visual extinction (approximately 5-7 magnitudes) and luminosity class derived from the present observations are used to estimate the distance (about 1-3 kpc) to the infrared source.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 67; 2, Ju; July 197
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  • 48
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    Ionization of interstellar H2 clouds by supernovae (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Two destruction mechanisms for molecular hydrogen in the H I regions of the interstellar medium were given by Stecher and Williams (1967). The first is dominant in weak radiation fields and involves photon excitation (at about 1000 A) to the first excited electronic state with a subsequent decay into the vibrational continuum of the ground state. The second destruction mechanism is dominant in the strong photon fields that exist when a supernova explosion occurs. It involves photoionization (at about 1000 A) from metastable high vibrational levels produced by photon excitation (in the same wavelength range) to an excited electronic state and subsequent decay to bound vibrational levels. It is shown that ionization of molecular hydrogen can occur at considerable distances from such supernova events while the atomic hydrogen remains neutral. The effect should be observable in the dispersion measures of new pulsars.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 67; 1, Ju; June 197
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  • 49
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    Interplanetary gas. XXII - Plasma tail disconnection events in comets - Evidence for magnetic field line reconnection at interplanetary sector boundaries (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Attention is focused on a form of cometary activity which has been known for some time but is poorly understood: the discarding of a plasma tail by a comet. A link is found between plasma-tail rejections and conditions in the solar wind. A model is presented in which a disconnected tail is the end result of magnetic-field-line reconnection in the cometary ionosphere caused by the traversal of a magnetic sector boundary. Observations of plasma tails appear to be the best and only method at present of mapping the interplanetary sector structure out of the ecliptic plane.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 223
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  • 50
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    Hercules X-1 = HZ Herculis - A multiperiod variable (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Fundamental rotation properties of the free modes of oscillation of a star are employed to account for the various periodicities observed in the X-ray binary system HZ Her/Her X-1. The various rotation rates may be taken as defining a set of beat periods associated with the quasiregular flareups of HZ Her. This analysis, involving only one free parameter, provides a single physical mechanism to explain five observed periods of the binary system, including periods of 1.7 days, 35 days and 10 to 12 years.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
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  • 51
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    The rocket-ultraviolet spectrum and models of the planetary nebula NGC 7662 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Ultraviolet spectral analysis of NGC 7662 has revealed a Balmer line distribution indicating a C/O ratio of unity. This abundance of carbon is characteristic of mixing between the central star and the outer envelope of the planetary nebula. A continuum spectrum is observed from the star and the nebula, radiating its energy via the two photon process through neutral hydrogen. Spectral lines were fitted to apply to the predictions of three models of the nebular structure. UV observations were compared with visible, IR, and radio observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
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  • 52
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    The ISEE-C gamma ray burst spectrometer (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The technical properties, operation, and expected sensitivity are discussed for an experiment intended to search for narrow lines in the spectra of gamma ray bursts during the ISEE-C mission. At the heart of the experiment is a radiatively cooled germanium solid state photon detector. The instrumentation is capable of storing the entire spectrum of all but the largest bursts in the energy range 0.05-6.5 MeV. In addition, it analyzes the signals from two CsI detectors in two other experiments on the spacecraft and records event time histories from these to a few millisecond accuracy. A background mode permits spectral analysis during quiet times and will allow the determination of physically interesting upper limits for narrow lines in the diffuse gamma ray background radiation.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 516-528
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  • 53
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    The excitation of electronic transverse energy levels in an intense magnetic field (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of the X-ray pulsar Hercules X-1 show a line emission feature at about 60 keV, which has been interpreted as the fundamental electron cyclotron line in a magnetic field of around six trillion gauss. In this interpretation, the line radiation results from transitions between transverse energy levels, which are quantized by the field. The expected line luminosity from the excitation of these levels by protons which are falling into the polar cap of a neutron star are calculated. They are assumed to attain kinetic energies up to around 200 MeV, the gravitational potential energy at the surface. The cross sections for high energy Coulomb encounters between small pitch angle protons and electrons in a strong field are measured and used to calculate the energy loss rate of the infalling protons. This rate, together with the rate of elastic nuclear proton collisions, is then used to calculate the number of line photons an infalling proton can be expected to produce, directly or indirectly. The results are applied to Hercules X-1.
    Keywords: SPACE RADIATION
    Type: ma Ray Spectry. In Astrophys.; p 404-417
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  • 54
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    Cyclotron lines from Her X-1 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Data obtained during four balloon flight observations of hard X-ray emission from Her X-1 provide strong support for the existence of a spectral line feature at 54 keV to 58 keV, while the existence of a second harmonic is uncomfirmed. Because it is difficult to explain the observed feature by a second continuum spectrum or by atomic or nuclear processes, an interpretation in terms of a cyclotron line seems likely. There are two possibilities. There may be a cyclotron absorption feature at approximately 42 keV, and a possible second one at approximately 80 keV. In particular there may be a rather broad absorption feature between the spectral break (25 keV) and approximately 40 keV.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 331-345
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  • 55
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    Gamma ray spectroscopy in astrophysics: Solar gamma ray astronomy on solar maximum mission (1978)
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    Publication Date: 2011-08-17
    Description: The SMM gamma ray experiment and the important scientific capabilities of the instrument are discussed. The flare size detectable as a function of spectrum integration time was studied. A preliminary estimate indicates that a solar gamma ray line at 4.4 MeV one-fifth the intensity of that believed to have been emitted on 4 August 1972 can be detected in approximately 1000 sec with a confidence level of 99%.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 558-574
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  • 56
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    Search for broad gamma ray lines with the UCR double Compton scatter telescope (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The operation of a double scatter telescope and the evaluation of data obtained during a 24 hour balloon flight are discussed. An increase in gamma rays was observed as the galactic anti-center crossed the aperature of the telescope. Searches for lines from p(n,gamma)d at 2.2 MeV, C-12* at 4.4 MeV and on -16* at 6.1 MeV and for other lines broadened or redshifted are being conducted to identify the processes responsible for the production of celestial gamma rays. Two upper limits for lines in the angalactic anti-center direction at 4.4 MeV and 6.1 MeV are 6 and 4 x 10 to the minus 4 power gamma/sq cm-s.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 217-222
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  • 57
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    Nuclear gamma rays from stellar flares (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Solar flare observations are consistent with the phenomenological description that a loop of magnetic flux is convected to the surface of the star and twisted. The resulting inductive current parallel to the field is dissipated at an enhanced rate throughout the field volume by current limiting instabilities. The steady state balance between joule heating and thermal conduction along the field lines of force to the denser, cooler surface establishes a temperature distribution. The expansion of heated and ionized surface layers leads to a pressure balance and hence predictable density and X-ray emission measure. The current limitation instabilities result observationally in the parallel current being transferred to run-away ions that reach a kinetic energy of some finite fraction of the inductive potential drop. The nuclear excitation gamma rays produced by such a run-away ion current are calculated for a white dwarf flare.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 149-167
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  • 58
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    Mechanisms and sites for astrophysical gamma ray line production (1978)
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    Publication Date: 2011-08-17
    Description: The production of gamma ray lines and estimates of line fluxes resulting from nuclear deexcitations, positron annihilation, and electron capture at various astrophysical sites are discussed. Supernova and nova explosions synthesize long-lived radioactive isotopes and eject them into space where they produce observable gamma ray lines by decaying into excited levels of daughter nuclei or by emitting positrons. Energetic charged particles in the interstellar medium, in supernova remants, in solar or stellar flares, and possibly in the vicinity of compact objects, produce gamma-ray lines by inelastic collisions which either excite nuclear levels or produce positrons and neutrons. Energetic particles can result from acceleration in time-varying magnetic fields (solar flares) or from gravitational accretion onto neutron stars and black holes. Electromagnetic processes in the strong magnetic fields of pulsars can produce positron-electron pairs, with line emission resulting from positron annihilation. Deexcitations of quantized states in strong magnetic fields can also produce lines.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 7-41
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  • 59
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    The transfer of cyclotron lines through the magnetospheric shell of Hercules X-1 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Cyclotron emission from a strong magnetic field, has been proposed to identify line feature observed in the hard X-ray spectrum of the neutron star Hercules X-1. If this interpretation is indeed correct, and if the model wherein the 1.24 second hard X-ray pulse is due to the occultation of a more isotropic X-ray flux by an opaque magnetospheric shell is accepted then these observations can be used to place strict limits on the total source luminosity of the cyclotron emission. The observational fate of cyclotron line photons that have emerged from the region near the neutron star surface, but have yet to encounter an opaque shell at the magnetosphere is discussed. It is shown that if a narrow line is incident on such a shell, then a residual narrow feature can emerge from the shell.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 418-424
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  • 60
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    Low energy gamma ray observations with the MPI-Compton telescope (1978)
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    Publication Date: 2011-08-17
    Description: Although the evaluation of data from the first balloon-flight of a large area Compton telescope is incomplete, two preliminary results are discussed. From the measured background spectrum at float altitude, the sensitivity of the telescope for the detection of cosmic gamma ray lines is estimated. The energy spectra is determined for an enhanced gamma ray flux observed from the direction of the Seyfert galaxy NGC 4151. A schematic drawing of the telescope is presented and discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 207-216
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    Detection of 511 keV positron annihilation radiation from the galactic center direction (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A balloon-borne gamma ray telescope with an approximately 130 cu cm high purity germanium detector was flown over Australia to detect sharp spectral features from the galactic center direction. A 511 keV positron annihilation line was observed at a flux level of (1.21 plus or minus 0.22) x (10/cu cm) photons/sec/sp cm. Suggestive evidence for the detection of the three-photon positronium continuum is presented. The possible origin of the positrons is discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 169-189
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  • 62
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    The light curve of the nucleus of comet d'Arrest (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper reports new photoelectric photometry of the nucleus of P/d'Arrest (1976e) during August 4, 5, and 6, 1976 (UT), just before perihelion passage. The comet appeared as a bright stellar nucleus with a faint surrounding coma. The average visual magnitude from the nuclear region (16-arcsec diaphragm) was 11.60. The visual brightness varies with an amplitude of 0.15 plus or minus 0.02 mag. There is evidence for a period of 5.17 plus or minus 0.01 hr. We interpret such a periodic variation as due to the rotation of the nucleus. The colors of the nuclear region are very similar to those of a solar-type star, and they do not vary significantly with aspect angle.
    Keywords: ASTROPHYSICS
    Type: Icarus; 34; Apr. 197
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  • 63
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    Superdense neutron matter (1978)
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    Publication Date: 2011-08-17
    Description: A relativistic theory of high-density matter is presented which takes into account the short-range interaction due to the exchange of spin-2 mesons. An equation of state is derived and used to compute neutron-star properties. The prediction of the theory for the values of maximum mass and moment of inertia for a stable neutron star are 1.75 solar masses and 1.68 by 10 to the 45th power g-sq cm, in very good agreement with the presently known observational bounds. The corresponding radius is found to be 10.7 km. It is found that the inclusion of the spin-2 interaction reduces the disagreement between the relativistic and nonrelativistic theories in their predictions of masses and moments of inertia.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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  • 64
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    Computer simulation of the velocity diffusion of cosmic rays (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Monte Carlo simulation experiments have been performed in order to study the velocity diffusion of charged particles in a static turbulent magnetic field. By following orbits of particles moving in a large ensemble of random magnetic field realizations with suitably chosen statistical properties, a pitch-angle diffusion coefficient is derived. Results are presented for a variety of particle rigidities and rms random field strengths and compared with the predictions of standard quasi-linear theory and the nonlinear partially averaged field theory.
    Keywords: SPACE RADIATION
    Type: Physics of Fluids; 21; Mar. 197
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  • 65
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    Some problems with the interpretation of recent microwave background observations in the direction of galaxy clusters, or, beware of negative antenna temperatures (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Recently reported observations of the 3-K microwave background in the direction of rich clusters of galaxies should be viewed as placing stringent limits on the mass of cooler ionized gas within the clusters, rather than as a verification of thermal bremsstrahlung models for cluster X-ray sources. At the high radio frequencies employed in the observations, there is a positive contribution to the observed source-brightness distributions from free-free emission by any cooler gas. This can overwhelm the anticipated inverse Compton diminution of the background radiation, even when the total mass in cooler gas is significantly less than the mass of hot plasma required to explain the X-ray source. Future experiments of this type should be conducted only when atmospheric stability is sufficient to permit lengthy drift scans across the clusters. Extreme care must be taken to remove the contributions from any discrete sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 220
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  • 66
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    An interstellar cloud density from Copernicus observations of CO in the spectrum of Zeta Ophiuchi (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Interstellar CO absorption bands in Copernicus spectra of Zeta Oph have been studied. Absorption profiles, computed under the assumption that excitation is due to collisions with H2 molecules and interaction with the 3-K background radiation field, were fitted to the reduced data of nine bands. When a gas kinetic temperature of 56 K is assumed, the best-fit condition implies a hydrogen-nucleus density of 120 per cu cm, a CO column density of 1.2 by 10 to the 15th power per sq cm, and a radial-velocity dispersion of 0.9 km/s. The relevance of these results to existing ideas concerning the Zeta Oph interstellar clouds is discussed. It is suggested that the strongest interstellar component is not circumstellar in origin but is instead part of a supernova remnant. Simple calculations are made to establish the plausibility of the supernova-remnant identification. This suggestion is also supported by Heiles's (1976) 21-cm pictures.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 220
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  • 67
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    Heliocentric distance dependence of the interplanetary magnetic field (1978)
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    Publication Date: 2011-08-17
    Description: Numerous spacecraft measurements bearing on the heliocentric distance dependencies of both large- and small-scale properties of the interplanetary magnetic field (IMF) are assembled and compared. These data tend to indicate that the average of the radial field component varies as the inverse square of distance. However, the azimuthal component is rather strongly a function of time, being influenced by both the time-dependent solar wind speed and the evolution of the source field at the sun. Thus, unless the solar wind speed dependence is taken into account, individual sets of measurements by a single spacecraft give an azimuthal component gradient which is steeper than the inverse distance dependence predicted from the Parker spiral model. A least squares fit to the composite (five spacecraft) solar rotation average data set gives a result close to the inverse distance dependence. Preliminary Helios results suggest general consistency with the spiral model.
    Keywords: ASTROPHYSICS
    Type: Reviews of Geophysics and Space Physics; 16; Feb. 197
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  • 68
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    ISAs and the dwarf content of the inner nuclear regions of M31 (1978)
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 37; May 1978
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  • 69
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    On the detection of newly created CN radicals in comets (1978)
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    Publication Date: 2011-08-17
    Description: A description is presented of laboratory measurements concerning the amount and the distribution of energy released into newly formed radicals by the photodissociation process. The experimental method used involved flash photolysis of the parent compound followed by laser induced fluorescence detection of the CN fragment. This method allowed the detection of individual rotational lines and, thereby, a monitoring of the relative populations of the vibrational-rotational levels of the CN ground state. The results obtained in the investigation suggest the possibility of observing emission lines in cometary spectra from newly formed CN radicals. Calculations show that it is feasible with present observational techniques to detect photochemically excited lines in the 0-0 band of the violet system.
    Keywords: ASTROPHYSICS
    Type: Icarus; 34; May 1978
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  • 70
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    Nova-driven winds in globular clusters (1978)
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    Publication Date: 2011-08-17
    Description: Recent sensitive searches for H-alpha emission from ionized intracluster gas in globular clusters have set upper limits that conflict with theoretical predictions. It is suggested that nova outbursts heat the gas, producing winds that resolve this discrepancy. The incidence of novae in globular clusters, the conversion of kinetic energy of the nova shell to thermal energy of the intracluster gas, and the characteristics of the resultant winds are discussed. Calculated emission from the nova-driven models does not conflict with any observations to date. Some suggestions are made concerning the most promising approaches for future detection of intracluster gas on the basis of these models. The possible relationship of nova-driven winds to globular cluster X-ray sources is also considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 222
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  • 71
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    Plasma electron observations in the wake of Venus (1978)
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    Publication Date: 2011-08-17
    Description: Two plasma regimes were observed in the Venus wake, one characterized by negative-going anisotropies accompanied by high bulk speeds and low magnetic variance, and the other characterized by positive-going anisotropies accompanied by low bulk speeds and high magnetic variance. The two modes alternate in time in a stochastic bimodal fashion as interplanetary magnetic field discontinuities propagate past Venus and switch on the positive anisotropies. The positive mode probably represents enhanced planetary ion pickup which results in instabilities, the damping of which energizes the electrons in the distant wake.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 83; Apr. 1
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  • 72
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    Thermal continuum from acretion disks in quasars (1978)
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    Publication Date: 2011-08-17
    Description: It is argued that supermassive accretion in disks may explain the flat optical continuum observed from some QSOs and Seyfert galaxies. With the aid of energy considerations it is shown that a luminous QSO may be powered by accretion onto a black hole with a mass corresponding to that of 100 million solar masses. It is proposed that the blue continuum component of 3C 273 is thermal continuum emission from the inner part of an accretion disk that powers 3C 273. The present model suggests that many QSOs and Seyfert galaxies may show a power law continuum plus thermal emission from the disk at optical or UV frequencies. Many such objects show indeed a flattening or upturn of their continua in the blue. The QSO PHL 957 shows a flat continuum and indications of a cutoff at the highest observed frequencies.
    Keywords: ASTROPHYSICS
    Type: Nature; 272; Apr. 20
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  • 73
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    Interplanetary gas. XXII - Interaction of comet Kohoutek's ion tail with the compression region of a solar-wind corotating stream (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An apparently successful identification of a comet-tail feature with a solar-wind event is presented. Photographs of comet Kohoutek 1973f show a large-scale disturbance in the middle and outer regions of the ion tail early on January 20 of 1974. On the previous and succeeding days the comet had, however, a 'normal' and less active appearance. The peculiar tail structure is linked to an encounter with rapidly changing solar-wind conditions on the forward edge of the high-velocity solar-wind stream which encountered the earth late on January 24. The stream produced a geomagnetic storm of the recurrent type. The high-speed stream appears to have been associated with a large near-equatorial coronal hole which underwent central meridian passage on January 22. It is proposed that the comet was in the compression region on the stream forward edge at the time of formation of the tail disturbance. The accuracy of the time delays is actually tested by an application of the wind shock theory of ionic tail orientations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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  • 74
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    Extended observations of Vela X-1 by OSO 8 (1978)
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    Publication Date: 2011-08-17
    Description: The Goddard Space Flight Center (GSFC) Cosmic X-Ray experiment aboard OSO 8 viewed the X-ray binary pulsar, Vela X-1, on three occasions from late 1975 through late 1976. The X-ray spectrum is well-represented by a power law modified by photoelectric absorption, a high-energy cutoff, and a line feature at about 6.8 keV. When combined with other observations, the reported measurements show that the pulse period is not decreasing monotonically. The three eclipses observed all indicate a significant eclipse flux.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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  • 75
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    Pulsational stabilities of a star in thermal imbalance - Comparison between the methods (1978)
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    Publication Date: 2011-08-17
    Description: The stability coefficients for quasi-adiabatic pulsations for a model in thermal imbalance are evaluated using the dynamical energy (DE) approach, the total (kinetic plus potential) energy (TE) approach, and the small amplitude (SA) approaches. From a comparison among the methods, it is found that there can exist two distinct stability coefficients under conditions of thermal imbalance as pointed out by Demaret. It is shown that both the TE approaches lead to one stability coefficient, while both the SA approaches lead to another coefficient. The coefficient obtained through the energy approaches is identified as the one which determines the stability of the velocity amplitudes. For a prenova model with a thin hydrogen-burning shell in thermal imbalance, several radial modes are found to be unstable both for radial displacements and for velocity amplitudes. However, a new kind of pulsational instability also appears, viz., while the radial displacements are unstable, the velocity amplitudes may be stabilized through the thermal imbalance terms.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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  • 76
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    The spectrum of HM Sagittae - A planetary nebula excited by a Wolf-Rayet Star (1978)
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 19; 3, 19; 1978
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  • 77
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    Enriched gas in clusters and the dynamics of galaxies and clusters Implications for theories of galaxy formation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Recent observations of the rotation of elliptical galaxies and of X-ray clusters are cited in developing a simple model for the formation of elliptical and spiral galaxies; the model provides for continuous galaxy formation from redshift values of about 100 onwards. In particular, it is argued that a fundamental alteration in the manner in which cosmic material fragmented to form stellar objects took place at a redshift value of approximately five. This change of regime may be employed to explain the formation of Population I disks, the origin of hot intracluster gas, the galaxy luminosity function, and the mass-to-light ratio stratification of galaxies.
    Keywords: ASTROPHYSICS
    Type: Comments on Modern Physics; vol. 7
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  • 78
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    A model of V356 Sagittarii (1978)
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    Publication Date: 2011-08-17
    Description: It is pointed out that V356 Sgr is an abnormal member of the Algol class of binaries. According to Popper (1955), the primary component is of spectral type B3V and is rotating rapidly, while the secondary is of type A2II and is rotating at least approximately in synchronism with the orbital motion. The system is either semidetached or quite near to being semidetached. The main anomalies are related to the ratio of eclipse depths, the very small reflection effect of the light curves, differences between the duration of the primary and the secondary eclipse, and the unusual characteristics of the primary eclipse. It is concluded that the lack of agreement between theory and observation can be due only to an important attribute of the binary which has not yet been incorporated into the theory. The peculiarities can most reasonably be explained in terms of a geometrically and optically thick disk which surrounds the primary component.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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  • 79
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    Energetic secondary electrons and the nonthermal galactic radio background - A probe of the magnetic field in interstellar clouds (1978)
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    Publication Date: 2011-08-17
    Description: A previous analysis of the manifestations of charged-pion-decay secondary electrons in interstellar cloud material is extended to include those contributions to the Galactic radio and soft gamma-ray backgrounds that are directly attributable to energetic secondaries. The equilibrium distribution of secondary electrons in dense interstellar clouds is calculated, synchrotron emissivity from isolated interstellar clouds is examined, and it is shown how the value of the magnetic field in these clouds may be determined by observing the radio emission in their directions. The contribution that such clouds make to the integrated radio background is evaluated, and the Galactic distribution of bremsstrahlung gamma rays that arise from interactions of secondary electrons with thermal material in dense clouds is computed. The results indicate that a magnetic field of no more than 80 microgauss is characteristic of dense clouds and that the integrated synchrotron radiation from secondary electrons in interstellar clouds will contribute a significant fraction of the nonthermal brightness along the Galactic equator even if the mean cloud field is as low as 35 microgauss.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
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  • 80
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    Acceleration of protons at 32 Jovian radii in the outer magnetosphere of Jupiter (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A rapid ten-fold increase of proton flux was observed at 32 Jovian radii in Jupiter's outer magnetosphere. The total event lasted about 30 minutes and was composed of many individual events. Both before and after the event, proton flux was similar to the low-flux level found between crossings of the magnetic equator. Measurements of angular distributions and the time histories of proton and alpha particle channels at different energies indicate that the flux increase is caused by local acceleration. It is suggested that the average particle population in the outer magnetosphere is caused by a state of dynamic equilibrium between acceleration and loss processes.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 83; Mar. 1
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  • 81
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    Partially averaged field approach to cosmic ray diffusion (1978)
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    Publication Date: 2011-08-17
    Description: A new nonlinear technique is used to derive the kinetic equation for particles interacting with turbulent fluctuations. Difficulties associated with quasi-linear theory are avoided. The new method evaluates the effects of the fluctuations along particle orbits which themselves include the effects of a statistically averaged subset of the possible configuration of the turbulence. As an illustration, the pitch-angle diffusion coefficient is calculated for particles interacting with 'slab model' magnetic turbulence, i.e., magnetic fluctuations linearly polarized transverse to a mean magnetic field. The pitch-angle diffusion coefficient is determined in the vicinity of 90-deg pitch angles where quasi-linear theory breaks down. The spatial diffusion coefficient parallel to a mean magnetic field is evaluated by use of the calculated pitch-angle diffusion coefficient. It is suggested that the partially averaged field method is not limited to small amplitude fluctuating fields and hence is not a perturbation theory.
    Keywords: SPACE RADIATION
    Type: Physics of Fluids; 21; Mar. 197
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  • 82
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    Baryon symmetric big bang cosmology (1978)
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    Publication Date: 2011-08-17
    Description: Both the quantum theory and Einsteins theory of special relativity lead to the supposition that matter and antimatter were produced in equal quantities during the big bang. It is noted that local matter/antimatter asymmetries may be reconciled with universal symmetry by assuming (1) a slight imbalance of matter over antimatter in the early universe, annihilation, and a subsequent remainder of matter; (2) localized regions of excess for one or the other type of matter as an initial condition; and (3) an extremely dense, high temperature state with zero net baryon number; i.e., matter/antimatter symmetry. Attention is given to the third assumption, which is the simplest and the most in keeping with current knowledge of the cosmos, especially as pertains the universality of 3 K background radiation. Mechanisms of galaxy formation are discussed, whereby matter and antimatter might have collided and annihilated each other, or have coexisted (and continue to coexist) at vast distances. It is pointed out that baryon symmetric big bang cosmology could probably be proved if an antinucleus could be detected in cosmic radiation.
    Keywords: ASTROPHYSICS
    Type: Nature; 273; June 15
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  • 83
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    Origin and evolution of the radio emission from immediate postoutburst supernovae (1978)
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    Publication Date: 2011-08-17
    Description: Several models for the radio emission from immediate postoutburst supernovae are examined under the assumption that the expanding remnant consists of a homogeneously mixed distribution of relativistic particles, magnetic field, and thermal plasma. The evolutionary models are: (1) an adiabatic expansion model; (2) a model incorporating the existence of a central pulsar; and (3) variations on the first two models in which relativistic electrons are accelerated either instantaneously or over an extended period of time and in which ionization, bremsstrahlung, synchrotron, Compton, and expansion losses are explicitly included. The character of the radio emission expected from these models is quite dissimilar. Whereas in adiabatic expansion models the emission is expected to increase slowly and become most intense at high frequencies, in models involving a central pulsar the emission should increase rapidly with a maximum flux density that is the same at all frequencies. The theoretical evolution of the radio emission for each model is compared with observations of SN 1970g.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 220
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  • 84
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    Nuclear brightness profiles of the X-ray globular cluster M15 compared to M3, M5, and M13 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Densitometer tracings of the globular clusters M3, M5, M13 and M15 indicate that the central peak of the brightness profile for M15 is narrower in the red than in the blue region. It is suggested that the red excess in the nucleus of M15 is due to red giants.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 83; May 1978
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  • 85
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    Maximum temperatures during the formation of the solar nebula (1978)
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    Publication Date: 2011-08-17
    Description: Most numerical models of cloud collapse yield the result that temperatures were never above 1000 K at distances not less than 1 AU from the axis of the forming solar system. In contrast, most meteorite researchers hold that higher temperatures are necessary to account for a variety of elemental fractionations found between groups of meteorites, between members of a single group, and between components of a single meteorite. A summary of the researchers' viewpoint is presented. An investigation is conducted of the evidence which indicates that chondrites were formed in the solar nebula. Attention is also given to the maximum nebular temperatures during the formation of chondrites.
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  • 86
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    The chaotic solar nebula - Evidence for episodic condensation in several distinct zones (1978)
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    Publication Date: 2011-08-17
    Description: Abundances of rare earth elements in Allende inclusions are considered along with the rim sequence on coarse-grained chondrules. It is found that in at least several zones the nebula went through episodes of condensation and gas/grain separation. Four separate zones are required to make the two types of fine-grained aggregates and the two types of coarse-grained chondrules. Other types of inclusions in Allende, such as the olivine aggregates, may well require additional condensation zones. All of these conclusions are based on data from one meteorite. Although the details of the gas/grain separation mechanism in these zones is not well understood, it is clear that a single monotonic-cooling condensation sequence followed by isolation of grains from gas cannot account for the observations.
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  • 87
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    Interplanetary dust - Possible implications for comets and presolar interstellar grains (1978)
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    Publication Date: 2011-08-17
    Description: Interplanetary dust is important to studies of the origin of the solar system because it is material from comets and asteroids, the smallest surviving bodies from the early solar system. The fact that comets are the major suppliers of the millimeter meteoroids which produce optical meteors suggests that a significant fraction of the submillimeter portion of the meteoroid complex is also cometary material. While comets are probably the major source, it is important to remember that the dust presently impacting the earth was probably generated by a number of different parent bodies. The collection of interplanetary dust is considered and a description is presented of the physical properties of interplanetary dust, taking into account the structure, elemental composition, and mineralogy.
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  • 88
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    Effect of the Mott cross section on the determination of the charge of ultraheavy cosmic rays from emulsion tracks (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Energy deposition due to secondary electrons is calculated as a function of distance from the axis of the track of a heavy ion. The calculation incorporates the empirical formulas of Kobetich and Katz (1968) for delta-ray energy dissipation. Both the Mott and Born-approximation expressions for the delta-ray energy distributions are used, and the results are compared. The energy deposition projected along a line perpendicular to the track is also calculated. These results are used to estimate the effect that the use of the Mott cross section would have in the interpretation of photometric measurements on emulsion tracks of trans-iron cosmic-ray particles. It is shown that the use of 50 keV as a characteristic track-formation electron energy to estimate the effect of the Mott cross section systematically overestimates charge as derived from emulsions for Z greater than 20.
    Keywords: SPACE RADIATION
    Type: Physical Review D - Particles and Fields; vol. 18
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  • 89
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    IMF structures between 0.3 and 1 A.U. - A comparison of two-spacecraft observations (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Interplanetary-magnetic-field observations by Helios 1 and IMP 8 have been compared for a period of time (corresponding to four solar rotations) in which the radial and latitudinal separations between spacecraft, respectively, ranged between 0 and 0.69 AU and 0 and 14.5 degrees. The correspondence between macrostructural features is good even when the observing spacecraft are located at opposite sides of the solar equatorial plane. Unipolar regions of the interplanetary magnetic field are confirmed as steady-state, corotating structures and are also mostly consistent with a quite regular extension of the field polarities of the observed coronal holes. There are, however, interesting examples of recurrent unipolar regions which are not associated with the recurrent pattern of high-velocity streams. A comparison of two field enhancements suggests that these structures do not experience significant modifications with the heliocentric distance.
    Keywords: ASTROPHYSICS
    Type: Nuovo Cimento C; vol. 1C
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  • 90
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    Neutron stars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Quantum-mechanical processes associated with the presence of high magnetic fields and the effect of such fields on the evolution of neutron stars are reviewed. A technical description of the interior of a neutron star is presented. The neutron star-pulsar relation is reviewed and consideration is given to supernovae explosions, flux conservation in neutron stars, gauge-invariant derivation of the equation of state for a strongly magnetized gas, neutron beta-decay, and the stability condition for a neutron star.
    Keywords: ASTROPHYSICS
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  • 91
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    X-ray emission from RS CVn systems - A progress report (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A report is given on progress made in a search for soft X-ray emission from RS CVn systems, using the low-energy detectors aboard HEAO 1. To date, nine systems have been seen. The properties of these systems are discussed. The failure to detect certain systems is considered. The possibility is discussed of discovering hitherto unknown RS CVn systems with soft X-ray observations.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 83; Dec. 197
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  • 92
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    Stellar winds and the evolution of luminous stars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The effect of a stellar wind on the evolution of stars in the mass range 7-60 solar masses has been investigated for stellar models in which Carson's opacities have been employed. Several cases of mass loss have been considered. It is found that the assumption of heavy mass loss from both blue and red supergiants can account well for the relevant observations of OBN stars, WN stars, and very luminous supergiants of all spectral types. But no amount of mass loss can account adequately for the properties of the B supergiants of lowest luminosity. A critical comparison is made between the present results and some earlier results based on the adoption of Cox-Stewart opacities.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 226
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  • 93
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    On the nature and origin of comets and their contribution to planets (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The rotation of cometary nuclei and certain properties of cometary ices are discussed. Observations show that comets were formed at extremely low temperatures and probably contain amorphous ices that give off exothermal energy on mild heating. While a large comet has a slow rotation period, many smaller typical comets appear to be rotating rapidly, indicating that encounters among them were frequent during formation. An estimate for the product of the relaxation time for encounters and the mean space density near the end of comet formation is presented, and a time scale of approximately 1,000,000 yr for comet accumulation is suggested. Some probable and possible contribution of comets to the solar system are summarized.
    Keywords: ASTROPHYSICS
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  • 94
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    IUE observations of the interstellar medium (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results from a preliminary study of interstellar absorption lines in the spectra of the three stars HD149757, HD93521 and HD153919, observed by the IUE during its commissioning phase are presented. They demonstrate the capabilities of the IUE for interstellar research. Results from a preliminary study of the emission line spectrum of the planetary nebula NGC 7027 are outlined and used to study its interstellar reddening.
    Keywords: ASTROPHYSICS
    Type: Nature; 275; Oct. 5
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  • 95
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    Gamma-ray astronomy and the origin of cosmic rays (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Recent observations of cosmic gamma radiation are reviewed. It is shown that this radiation consists of an extragalactic background as well as a bright band of galactic radiation lying in the plane of the Milky Way and produced primarily by cosmic-ray collisions with interstellar gas atoms. The galactic gamma radiation is divided into a near component apparently associated with Gould's belt and a far component originating about 15,000 light years away and narrowly confined to the galactic plane. A Great Galactic Ring is identified which is 35,000 light years in diameter and in which most galactic cosmic rays are produced and supernovae and pulsars are concentrated. The physical mechanisms responsible for the production of most of the cosmic gamma rays in the Galaxy are examined, and the origin of galactic cosmic rays is considered. It is concluded that the cosmic rays are produced either in supernova explosions or in the pulsars they leave behind
    Keywords: SPACE RADIATION
    Type: American Scientist; 66; Sept-Oct
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  • 96
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    A consistent age for the Universe (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The constraints associated with traditional dating methods for determining the age of the universe are combined in the context of the standard cosmological model to see which age can satisfy them all. The allowed age of the universe is found to range from 13.5 to 15.5 times 1,000,000,000 years in accordance with the limits for the density parameter being 0.06 and 0.3 and the limits for the heavy element mass fraction of globular clusters being 0.0001 and 0.001. The proposed range for the age of the universe agrees with Friedmann's description of the universe.
    Keywords: ASTROPHYSICS
    Type: Nature; 274; Aug. 17
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  • 97
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    The X-ray source Serpens X-1 - Ariel 5 observations and discussion of models for the spectrum and time variability (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Experimental data from Ariel 5 on the spectral shape and time variability of Ser X-1 are presented, and possible explanations for the observations are discussed in terms of current theoretical suggestions for source emission. The observations are summarized in the form of a light curve for 3-7.6-keV photons. The data are fitted with a power law of index -2.3, which yields a hydrogen column density of (1.1 + or - 0.4) x 10 to the 22nd power atoms/sq cm. No persistent periodicity of amplitude greater than 5% of the steady flux is found, but evidence of statistically significant burst activity is obtained. Various emission mechanisms are considered for the time-averaged spectrum and the X-ray bursts. It is suggested that the inverse Compton mechanism is a likely cause for the emission from this source and that the source is radiating near the Eddington limit.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 184
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  • 98
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    Detection of the C4H radical toward IRC plus 10216 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Four emission doublets in the millimeter-wave spectrum of IRC plus 10216 are identified as successive rotational transitions of the linear butadiynyl radical (C4H). The identifications are made on the basis of the agreement to within about 1 part in 1000 between the observed rotation constant of C4H and the value obtained from a Hartree-Fock calculation. A rough estimate of the amounts of C4H and C3N in the molecular envelope of IRC plus 10216 is given. The results indicate that C4H seems to be the more abundant species by about a factor of 4.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 224
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  • 99
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    The far-infrared spectrum of S140 IR (1978)
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    Publication Date: 2011-08-17
    Description: The spectrum of S140 IR from 65 to 345 kaysers (155-29 microns) has been measured with 9.4-kayser resolution. The emission in this spectral range is consistent with a 9-arcsec-diameter blackbody radiating at a temperature of 70 K. Attempts at finding a self-consistent radiative-transfer model of the source suggest that the near- and far-infrared observations cannot result from a spherically symmetric nebula with a continuous density distribution and a central exciting source. A number of compact near-infrared sources may be embedded in the cloud.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 224
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  • 100
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    On the stability of disklike galaxies in massive halos (1978)
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    Publication Date: 2011-08-17
    Description: Results are reported for a series of disk-galaxy simulations carried out as part of a systematic search for disk-galaxy models that show little change over the time of several galactic rotations. Systems in a given fixed external field, such as might be provided by a massive halo, are considered. The analysis is performed in terms of two parameters: the fraction of the total mass that resides in the active disk and the velocity dispersion in the active disk. The amount of halo mass required to stabilize a disk with a given velocity dispersion is investigated along with the question of whether any amount of halo mass can stabilize a completely 'cold' disk galaxy. The experimental results are quoted as growth rates estimated from plots of the amplitudes of Fourier analyses of the density in each of a set of narrow annuli, and systematic trends in the dependence of growth rates on the adjustable parameters are examined. It is shown that a massive inert halo contributes to the stability of disk-galaxy models, but some velocity dispersion is required.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 224
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