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  • ASTROPHYSICS  (2,155)
  • 1975-1979  (2,155)
  • 1
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    Precise determination of the distances of galaxies (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The use of the Space Telescope in the determination of the distances of galaxies is examined. The Space Telescope can check the local extragalactic distance scale to within 10-15 percent. The determination of relative distances of cosmic standard candles, viz. brightest M-supergiants and SNe I in E galaxies, is discussed. The M-supergiants map the velocity field out to v sub o approx. 3000 km s(-1) thus providing a firm basis for the determination of H sub o (global) from local distances, and the possibility to derive precise distances of all nearby field galaxies from their recession velocities. Photometry of the SNe I out to z = 0.5 leads to a direct determination of q sub o via the Hubble diagram, and the form of their light curves offers a fundamental test on the nature of redshifts. Other calculations are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 263-293
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  • 2
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    Requirements for predictions and real-time monitoring for the study of travelling interplanetary phenomena (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Physical processes within quiescent as well as disturbed flows of solar wind plasma, energetic particles, and magnetic and electric fields from the Sun are considered. Specifically, travelling interplanetary phenomena to be studied during the years of the solar maximum of solar cycle 21 are covered. It is noted that predictions, while needed for long range, logistical planning, is secondary to the requirements of synoptic real time monitoring over a wide range of particle energies and spectral bandwidths.
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 340-345
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  • 3
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    The problems of cosmology (1979)
    In:  CASI
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    Publication Date: 2006-01-16
    Description: Three examples that illustrate the expected role of the Space Telescope in cosmological investigations are described addressing the distribution of globular star clusters, universe expansion, and other classical cosmological problems.
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 295-312
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  • 4
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    The central regions of active galaxies and quasars (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Theories describing the central regions of nonthermal extragalactic sources (radio galaxies, Seyfert nuclei, quasars, etc.) are examined in the light of the experimental possibilities afforded by the Space Telescope. In particular, the theory which proposes the accretion of stars or gas onto a black hole as the explanation of the central engine is discussed. Planned observations directed towards the problem of the mass, size, and structure of the central engine, and the phenomenological questions regarding the general environment of the central engine are outlined.
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 197-214
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  • 5
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    Luminosity functions and evolution of globular clusters (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The stellar dynamics of globular clusters are addressed in terms of luminosity functions, chemical topics, and dynamical topics
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 139-150
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  • 6
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    The X-ray spectrum of 3C 273 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 7
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    Interstellar C2 molecules toward Zeta Persei (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A search for absorption by interstellar C2 molecules, conducted at the (2-0) Phillips band near 8760 A, is reported for three stars. No interstellar absorption is seen in the spectra of 20 Tau and Epsilon Aur, at upper limits of approximately 5 mA and 1 mA, respectively. Toward Zeta Per, however, the R(0), Q(2), and Q(4) lines are detected, and a useful upper limit on the Q(6) line is obtained. The resulting column density, 1.4 x 10 to the 13th to 2.0 x 10 to the 13th per sq cm, and the excitation temperature, T = (78 plus or minus 25) K, show acceptable agreement with an existing theoretical model of the absorbing cloud.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 8
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    Galaxies and gamma-ray astronomy (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The nature of the high-energy spectra of several types of active galaxies and their contribution to the measured diffuse gamma-ray emission between 1 and 150 MeV are considered, using X-ray spectra of active galaxies and SAS 2 data regarding the intensity upper limits to the gamma-ray emission above 35 MeV. It is found that a substantial increase in slope of the photon energy spectrum must occur in the low energy gamma-ray region for Seyfert galaxies, BL Lac objects, and emission line galaxies; the power-law spectra observed in the X-ray range must steepen substantially between 50 keV and 50 MeV. In addition, a cosmological integration shows that Seyfert galaxies, BL Lac objects, and quasars may account for most of the 1-150 MeV diffuse background, even without significant evolution.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 9
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    Magnetic Cepheids (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The role of a magnetic field in the pulsational behavior of classical Cepheids has been studied by computing linearized models of pulsating stellar envelopes pervaded by a well-tangled magnetic field. It is found that the 'pulsational' masses of Cepheids that are implied by the theoretical values of the quantities Q(0), P(1)/P(0), and (possibly) P(2)/P(0) can be brought into line with the large 'evolutionary' masses, if the pressure due to the postulated magnetic field is assumed to be comparable to the thermodynamic pressure everywhere in the pulsating layers. The field strengths that are required - several hundred gauss at the surface and several ten thousand gauss at the base - are quite reasonable from the point of view of the observed magnetic fields in Cepheids. The influence of the magnetic field on the location of the blue edge of the instability strip in the H-R diagram is estimated to be very slight.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 10
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    HEAO 1 observations of the X-ray pulsar 4U 1626-67 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for an observation of the 7-s pulsar 4U 1626-67 with the A-2 experiment on HEAO 1. The phase-averaged X-ray spectrum between 0.7 and 60 keV is complex, as are the constituent spectra, which change radically as a function of pulse phase. Included in this spectral change is the sudden appearance and subsequent decay of a continuum or emission feature with a mean energy of 19 keV, which contains about one-half the power in this spectral range. Pulse-timing results include a new determination of the pulse period and a factor of 8 reduction in the upper limit for the light travel time for orbital periods between 1 and 7 hours. These findings are discussed and compared with the general nature of pulsar spectra.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 231
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  • 11
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    Statistical equilibrium in cometary C2. II - Swan/Phillips band ratios (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Statistical equilibrium calculations have been made for both the triplet and ground state singlets for C2 in comets, using the exchange rate as a free parameter. The predictions of the results are consistent with optical observations and may be tested definitively by accurate observations of the Phillips and Swan band ratios. Comparison with the one reported observation indicates compatibility with a low exchange rate and resonance fluorescence statistical equilibrium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 231
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  • 12
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    Pioneer 10 studies of interplanetary shocks at large heliocentric distances (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Pioneer 10 Ames plasma analyzer data collected in the 6.1 to 12.6 AU range of heliocentric distances (November 1974 to April 1977) have been examined for interplanetary shock waves. Eighteen shock signatures have been identified, with four of these being of the reverse type and the remainder the forward type. Sonic Mach numbers in the range from 3 to 10 are estimated for these events.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters; 6; June 197
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  • 13
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    Discovery of two distorted interstellar bubbles (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: During an extensive program of direct imagery of emission nebulae, arcuate structures have been found around two stars. A well-defined shocklike structure is found about the T Orionis variable LL Ori, located to the side of the Orion Nebula. A less extensive shocklike structure is also found about the runaway star Zeta Oph. These structures can be best described in terms of distorted interstellar bubbles. A direct consequence of this interpretation is an independent estimate of the rates of mass loss for these stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 23
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  • 14
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    An upper limit for the total energy of relativistic particles contained in the early stages of supernova explosions (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A model is proposed for the emission of X-rays from supernova explosions wherein the thermal distribution of photons from a supernova photosphere is inverse Compton scattered by relativistic electrons within or near the surface of the star. Using this model, upper limits for the number of relativistic electrons and their total energy are established on the basis of upper limits to the observed X-ray luminosity of a supernova during maximum light. These upper limits, in conjunction with radio frequency upper limits obtained by Brown and Marscher, strongly suggest that supernovae do not produce significant numbers of relativistic particles until at least 70 years after the initial outburst. This, in turn, implies that young supernovae cannot account for the radio and X-ray variability of active galactic nuclei and quasars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 15
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    Gamma rays from accretion onto rotating black holes (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Ionized matter falling onto an isolated rotating black hole will be heated sufficiently that proton-proton collisions will produce mesons, including neutral pions, which decay into gamma rays. For massive (1000-solar mass) black holes, the resulting gamma-ray luminosity may exceed 10 to the 36th erg/s with a spectrum peaked near 20 MeV.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 74; 1, Ap; Apr. 197
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  • 16
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    Sporadic mass ejection in red supergiants (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A general mechanism first proposed by Burke (1969) is applied to red supergiants for determining the spin-down rate and angular-momentum loss of rotating stars. This model relies principally on sporadic mass ejection, which is assumed to be the result of turbulent elements accelerating material in cool supergiant atmospheres. Mass is preferentially expelled in the forward direction of rotation, resulting in a rapid loss of angular momentum on time scales of 10,000 to 1 million years in the supergiant evolutionary phase. Such rotational breaking will occur if the turbulent elements have characteristic sizes a few percent of the stellar radius and rms velocities one-third the escape speed of the star. This model predicts the formation of a cool silicate disk or torus around the star because of the preferred expulsion of material near equatorial regions of the supergiant.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 228
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  • 17
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    Absorption models for low-frequency variability in compact radio sources (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The consequences of the most plausible version of the absorption model for low-frequency variability in compact extragalactic radio sources are considered. The general restrictions placed on such a model are determined, and observational tests are suggested that can be used either to support the model or to discriminate among its various versions. It is shown that low-frequency variability in compact radio sources can be successfully explained by a class of models in which the flux is modulated by changes in free-free optical depth within an intervening ionized medium. Two versions of such a model are distinguished, one involving large changes in optical depth and the other, small changes. It is noted that while absorption effects are capable of causing rapid flux and structural variations at centimetric wavelengths, the models predict detailed behavior that is in direct conflict with observational data.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 228
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  • 18
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    Comptonization of X-rays by low-temperature electrons (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A method is described for calculating the spectrum that results from the Compton scattering of a monochromatic source of X-rays by low-temperature electrons, both for initial-value relaxation problems and for steady-state spatial diffusion problems. The method gives an exact solution of the inital-value problem for evolution of the spectrum in an infinite homogeneous medium if Klein-Nishina corrections to the Thomson cross section are neglected. This, together with approximate solutions for problems in which Klein-Nishina corrections are significant and/or spatial diffusion occurs, shows spectral structure near the original photon wavelength that may be used to infer physical conditions in cosmic X-ray sources. Explicit results, shown for examples of time relaxation in an infinite medium and spatial diffusion through a uniform sphere, are compared with results obtained by Monte Carlo calculations and by solving the appropriate Fokker-Planck equation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 228
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  • 19
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    Photoneutrino reactions in a superstrong magnetoactive plasma (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The neutrino luminosity due to the photoneutrino process in the presence of a superstrong magnetoactive electron plasma appropriate for neutron stars is computed. The results indicate that for relatively low temperatures, between 100 million and 500 million K, the energy loss rate is significantly reduced both in the low-density regime below about 10 million g/cu cm (by the magnetic field) and in the high-density regime above that value (by plasmon excitations). These effects are temperature dependent, and they are less pronounced when the temperature is in the range from 500 million to 1 billion K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 20
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    Detection of HC/O-18//plus/ in Sagittarius B2 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Line emission at 85.1 GHz attributed to the J equals 1-0 rotational transition of the formyl ion HC(O-18)(plus) has been detected in Sgr B2 (OH). The double isotopic ratio (O-16/O-18)/(C-12/C-13) in the formyl ion in Sgr B2 is estimated to be in the range 5-10, hence within a factor 2 of the terrestrial value of 5.5. This determination implies that the C-13/C-12 ratio near the galactic center does not differ greatly from that in local molecular clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 21
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    Galactic distribution models of gamma-ray burst sources (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The log N-log S relationships for several galactic distribution models of gamma-ray burst sources are derived. The resulting curves are substantially different from the galactic curves usually assumed (slope = -1). There is a relatively weak dependence on the radial distribution assumed but a strong dependence on scale height. Available observational data from several experiments appear to rule out both thin disk distributions and extended halo distributions which have a strong radial density dependence. The prospects are good for obtaining self-consistent distribution data from future large-area detectors.
    Keywords: ASTROPHYSICS
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  • 22
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    Scale covariance and G-varying cosmology. II - Thermodynamics, radiation, and the 3 K background (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Within the framework of a scale-covariant theory of gravitation, a semiclassical description of particles and photons is given. Thermodynamic relations consistent with the modified conservation equations are derived. Application to a system of radiation shows that the observed 3-K background radiation can be interpreted, within the present framework, as a remnant of equilibrium radiation in the past. As the theory postulates a nonstandard coupling between gravitation and electrodynamics, the assumption that Einstein's theory of gravitation is unchanged forces modifications at the atomic level. The use of Minkowskian spacetime in atomic physics is found to be adequate only over small, but not large, time scales compared with the age of the universe. As a result, a relation between energy and the frequency of a free photon is demonstrated. Possible observational consequences of this relation are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 41; Oct. 197
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  • 23
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    Large-scale structure of X-ray clusters of galaxies (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations from the A-2 experiment on HEAO-1 are used to search for very large-scale structure (exceeding a degree) in 40 X-ray sources in clusters of galaxies. Significant evidence for extension is found only in the relatively nearby Perseus and Virgo clusters. For the remainder of the sources the results place stringent limits on the flux in any very large component.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 189
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  • 24
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    The violent interstellar medium (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observational evidence for high-velocity and high-temperature interstellar gas is reviewed. The physical processes that characterize this gas are described, including the ionization and emissivity of coronal gas, the behavior and appearance of high-velocity shocks, and interfaces between coronal gas and cooler interstellar gas. Hydrodynamical models for the action of supernova explosions and stellar winds on the interstellar medium are examined, and recent attempts to synthesize all the processes considered into a global model for the interstellar medium are discussed.
    Keywords: ASTROPHYSICS
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  • 25
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    HEAO 1 observations of 4U1232+07 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An analysis of the NRL HEAO 1 observations of the Virgo cluster and 3C 273 has revealed X-ray emission from a region between these two objects. The most satisfactory explanation is the presence of two weak X-ray sources, for which error boxes have been obtained. One source is likely to be the peculiar galaxy IC 3576, suggested by Margon et al. (1972) as the source 2U 1231+07=4U 1232+07. The error box resulting from combining the present observations with the 4U data strengthen the X-ray identification with this extremely interesting galaxy. There are numerous possibilities for the other X-ray source, including the interacting pair of galaxies NGC 4410a and NGC 4410b (NGC 4410a/b).
    Keywords: ASTROPHYSICS
    Type: Nature; 281; Oct. 11
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  • 26
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    VV 5-32-63/64 - The 'supermassive double galaxy' in Abell 1775 revisited (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectroscopy is presented for galaxies in A 1775, the cluster containing VV 5-32-63/64, an apparent double galaxy which has long been considered a gravitationally bound system with supermassive components (10 to the 13th solar masses). However, this model has run afoul of recent radio observations, which detected an extremely long straight radio tail emanating from the eastern galaxy in the pair. The present observations indicate that if both galaxies are members of the same cluster, the cluster radial-velocity dispersion (1522 km/sec) is large enough to account for the velocity difference between the two VV galaxies (1650 km/sec). It is therefore suggested that the VV galaxies are not gravitationally bound and need not be supermassive. The large velocity dispersion measured for A 1775 also strains suggested velocity dispersion vs X-ray luminosity relations for clusters of galaxies, as A 1775 has not yet been detected at X-ray wavelengths.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 91
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  • 27
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    Infrared spectroscopy of stars (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper reviews applications of IR techniques in stellar classification, studies of stellar photospheres, elemental and isotopic abundances, and the nature of remnant and ejected matter in near-circumstellar regions. Qualitative IR spectral classification of cool and hot stars is discussed, along with IR spectra of peculiar composite star systems and of obscured stars, and IR characteristics of stellar populations. The use of IR spectroscopy in theoretical modeling of stellar atmospheres is examined, IR indicators of stellar atmospheric composition are described, and contributions of IR spectroscopy to the study of stellar recycling of interstellar matter are summarized. The future of IR astronomy is also considered.
    Keywords: ASTROPHYSICS
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  • 28
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    Observed properties of interstellar dust (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Recent information on the observed properties of interstellar dust is reviewed, with an attempt made to clarify some of the observational uncertainties associated with obtaining dust parameters. Attention is given to interstellar extinction, the interstellar dust distribution, the dust-to-gas ratio, and light scattering by dust grains. Interstellar polarization is also examined, along with heavy-element depletion in the interstellar medium, thermal emission from interstellar dust grains, diffuse interstellar features, and the composition and origin of interstellar grains.
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  • 29
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    Stellar magnetic fields - The role of a magnetic field in the peculiar M giant, HD 4174 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Principles of coronal heating via basic electrodynamic effects, viz., resonant absorption of Alfven surface waves (quiescent) and magnetic tearing instabilities (impulsive), are detailed to argue three principles which may have application to late-type evolved stars. First, if one observes that B-squared/8 pi is much greater than rho times v-squared in a stellar atmosphere, then the observed magnetic field must originate in an interior dynamo. Second, low mass-loss rates could imply the presence of closed magnetic flux loops within the outer atmosphere, which constrain hydrodynamic flows when the magnetic body forces exceed the driving forces. Third, given that such magnetic loops effect an enhancement of the local heating rate, a positive correlation is predicted between the existence of a corona and low mass-loss rates. Application of these principles is made in the case of the peculiar M giant star HD 4174, which is purported to have a kilogauss magnetic field. Several of its spectroscopic peculiarities are shown to be consistent with the above principles, and further observational checks are suggested. Possible application to dMe and RS CVn objects is sketched.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 91
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  • 30
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    Physical parameter profiles of selected X-ray flares (1979)
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    Publication Date: 2011-08-17
    Description: Soft X-ray proportional-counter data for nine X-ray flares of class C1 to M1 occurring during the Skylab mission, have been analyzed to yield temperature, volume emission measure, electron density and thermal energy content. Profiles of these quantities are presented, using 1-min averages of 2.5-s resolution data. The event profiles are discussed and comparisons with previous studies made.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series; 38; Oct. 197
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  • 31
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    Pulse-phase spectroscopy of Hercules X-1 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The 6-18 keV and the 40-60 keV X-ray spectrum of Hercules X-1 were simultaneously observed with the A-2 experiment on HEAO-1. By combining these measurements with the results of an earlier observation of this X-ray pulsar, evidence was found for a component of emission above 40 keV which is above an extrapolation from lower energies, by a factor which depends on the phase of the pulse. These data were compared to previous hard X-ray observations and possible models were discussed.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 188
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  • 32
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    Cosmic far-ultraviolet background radiation - Probe of a dense hot intergalactic medium (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Line and continuum radiation fluxes have been computed for a wide range of enriched intergalactic medium (IGM) models. Observations of the diffuse extragalactic light at optical and far-ultraviolet wavelengths are found to provide a potentially important probe of a dense hot intergalactic medium. If the diffuse X-ray background is produced by this gas, the models constrain the cosmological density parameter (Omega) to be less than 0.4. The associated Compton distortions of the cosmic blackbody background radiation and the optical depths to distant quasars at X-ray wavelengths are also evaluated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 231
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  • 33
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    Double core evolution and X-ray binaries (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The evolution of a 16-solar mass star and a 1-solar mass neutron star is followed through the common-envelope binary phase. It is found that the encounter of the neutron star with a yellow giant leads to coalescence of the two cores, while encounter with a red giant leads to hydrodynamic expansion and probable ejection of the common envelope. Within the context of the two rotation laws (1) uniform rotation (investigated in the present study), and (2) uniform specific angular momentum (considered in an earlier study), the results are independent of the choice for the angular-momentum distribution in the common envelope. Implications of the results for the binary pulsar phase are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 20; 2, 19; 1979
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  • 34
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    Reversal of the /O III/lambda 4363/H sub gamma lambda 4340 ratio in the planetary nebula IC 4997 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Five image-tube spectrograms of the planetary nebula IC 4997 obtained during August 1977 show that the intensity forbidden ratio O III 4363 A/H-gamma 4340 A was equal to unity, but a sixth one obtained in April 1978 showed the ratio to be 0.91. These results represent a significant increase in the intensity ratio, which had been declining from 1895 to 1962 (when it was considerably less than unity), and is interpreted as resulting from a gradual increase in temperature of the nebula's central star accompanied by a transient event which led to a temporarily high value for the ratio in mid-1977.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 231
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  • 35
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    X-ray observations of AM Herculis from OSO 8 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: X-ray observations of the white dwarf binary system AM Herculis in the range 2 to 250 keV, taken by OSO 8, are presented and compared with balloon and Ariel 5 measurements. The composite spectrum of the 2 to 40 and 20 to 250 keV fluxes determined by the proportional counter and the high energy scintillation spectrometer, respectively, on board the satellite is shown averaged over the entire binary cycle. Variations in spectral shape and intensity between the OSO 8 results and balloon measurements taken 10 to 20 days apart are observed. Results indicate the presence of a spectral break at about 15 keV on some occasions, similar to that seen in Her X-1, however presumably caused by a different mechanism than in the neutron star. It is also considered unlikely that the gamma-ray tail observed by Ariel 5 existed during OSO 8 observations.
    Keywords: ASTROPHYSICS
    Type: Nature; 279; June 7
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  • 36
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    NGC 1275 /3C 84/ - Similar structure in the optical and 3-mm radio variations (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Optical and 3.3-mm data for the Seyfert galaxy NGC 1275 (3C 84) are compared. Similarities exist between the variations at the two wavelengths with regard to amplitude, time scale, and interval between events. The question is raised whether these similarities may be the result of a common triggering mechanism.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 91
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  • 37
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    An analysis of the infrared continuum of comets. II - Comet Kohoutek (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An analysis of the infrared observations of comet Kohoutek has been carried out on the basis of silicate grain models. The 'observed' grain temperature has been obtained as a function of the heliocentric distance, and it is compared with the expected distribution. In the visible region, one requires for the refractive index, (m = n-ik), n of about 1.6 and k less than 0.05. The total number of grains varies essentially as the inverse square of radial distance; the size of the particles in the antitail of the comet Kohoutek is greater than 5 microns. The ratio of infrared flux from grains to the incident solar flux at wavelengths of a few microns is calculated.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 84; May 1979
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  • 38
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    Cool stars - Effective temperatures, angular diameters, and reddening determined from 1-5 micron flux curves and model atmospheres (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 228
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  • 39
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    Some simple properties of stellar pulsation modes (1979)
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    Publication Date: 2011-08-17
    Description: Except for the lowest harmonics, small-amplitude stellar pulsation modes possess many simple properties whose evaluation does not require numerical integration of the fourth-order equations of motion. All antinodes tend to have the same total kinetic energy except for those lying near physical or geometric boundaries. However, when kinetic energy per unit volume is considered, order-of-magnitude enhancements are seen in antinodes lying near the center of the star, and factor-of-2 enhancements occur near the polar axis. The nodes are distributed very regularly along the radius. They follow an exponential law in g-regions, and their separation is proportional to the sound travel time in p-regions. A simple graphical procedure is described for surveying the oscillation frequencies of a new stellar model. A precise condition is derived giving the division of energy between radial and angular motion. Another condition gives the fractional contribution to the velocity field of its two sources, the divergence and the curl. Certain simplifying results of weak coupling among the linear modes are briefly described.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 40
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    Theories of magnetospheres around accreting compact objects (1979)
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    Publication Date: 2011-08-17
    Description: The paper reviews theoretical models of magnetospheres formed around neutron stars and other strongly magnetized compact objects in the presence of mass accretion from a companion star. Emphasis is placed on the interaction of the accretion process with the magnetic field of the compact object and the formation of a magnetosphere. The following models are discussed: magnetospheres with polar funnels; closed magnetospheres and their instabilities; models of internal flow; and disk accretion magnetospheres.
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  • 41
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    The discovery of 38.22 second X-ray pulsations from the vicinity of OAO 1653-40 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A 38.22-s X-ray pulsator has been discovered during an 8-hour HEAO 1 pointed observation of the area of sky containing OAO 1653-40. It is found that this pulsing source is not associated with V861 Sco, the proposed optical identification for OAO 1653-40. The spectrum is very hard, the spectral index being about 1.4, with about a 500-eV equivalent width of iron-line emission. No high-energy cutoff is observed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 42
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    Scale covariance and G-varying cosmology. IV - The log N-log S relation (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The traditional radio counts N(S) and radio source models are studied within the framework of the scale-covariant cosmology developed to investigate whether the relative strength of the gravitational and electromagnetic constants is a function of cosmological epoch. It is found that a gravitational constant G varying as the inverse of t, where t is the epoch in atomic units, is consistent with all the data analyzed. For a wide class of models the present cosmology allows a finer discrimination of the deceleration parameter than does standard theory. The results, when combined with those of previous papers, namely, those from radio and optical flux and angular-diameter data analysis, favor an open universe.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 41; Oct. 197
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  • 43
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    Infrared methane spectra between 1120 per cm and 1800 per cm - A new atlas (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A new atlas of CH4 lines in the 1120-1800-per cm region has been generated, based on laboratory spectra taken with a Nicolet interferometer at 0.06-per cm resolution with 635-cm path length at pressures of 0.98 torr, 4.86 torr, and 19.97 torr. A compilation of line positions and line intensities includes 1339 CH4 lines, several hundred of which have not been previously observed.
    Keywords: ASTROPHYSICS
    Type: Applied Optics; 18; Nov. 15
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  • 44
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    Radio emission from nova shells (1979)
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    Publication Date: 2011-08-17
    Description: This paper presents data from multifrequency radio observations of the novae HR Del 1967 and FH Ser 1970 made from June 1970 to December 1978 and of V1500 Cyg 1975 made from September 1975 to December 1978. The data for FH Ser and V1500 Cyg constitute a complete history of the important phases of their radio 'light' curves, while all but the rising portion of the optically thick phase of an expanding nova shell is present for HR Del. A simple solution of the spherically symmetric equations of mass and momentum conservation for an isothermal gas, for which pressure gradients are effectively decoupled from the dynamics, is shown to fit the radio data for all three novae quite well. The main features of this model are strong density and velocity gradients that lead to long periods when the 'observable' shell evolves from an optically thick 'disk' to a completely optically thin shell.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 84; Oct. 197
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  • 45
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    Search for X-ray emission from bursting radio sources (1979)
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    Publication Date: 2011-08-17
    Description: Results are reported for a systematic search with the A-2 experiment aboard HEAO 1 for X-ray emission from 28 radio sources that were actually bursting at the epoch of the X-ray observations. Two of these sources are found to lie within the positional errors of X-ray sources: the moderately redshifted quasars NRAO 140 and NRAO 530. The positions of 30 historically variable radio sources that were not active at the time of the search are compared with those of detectable X-ray sources, but no X-ray emission is detected from any of these positions. The implications of the results are discussed in terms of models for the radio emission from compact extragalactic sources. Several possible explanations are presented for the general absence of Compton X-ray emission from the bursting radio sources surveyed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 46
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    Long-term studies with the Ariel 5 ASM. II - The strong Cygnus sources (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The three bright 3-6 keV X-ray sources in Cygnus are examined for regular temporal variability with a 1300 day record from the Ariel 5 All-Sky Monitor. The only periods consistently observed are 5.6 days for Cyg X-1, 11.23 days for Cyg X-2, and 4.8 hours for Cyg X-3. The 78.4 day period of Kemp, Herman, and Barbour for Cyg X-1, the 9.843 day period of Cowley, Crampton, and Hutchings for Cyg X-2, and the 16.75 day period of Holt et al. for Cyg X-3 are not confirmed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 47
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    Thermonuclear runaways on neutron stars (1979)
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    Publication Date: 2011-08-17
    Description: Thermonuclear runaways which develop when neutron stars of 0.476 solar masses accrete hydrogen-rich material at 10 to the -10th and 2 x 10 to the -9th solar masses/year have been followed using a numerical model. It is found that a thermal instability occurs at densities in excess of 10 to the 5th g/cu cm and that the maximum accumulated mass required to initiate the runaway is 0.7 x 10 to the -12th and 2.1 x 10 to the -12th solar masses for the mass accretion rates of 10 to the -10th and 2 x 10 to the -9th solar masses/year, respectively. Heating the of the neutron star envelope by hydrogen burning leads to the ignition of helium. The nonequilibrium burning of helium by a combination of (alpha, p), (p, gamma), and (alpha, gamma) reactions involving O-14, O-15, and other heavy nuclei provides the energy for an X-ray burst. The gross properties of these models bear suggestive resemblance to those observed for some X-ray burst sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 48
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    Intense interplanetary magnetic fields observed by geocentric spacecraft during 1963-1975 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In the present paper, interplanetary magnetic field and plasma data are reviewed over a period exceeding one full solar cycle for intervals in which the magnetic intensity was greater than 13 gammas. One hundred forty nine intervals of this type, with almost complete plasma and magnetic field data, are identified. Most (79%) of these enhancements could be associated either with interplanetary shocks or with high-speed stream interfaces. Half of the remaining 21% of the enhancements could be identified as cold magnetic enhancements, while the other half could not be associated with a single shock, interface, or cold magnetic enhancement.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 49
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    The shape and location of the sector boundary surface in the inner solar system (1979)
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    Publication Date: 2011-08-17
    Description: Simultaneous observations by Helios 1 and Helios 2 over four solar rotations, between January 20 and May 23, 1976, were used to determine the latitudinal dependence of the polarity of the interplanetary magnetic field within plus or minus 7.23 deg of the solar equator and within 1 AU. The longitudinal and latitudinal positions of the sector boundary crossing are consistent with a warped sector boundary which extended from the sun to 1 AU and was inclined approximately 10 deg with respect to the heliographic equator. This is consistent with simultaneous Pioneer 11 observations, which showed unipolar fields at approximately 16 deg latitude at heliocentric distances greater than 3.5 AU. Two sectors were observed at southern latitudes; however, four sectors were observed at northern latitudes on two rotations, indicating a distortion from planarity of the sector boundary surface.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 50
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    The dynamics and stability of radiatively driven gas clouds. I - Plane-parallel slabs (1979)
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    Publication Date: 2011-08-17
    Description: A combination of numerical and analytical techniques has been used to investigate the dynamics and stability of optically thin plane-parallel radiatively driven slabs of gas confined by the thermal gas pressure of a high-temperature low-density medium. Scaling laws allow the individual model 'clouds' to be characterized by a single free parameter, chi, a normalized column density which measures the strength of the acceleration due to radiation pressure relative to that due to thermal gas pressure. It is found that these clouds are stable and coherently accelerated only when chi is small. In this regime a simple slab model is constructed which accurately reproduces the more complex gasdynamic results. The low-chi clouds are marginally able to reach the high velocities seen in the atmospheres of quasi-stellar objects, but only if their motion is subsonic with respect to the external confining medium. This implies either that the medium is extremely hot and tenuous or that it is moving outward with the clouds.
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  • 51
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    Scale covariance and G-varying cosmology. III - The /m, z/, /theta sub m, z/, /theta sub i, z/, and /N/m/, m/ tests (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Einstein gravitational equations in atomic units are fully solved for a matter-dominated universe in the context of a recently proposed scale-covariant cosmology. The magnitude-redshift relation for elliptical galaxies is studied, the evolutionary parameter used in such a study is derived, and the relation between isophotal angular diameters and redshifts is investigated, along with the relation between metric angular diameters and redshifts, the N(m)-magnitude relation for QSOs, and the magnitude-redshift relation for QSOs. Results are presented for four gauges (i.e., relations between G and the scale function beta (t)), and no contradictions are found between the proposed theory and the observational data. It is shown that only an open universe can fit the data if certain gauges suggested by a recent analysis of the time variation of the moon's period are selected and that observations made with atomic instruments do not necessarily yield geometrical parameters unless specific assumptions are made regarding the relation between atomic and gravitational dynamics.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 41; Oct. 197
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  • 52
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    Theoretical aspects of coherent radio-emissions in nature - The pulsar example (1979)
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    Publication Date: 2011-08-17
    Description: Some general considerations on natural radio emissions in the solar system are presented with emphasis on coherence of emissions and turbulence effects. This is followed by a review of theoretical mechanisms of pulsar radio emission.
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  • 53
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    A search for X-ray bursts from extragalactic supernovae using the HEAO 1 satellite (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The soft X-ray data from the low energy detectors of the HEAO 1 A-2 experiment are surveyed in the 0.15-3.0 keV range to search for X-ray bursts (less than 1 hour) from extragalactic supernovae predicted by Klein and Chevalier. To within the operating sensitivity of 0.08 photons per sq cm/s no events were discovered from the first 8 months of operation. This is consistent with the theoretical prediction that the probability of finding one such event is small. The HEAO 2 satellite should be capable of detecting supernovae out to 2000 Mpc; these events are of cosmological interest.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 54
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    Observations of Cygnus X-3 above 50 keV (1979)
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    Publication Date: 2011-08-17
    Description: Cygnus X-3 was observed in the energy range 50-400 keV using a balloon-borne, actively collimated, NaI(Tl) scintillation detector. The observation was made from phase 0.45-0.91 of the 4.8 hour period. The photon number spectrum was well represented by a power law with index -2.2. The flux increased throughout the observation, consistent with a highly asymmetric light curve with a peak near phase 0.9.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 55
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    Interplanetary gas. XXIV - Are cometary plasma tail disconnections caused by sector boundary crossings or by encounters with high-speed streams (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper discusses and compares the original sector boundary model (Niedner and Brandt) and the alternative high-speed stream model (Ip and Mendis) suggested for explaining cometary plasma tail disconnection events (DE) within a largely observational framework not dependent on detailed plasma physics. Among the findings are: (1) the strong solar cycle phase dependence of the amplitude of the Rosenberg-Coleman effect (Svalgaard and Wilcox) yields inferred maximum latitudes of all of the DEs in the original survey to a one-time Rosenberg-Coleman effect measurement made by Pioneer 11, which indicated a disappearance of sectors above 16 deg latitude, and (2) approximately 70% of the post 1926 DEs in the expanded survey show a close association with corotated shorter-term polarity reversals. This result is difficult to reconcile with the predictions of the stream model, in which DEs should correlate more strongly with streams than with sector boundaries. It is concluded that the sector boundary model better describes the disconnection phenomenon and that the use of DEs as unique sector boundary markers is presently justified.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 56
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    High energy X-ray observations of Sco-like sources with Ariel V (1979)
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    Publication Date: 2011-08-17
    Description: Results are reported for observations of Sco X-1 and the similar sources 4U 1702-36 (GX 349+2, Sco X-2), 4U 1813-14 (GX 17+2), and 4U 1758-25 (GX 5-1) by several of the X-ray telescopes aboard the Ariel 5 satellite over the energy range from 2 to approximately 100 keV. The results confirm the existence of a high-energy tail in the spectrum of Sco X-1, demonstrate that 4U 1702-36 has a similar spectrum, and provide evidence for a variation of the 26-56-keV flux from 4U 1702-36 by more than a factor of four with no related change in the 2.9-7.6-keV flux. The high-energy emission from Sco X-1 is found to be one to two orders of magnitude above the extrapolated low-energy emission. Observed X-ray, radio, and optical properties of these four sources, as well as two additional Sco-like sources, are summarized.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 189
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  • 57
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    An extended investigation of Helios 1 and 2 observations - The interplanetary magnetic field between 0.3 and 1 AU (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Helios 1 and 2 spacecraft allowed a detailed investigation of the radial dependence of the interplanetary magnetic field components between 0.3 and 1 AU. The behavior of the radial component is in a very good agreement with Parker's model (approximately equal to the inverse square of the heliocentric distance) and the azimuthal component also shows a radial dependence which is close to theoretical predictions (approximately equal to the inverse of the heliocentric distance). Experimental results for the normal component and for the field magnitude are consistent with those from previous investigations. The relative amplitude of the directional fluctuations with periods less than 12 hr is essentially independent of heliocentric distance, while their power decreases approximately as the inverse cube of the heliocentric distance without any appreciable difference between higher and lower velocity regimes.
    Keywords: ASTROPHYSICS
    Type: Solar Physics; 63; Sept
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  • 58
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    Some aspects of condensation in clouds (1979)
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    Publication Date: 2011-08-17
    Description: Several general features of nucleation characteristics of low-density cosmic clouds are discussed. These are: (1) tendency for metastable condensates to form; (2) nonoccurrence of nominal refractory molecules in the gas; (3) a strong temperature dependence of condensation at relatively low temperatures; and (4) significant vibrational disequilibrium in cosmic clouds. These support previous analyses which indicate that equilibrium calculations have restricted applicability. A kinetic treatment of condensation is required for cosmic grains, and the possibility of formulating such an analysis is pointed out.
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    Laboratory simulation of infrared astrophysical features (1979)
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    Publication Date: 2011-08-17
    Description: Laboratory infrared emission and absorption spectra have been taken of terrestrial silicates, meteorites, and lunar soils in the form of micrometer and submicrometer grains. The emission spectra were taken in a way that imitates telescopic observations. The purpose was to see which materials best simulate the 10-micron astrophysical feature. The emission spectra of dunite, fayalite, and Allende give a good fit to the 10-micron broadband emission feature of comets Bennett and Kohoutek. A study of the effect of grain size on the presence of the 10-micron emission feature of dunite shows that for particles larger than 37 microns no feature is seen. The emission spectrum of the Murray meteorite, a Type 2 carbonaceous chrondrite, is quite similar to the intermediate-resolution spectrum of comet Kohoutek in the 10-micron region. Hydrous silicates or amorphous magnesium silicates in combination with high-temperature condensates, such as olivine or anorthite, would yield spectra that match the intermediate-resolution spectrum of comet Kohoutek in the 10-micron region. Glassy olivine and glassy anorthite in approximately equal proportions would also give a spectrum that is a good fit to the cometary 10-micron feature.
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  • 60
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    X-ray evidence for electron-ion equilibrium and ionization nonequilibrium in Young supernova remnants (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: X-ray emission up to 25 keV from the supernova remnants Cas A and Tycho has been detected with the A-2 spectroscopy experiment on HEAO 1. The spectra must include continuum components with effective temperature of about 10 to the 8th K which could arise from optically thin plasmas in the collisionless shock fronts. This is the first indication of electron-ion temperature equilibrium in the expanding shell of young remnants. The equivalent widths of the K-alpha and K-beta iron line blends in Cas A have also been measured and it is found that their ratio is not compatible with the measured X-ray temperature in the collisional ionization equilibrium model. Finally, an unsuccessful search has been conducted for hard X-ray pulsars in both remnants.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 61
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    Collective radio-emission from plasmas (1979)
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    Publication Date: 2011-08-17
    Description: Collective radiation processes operating in laboratory and space plasmas are reviewed with an emphasis towards astrophysical applications. Particular stress is placed on the physics involved in the various processes rather than in the detailed derivation of the formulas. Radiation processes from stable non-thermal, weakly turbulent and strongly turbulent magnetized and unmagnetized plasmas are discussed. The general theoretical ideas involved in amplification processes such as stimulated scattering are presented along with their application to free electron and plasma lasers. Direct radio-emission of electromagnetic waves by linear instabilities driven by beams or velocity anisotropies are shown to be of relevance in space applications. Finally, as an example of the computational state of the art pertaining to plasma radiation, a study of the type III solar radio bursts is presented.
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  • 62
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    IUE observations of 32 Cygni - The effects of the B star within the upper chromosphere of a late-type supergiant (1979)
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    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 63
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    Evidence for variability of hard X-rays from NGC 4151 (1979)
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    Details
    Publication Date: 2011-08-17
    Description: A search for gamma-rays in the 35-keV to 8.7-MeV energy range from the Seyfert galaxy NGC 4151 was made using an actively collimated scintillation detector. Upper limits to the flux in the 100-200-keV energy range are inconsistent with previous observations. Variability on a time scale of several months is indicated. Implications in terms of current models of NGC 4151 are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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    Cool regions in relativistic plasmas - Thermal instabilities (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The thermal stability of a plasma consisting of dynamically dominant relativistic electrons and a warm inertial gas is studied. Bremsstrahlung, Coulomb, synchrotron, and inverse Compton losses are considered; it is found that plasmas in which the cooling is dominated by either of the first two processes are generally unstable, while synchrotron losses may or may not cause instability and inverse Compton losses are stabilizing. Characteristic growth times and unstable scales are determined from linear analysis. Applications of this instability to quasar atmospheres and to extended radio galaxies are discussed briefly.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 65
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    High energy X-ray observations of BL Lacertae objects (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Several BL Lacertae objects were observed at energies above 25 keV using the scintillation telescopes on OSO-8 and Ariel-5. With the possible exception of Markaryan 421, only upper limits were obtained for the existence of X-ray emission in the energy ranges 25-60 and 60-130 keV. These results impose constraints on any flattening in the X-ray spectrum of BL Lac objects as predicted by at least one model for their X-ray emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 20; 3, 19; 1979
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  • 66
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    Ultraviolet photometry with the Astronomical Netherlands Satellite /ANS/ Observations of Beta Canis Majoris variables (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper deals with detailed ANS observations of three Beta Canis Majoris variables: Xi-1 CMa, HD 61068 (whose discovery is reported here) and 15 CMa. Light curves at five ultraviolet wavelengths are presented, and the periods and amplitudes are discussed. The ultraviolet colors are used to derive temperatures and temperature variations, which are compared with the MK spectral types. The anomalously high luminosity found for Xi-1 CMa on the basis of certain line strengths is also discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 79; 1-2,; Oct. 197
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  • 67
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    Interstellar isothiocyanic acid (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Isothiocyanic acid (HNCS) has been identified in Sgr B2 from millimeter-wave spectral line observations. We have definitely detected three rotational lines, and have probably detected two others. The rotational temperature of HNCS in Sgr B2 is 14 plus or minus 5 K, its column density is 2.5 plus or minus 1.0 x 10 to the 13th per sq cm, and its abundance relative to HNCO is consistent with the cosmic S/O ratio, 1/42.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 68
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    Stellar evolution at high mass including the effect of a stellar wind (1979)
    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 from 15 to 120 solar masses is investigated. All the stellar models are constructed with the use of Cox-Stewart opacities. Four possible cases of mass loss are considered: (1) no mass loss at all; (2) substantial mass loss from stars in all stages of evolution; (3) heavy mass loss from red supergiants only; and (4) sudden and very heavy mass loss from luminous yellow supergiants. The assumption of mass loss during the main-sequence phase of evolution is found to lead to a lowering of the luminosity and, unless the mass loss is extremely heavy, of the effective temperature as well. A comparison of the adopted mass-loss rates with observed rates suggests that stellar winds are probably not an important factor in the evolution of main-sequence stars and supergiants unless the initial masses are greater than about 30 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 69
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    Interstellar methyl mercaptan (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Methyl mercaptan (CH3SH) has been identified in Sgr B2 from observations of six lines in its millimeter-wave spectrum. The CH3SH rotational temperature and column density in Sgr B2 are T(rot) = 9 plus or minus 3 K and N = 1.5 plus or minus 0.2 x 10 to the 14th per sq cm, respectively. The CH3SH/CH3OH ratio is apparently not greatly different from the cosmic S/O ratio.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 70
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    X-ray spectrum of Cassiopeia A measured with the Einstein SSS (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The solid state spectrometer (SSS) on the Einstein Observatory observed the X-ray spectrum of Cas A between 0.8 and 4.5 keV with a FWHM energy resolution of 160 eV. Line emission consistent with transitions of helium-like ions of Si, S, and Ar was well defined. Comparison between the data and the emission expected from a gas containing two distinct thermal components requires additional line emission from Mg, Al, Ca, and Fe. These results are discussed in the context of both equilibrium and nonequilibrium situations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 71
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    X-ray line emission from Capella (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: X-ray emission-line components from Mg, Si, S, and Fe are unambiguously detected from Capella with the solid-state spectrometer onboard the Einstein Observatory. The X-ray spectrum is inconsistent with an isothermal corona, and requires components between 6-million K and at least 24-million K for an adequate fit. An inhomogeneous corona in which the X-ray emitting plasma is confined to magnetically contained loops appears to be reconcilable with all of the experimental evidence.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 72
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    A limit to the X-ray luminosity of nearby normal galaxies (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The hypothesis that normal galaxies are on the average more luminous in the X-ray region than the Milky Way galaxy or M31 and therefore are possible candidates for the low-luminosity sources of the 2 to 60 keV extragalactic diffuse background is tested. Data from the A-2 detectors on the HEAO-1 spacecraft were examined for emission from positions coincident with 76 selected normal galaxies, and upper limits to the average galactic luminosity for various luminosity distributions resulting in the observed count rate distribution were determined. For uniform and exponential galactic luminosity distributions, limits of 2.7 x 10 to the 38th erg/sec and 3.4 x 10 to the 38th erg/sec, respectively, at the 90% confidence level were obtained. It is shown that the Hubble-constant-independent upper limit to galactic emissivity is less than 1% of the diffuse background emissivity, indicating that normal galaxies are not responsible for the diffuse X-ray background and have luminosities comparable to that of the Galaxy.
    Keywords: ASTROPHYSICS
    Type: Nature; 281; Sept. 13
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  • 73
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    The linear X-ray polarization of Scorpius X-1 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Scorpius X-1 was observed with the Bragg crystal polarimeters aboard OSO 8 in August 1977 and again in August 1978. An analysis of these observations reveals a time-averaged polarization of 0.39% plus or minus 0.20% at 2.6 keV and 1.31% plus or minus 0.40% at 5.2 keV. The corresponding position angles are 29 deg plus or minus 10 deg and 57 deg plus or minus 6 deg, respectively. Binary phase-dependent polarization was searched for but not observed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 74
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    Carbon and nitrogen abundances in red giant stars in the globular cluster 47 Tucanae (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The effects of changes in temperature, gravity, overall metal abundance, and carbon and nitrogen abundances have been investigated for model stellar spectra and colors representing globular-cluster giants of moderate metal deficiency. The results are presented in the form of spectral atlases and theoretical color-color diagrams. Using these results, approximate abundances of carbon and nitrogen have been derived for some red giant stars in 47 Tuc, from intermediate- and low-dispersion spectra and from intermediate- and narrow-band photometry. In all the normal giants studied, nitrogen is overabundant by up to about a factor of 5 (the precise value depends on the adopted carbon abundance), with different enhancements for different giants. The observational material is not sufficient to distinguish between a normal carbon abundance and a slight carbon depletion for the giant-branch stars, but carbon appears to be somewhat depleted in stars on the asymptotic giant branch. A most probable value of M/H = -0.8 for the overall cluster metal abundance is suggested from analysis of Stromgren photometry of red horizontal-branch stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 75
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    A change in the X-ray spectrum of Markarian 421 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: HEAO 1 A-2 experiment observations of the BL Lacertae object Mrk 421 in May 1978 show a marked spectral change from the OSO 8 observations of May 1977. The source was not detected above 10 keV in May 1978. The 2-10 keV spectrum could be well fitted by a power law with an energy slope of 2.2 to 4.2; thermal bremsstrahlung models with T less than 20 million are also acceptable. There was no indication of any low-energy turnover, so that the inferred column density is less than 7 x 10 to the 21st H atoms per sq cm. The total flux is consistent with an extrapolation of the UV data from IUE, but the slope is not consistent with the UV slope. Possible models for the origin of the spectral transition are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 76
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    Gamma-ray burst observations from Helios 2 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of five gamma-ray bursts made with the solar orbiter Helios 2 are reported. Wavefront timing from Helios 2, at distances of up to 1.98 AU, to Vela 5A and 6A, in earth orbit, provides source location bands as narrow as 2 arcmin, although several degrees in length. The burst intensities and time profiles measured in interplanetary space by Helios 2 are the same as those observed near the earth, ruling out a narrow-beam interplanetary origin model. Also, the source direction bands for these events are inconsistent with the directions of all known celestial X-ray objects, X-ray bursters, and high-energy gamma-ray source regions. The gamma-ray burst source objects therefore appear to form a class distinct from all lower-energy X-ray or higher energy gamma-ray emitters.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 77
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    An upper limit on ultraviolet shot noise from Cygnus X-1 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Rapid photometry of Cygnus X-1 through an ultraviolet filter centered on 0.35 micron has been obtained at 100-ms sampling intervals. The autocorrelation function of these data has been examined for shot noise analogous to the behavior of the X-ray light curve. The ultraviolet data are entirely consistent with white noise. Considering randomly occurring ultraviolet shots with the same duration (0.5 s) and average rate (1 per sec) as the X-ray shots, a 3-sigma upper limit on the ratio of optical to X-ray energies per shot is estimated to be 0.13, before the ultraviolet light is attenuated by interstellar dust. This limit is then generalized for shots of arbitrary duration and rate.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 78
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    Theory of the intercluster medium (1979)
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    Publication Date: 2011-08-17
    Description: A set of computer models for the evolution of intercluster matter (ICM) in expanding cosmologies which includes processes of electron impact ionization/excitation, radiative and dielectronic recombination, thermal bremsstrahlung, Compton scattering, and photoionization is presented. The thermal, ionization, and excitation histories of major constituents were found as functions of time, and predictions of emission spectra, the possible distortions of the cosmic 3 K microwave background, and optical depths of absorption troughs in QSO continua at various redshifts were obtained. It is concluded that the present Friedmann cosmology can be dominated by hot intercluster matter which would contain H and He in their cosmic ratio and traces of heavier elements. For a narrow range of parameters it is possible to generate cosmologies with a closure density of ICM which do not exceed the diffuse X-ray measurements. In open cosmologies distortion of the 3 K microwave background occurs, while closed cases show negligible change from the unperturbed spectrum.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 79
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    Varying G (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The problem of the variation of the gravitational constant with cosmological time is critically analyzed. Since Einstein's equation does not allow G to vary on any time scale, no observational data can be analyzed within the context of the standard theory. The recently proposed scale covariant theory, which allows (but does not demand) G to vary, and which has been shown to have passed several standard cosmological tests, is employed to discuss some recent nonnull observational results which indicate a time variation of G.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 188
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  • 80
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    New hard X-ray sources observed with HEAO A-2 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A search for new hard X-ray sources using data from the first complete view of the sky with the HEAO A-2 experiment has discovered 47 new sources, detected seven sources recently discovered with other experiments, and significantly reduced the size of the error boxes for six previously known sources. Intensities and error boxes are given for each of these sources; identifications are suggested when an error box contains an object similar to known X-ray sources. The new identifications consist of seven type 1 Seyfert galaxies, including two whose Seyfert characteristics were discovered as a result of their location in an X-ray error box; one intermediate Seyfert galaxy; three Abell clusters; five N galaxies; two bursting radio sources; and an additional three nearby galaxies with bright nuclei and narrow emission lines.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 40; July 197
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  • 81
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    Soft X-ray emission from the vicinity of MV Lyr (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Evidence for a soft X-ray source at the location of the nova-like variable star MV Lyr is presented. Data from the smallest field of view of the A2 experiment on board HEAO-1 in the range 0.18 to 2.5 keV reveals a source of 0.18 to 0.43 keV emission, designated H1901+43, with a count rate corresponding to a flux of 4 x 10 to the -12th erg/sq cm per sec if a spectral temperature of 3 x 10 to the 5th K is assumed. The two-dimensional error box of H1901+43 is observed to contain the UX UMa star MV Lyr, which is suggested as the only obvious candidate for the source of X-ray emission, in accordance with the observations of soft X-ray emission from other cataclysmic variables, notably AM Her, U Gem and SS Cyg.
    Keywords: ASTROPHYSICS
    Type: Nature; 280; Aug. 16
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  • 82
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    The interstellar oxygen edge in the X-ray spectrum of the Crab Nebula (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Measurement of the X-ray spectrum of the Crab Nebula by the HEAO 1 A-2 low-energy (0.15-3 keV) detectors is reported. The spectral restoration techniques described by Blissett and Cruise (1979) and Kahn and Blissett (1979) are used to demonstrate explicitly the existence of a 'negative' feature near 0.5 keV that is consistent with the edge expected due to absorption by interstellar oxygen. For a simple power-law model with photon index -2.08, the data require a column density of 3.0 + or - 0.1 x 10 to the 21st per sq cm and an oxygen abundance of 1.0 + or - 0.1 times the Brown and Gould (1970) value. Satisfactory fits can also be achieved with the more sophisticated Fireman (1974) models, but no model can be adjusted to fit the data without the inclusion of interstellar oxygen.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 83
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    Balloon-borne ultraviolet stellar spectrograph. I - Instrumentation and observation. II - Highlights of first observational results (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A dual star-tracking system and a system including a telescope, an echelle spectrograph, and a SEC vidicon are the chief components of the Balloon-borne Ultraviolet Stellar Spectrograph (BUSS), which has flown four successful missions. The BUSS missions have yielded 81 spectra for 56 stars, recorded with a resolution of 0.1 A in the wavelength range from 2200 to 3400 A. BUSS observations include: profiles of Mg II lines indicating considerable mass flow in early-type supergiants; Mg II features suggesting a cool expanding outer shell above a hotter chromosphere; emission features in Zeta Tau (a shell star) indicating infalling material; and emission features of the Be star Phi Per suggesting mass outflow.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 84
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    High-energy X-ray spectra of Cygnus XR-1 observed from OSO 8 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer aboard the OSO 8 satellite during a period of one-and-one-half to three weeks in each of the years from 1975 to 1977. Typical spectra of the source between 15 and 250 keV are presented and the spectra are found to be well represented by a single power-law expression whose photon number spectral index is different for the two intensity states that were considered. The observed pivoting effect is consistent with two-temperature accretion disk models of the X-ray emitting region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 85
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    Mass flow in close binaries - Results of optical and ultraviolet observations (1979)
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    Publication Date: 2011-08-17
    Description: Observational data provide information regarding mass flow in close binaries. Data about origin, condition, and development of circumstellar matter can also be obtained. The investigations are based on an evaluation and correlation of photometric observations and simultaneously made photoelectric and spectrographic observations in the visible spectral range and, in addition, also on satellite observations in the ultraviolet range. Supplementary information concerning the mass flow in close binaries is obtained on the basis of observations related to the X-ray, infrared, and radio range. Suitable theoretical models are employed to interpret the observational data.
    Keywords: ASTROPHYSICS
    Type: Sterne und Weltraum; 18; Feb. 197
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  • 86
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    The orbital period of Algol - 1964 to 1978 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A photoelectric observation of minimum light for Algol is reported: JD 2443565.5785 (visual) and JD 2443565.5802 (blue). The times of minima obtained between 1964 and 1978 indicate that a period decrease may have occurred about 1975. It is suggested that this period change, as well as the radio and X-ray activity and spectroscopic anomalies observed during 1975, may have been due to a mass-transfer event that occurred around that time.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 90
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  • 87
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    Starspots as the cause of the intrinsic light variations in RS Canum Venaticorum type stars (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A starspot model is proposed to interpret the light curves of three RS CVn type binary systems. Two of the systems are RS CVn and SZ Psc, which are detached, while the third system, RT Lac, is semidetached. Solar activity and the surface activity of the RS CVn type stars are compared. It is found that the spot model permits the detailed fitting of both the out-of-eclipse complications and the distorted shapes of the secondary eclipses in the light curves of these stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 88
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    Analysis of the helium component of the local interstellar medium (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of the extraterrestrial He I 584-A emission made with an EUV experiment aboard OSO 8 are analyzed and compared with previous data from a similar experiment aboard the STP 72 1 satellite. The observations are also compared with an exhaustive set of emission models, and an envelope of possible velocities and temperatures is defined for the local interstellar medium. This envelope begins near 9 km/s with temperatures of 6000 to 8000 K, continues upward through 15 km/s with temperatures of 6000 to 15,000 K, and finally terminates near 27 km/s with temperatures of 11,000 to 14,000 K; the densities corresponding to these velocities and temperatures cover the range from 0.008 to 0.02 per cu cm. Previous observations of hydrogen L-alpha emission from the interstellar wind are reviewed and compared with the 584-A observations. With a typical value of 12% assumed for the cosmic helium abundance, the present observations imply a hydrogen density of 0.067 to 0.17 per cu cm, in good agreement with the values obtained from the L-alpha measurements.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 89
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    On the formation and confinement of dense clouds in QSOs and active galactic nuclei (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A model for the formation and confinement of dense (at least about 1 billion per cu cm) clouds in QSOs and active galactic nuclei is presented wherein thermal instabilities behind radiative shocks cause the collapse of regions where the preshock density is enhanced over that of the surrounding medium. Such shocks (of total energy around 10 to the 51st ergs) are likely to occur if the frequent optical outbursts observed in many of these objects are accompanied by mass ejections of comparable energy. It is found that clouds quite similar to those thought to exist in QSOs etc. can be created in this manner at radii of the order of 10 to the 17th cm. The clouds can be subsequently accelerated to observed bulk velocities by either radiation pressure or a collision with a much stronger (total energy around 10 to the 53 ergs) shock. Alternatively, their high observed velocities could be caused by gravitational infall or rotation. The mass production required at inner radii by the outflow models can be supplied through a mechanism previously discussed by Shields (1977).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 90
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    Stark broadening of Fe I 5383 A (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for a laboratory measurement of the electron broadening of the Fe I line at 5383 A as a function of electron density over the temperature range from 8000 to 12,000 K. A linear Z-pinch electrical discharge served as the spectroscopic light source in the experiment, and special precautions were taken to allow for optical-depth effects, which have been a major source of error in previous investigations. The results obtained include a Stark-broadening constant of 0.106 + or - 0.004 x 10 to the -16th A-cu cm at a mean temperature of 9500 K, an estimated Stark width/electron-broadened width ratio of 1.09 + or - 0.02, and a normalized electron-broadened width of 0.097 + or - 0.004 x 10 to the 16th A-cu cm. Comparison of the last result with a calculated value and with a previous measurement indicates that the present measurement is approximately 38% larger than the value measured earlier.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 71; 3, Ja; Jan. 197
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  • 91
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    Long-term studies with the Ariel 5 ASM. I - Hercules X-1, Vela X-1, and Centaurus X-3 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1, and Cen X-3 accumulated with the Ariel 5 All-Sky Monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the 35 day variation of Her X-1, for which we can refine the period to 34.875 plus or minus 0.030 days. No such longer-term periodicity less than 200 days is observed from Vela X-1. The 26.6 days low-state recurrence period for Cen X-3 is not observed, but a 43.0 day candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 92
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    Two new methanol transitions in Orion A (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Emission from the 11(1) - 10(2) (A-) and 5(0) - 4(1) (E) transitions of CH3OH at rest frequencies of 76,247.4 and 76,509.9 MHz, respectively, has been detected toward Orion A. The velocity widths of the two transitions are estimated to be approximately 3 km/s, which is consistent with other methanol lines in Orion. It is noted that the 117.5-kayser upper-state energy of the 11(1) - 10(2) (A-) transition is the highest yet reported for methanol in any source. The observed intensity is shown to be consistent with the 90-K thermal excitation model that seems to be appropriate for all other reported CH3OH lines in Orion A. Total column densities of 3 x 10 to the 16th per sq cm for the 11(1) - 10(2) (A-) transition and of 2 x 10 to the 16th per sq cm for the 5(0) - 4(1) (E) transition are calculated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 93
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    Semiconvection and period changes in RR Lyrae stars (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The possibility is considered that convective mixing inherently associated with composition redistribution inward through a semiconvective zone (SCZ) and into the convective core by the end of the horizontal-branch (HB) phase may be primarily responsible for the observed period changes in RR Lyrae stars. Specifically, it is proposed that the period changes in RR Lyrae stars are caused mainly by small random mixing events within the SCZ and at the edge of the convective core. Tests of several HB models that include semiconvection are presented which demonstrate that stellar evolution cannot satisfactorily account for the observed period changes but that mixing events involving only a very small part of the SCZ or a very small extension of the convective core are sufficient to change the pulsation period of an RR Lyrae star by the amount typically observed. The frequency of the period changes is predicted theoretically and found to be in good agreement with the observed value within the substantial uncertainties involved. A procedure is outlined for future period-change testing of HB models.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 71; 1-2,; Jan. 197
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  • 94
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    Interstellar extinction and ultraviolet flux distribution of Scorpius X-1 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Measurements of absorption at 2200 A for Sco X-1 indicate an E(B-V) of approximately 0.28. The distance to Sco X-1 is estimated to be 350 pc while the X-ray luminosity is thought to be 5 times 10 to the 36th ergs/sec. It is found that the de-reddened ultraviolet flux distribution closely resembles a blackbody at 26,000 K. Brightness variations and their relation to flickering phenomena are considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 95
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    OSO 8 X-ray spectra of clusters of galaxies. II - Discussion (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An observational description of X-ray clusters of galaxies is given based on OSO 8 X-ray results for spatially integrated spectra of 20 such clusters and various correlations obtained from these results. It is found from a correlation between temperature and velocity dispersion that the X-ray core radius should be less than the galaxy core radius or, alternatively, that the polytropic index is about 1.1 for most of the 20 clusters. Analysis of a correlation between temperature and emission integral yields evidence that more massive clusters accumulate a larger fraction of their mass as intracluster gas. Galaxy densities and optical morphology, as they correlate with X-ray properties, are reexamined for indications as to how mass injection by galaxies affects the density structure of the gas. The physical arguments used to derive iron abundances from observed equivalent widths of iron line features in X-ray spectra are critically evaluated, and the associated uncertainties in abundances derived in this manner are estimated to be quite large.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 96
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    Cosmology of a charged universe (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3-K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
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  • 97
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    ESO 103-G35 - A new Seyfert galaxy and possible X-ray source (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: By means of an objective prism plate, two emission-line galaxies have been identified within the 0.7-sq deg HEAO-A2 error box for the X-ray source H1834-653. Optical spectrophotometric observations are reported for both objects as well as the galaxy NGC 6684, which also lies near the position of H1834-653. These data show that one of the emission-line galaxies, ESO 103-G35, is a Seyfert galaxy with a high-excitation forbidden-line spectrum and weak broad emission wings at H-alpha. Further measurements of this galaxy reveal an infrared excess at wavelengths longer than 2.2 microns. The H-alpha luminosity of ESO 103-G35 is consistent with the X-ray luminosity estimated from the HEAO-A2 data, thus strengthening the likelihood of association of this galaxy with the X-ray emission.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 76; 3, Ju; July 197
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  • 98
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    The 78.4-day period of Cygnus XR-1 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Data from observations of Cyg XR-1 made by the high energy X-ray spectrometer on OSO 8 were analyzed together with previously reported (Dolan, 1977) observations of the polarization of HDE226868 in the U-band in an attempt to detect the 78.8-d modulation reported by Kemp et al. (1977, 1978) in the optical and low-energy X-ray wavelength region. No such modulation was found at the wavelengths studied. It is suggested that if such modulation does exist, it is more likely to be related to the rotation of the free modes of oscillation of the primary than to the existence of a third body in the system.
    Keywords: ASTROPHYSICS
    Type: Nature; 280; July 12
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  • 99
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    Cosmological baryon-number domain structure from symmetry breaking in grand unified field theories (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It is suggested that grand unified field theories with spontaneous symmetry breaking in the very early big bang can lead more naturally to a baryon-symmetric cosmology with a domain structure than to a totally baryon-asymmetric cosmology. The symmetry is broken in a randomized manner in causally independent domains, favoring neither a baryon nor an antibaryon excess on a universal scale. Arguments in favor of this cosmology and observational tests are discussed.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 43; July 23
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  • 100
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    A comparison of emission lines in the ultraviolet spectra of Alpha Boo /K2IIIp/, Alpha Tau /K5III/, Alpha Ori /M1-2Ia-b/ and Alpha Sco /M1.5Iab+B2.5V/ (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series; 36; June 197
    Format: text
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