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  • Weitere Quellen  (733)
  • ASTROPHYSICS  (566)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE  (167)
  • 1980-1984  (733)
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  • 1
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    Use of multiblade sensors for on-line rotor tip-path plane estimation (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Techniques are investigated for on-line estimation of rotor states in the nonrotating frame from multiple, simultaneous measurements in the rotating frame. The multiblade coordinate transformation is first applied to transform both flapping and flapping rate measurements into the nonrotating frame. The 'observer' approach is then used to generate algorithms for estimating tip-path plane rate and attitude from transformed flapping and flapping rate measurements. A numerical evaluation using simulated measurements is conducted to evaluate the performance of the algorithms and recommendations are made.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: American Helicopter Society; vol. 25
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  • 2
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    The effect of rotation on the hydrodynamics of stellar collapse (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): ASTROPHYSICS
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  • 3
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    Fragmentation in rotating isothermal protostellar clouds (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper reports results of an extensive set of three-dimensional hydrodynamic calculations performed to investigate the susceptibility of rotating clouds to gravitational fragmentation; only isothermal collapse sequences were considered. It is found that rotating isothermal gas clouds are unstable to fragmentation under a wide range of conditions. The degree of instability and the mode (ring vs. blob) of fragmentation is sensitive to alpha, but insensitive to beta. The initial amplitude of a perturbation does not appear to be crucial; fragmentation should occur eventually even for low-amplitude initial NAPs.
    Schlagwort(e): ASTROPHYSICS
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  • 4
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    Spectroscopic and polarimetric observations of NGC 1333 and the surrounding dark cloud complex (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Spectroscopy and polarimetry of several very red stars, noted on Near Infrared Photographic Sky Survey photographs in the region of NGC 1333, have yielded a 'map' suggesting the extent of polarization arising from a two-cloud structure in the region. Spectral types and color indices of the stars make it possible to infer that grain radii in the clouds exceed typical interstellar medium values and, further, that they increase with optical depth into the cloud. The present observations indicate that the cloud structure is far more extensive than previously realized.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Journal; 85; Dec. 198
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  • 5
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    Collapse and equilibrium of rotating, adiabatic clouds (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A numerical hydrodynamics computer code analysis of the collapse and establishment of equilibrium of adiabatic gas clouds restricted to axial symmetry found that the clouds are originally uniform in density and rotation. The method can compare the dynamic collapse and approach to equilibrium with the data on incompressible uniformly rotating equilibrium clouds and on equilibrium structures of differentially rotating polytropes. It is concluded that the stellar formation theory indicates that the low alpha fragments produced at the termination of the dynamic isothermal collapse phase of interstellar clouds may undergo significant dynamic collapse in an adiabatic regime leading to transitory ring formation and additional fragmentation on a smaller scale.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 242
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  • 6
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    Comparisons of interstellar CH/+/ and H2 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Copernicus observations of H2 toward stars in the Pleiades and 23 Orionis have been obtained because of their importance in understanding the formation of interstellar CH(+). No model of CH(+) equilibrium seems to agree very well with these observations; in particular, the suggestions that CH(+) is formed either from collisions between vibrationally excited H2 and C(+) or from radiative association of C(+) and H2 can apparently be excluded. These data do suggest that there is a correlation between the amounts of rotationally excited H2 and CH(+) which are present. Observations of the Pleiades also help interpretations of the reflection nebulae near these stars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 242
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  • 7
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    Axial rotation, tangled magnetic fields, and theoretical models of very massive stars (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A simple method of computing theoretical models of very massive stars endowed with fast axial rotation and tangled magnetic fields is described and used in the present paper. Both of the two perturbing (nongravitational) forces induce changes in the luminosity and radius that are studied as functions of zero-age chemical composition, opacity, and evolutionary state of the interior. The central condensation of the star is found to have a significant influence on shifts of the upper main-sequence band in the H-R diagram if the perturbing force is concentrated in the stellar envelope (but not if the perturbing force is distributed so as to be approximately proportional to gravity everywhere); the layers of the envelope that contribute most heavily to the central condensation lie approximately at a radius fraction of r/R = 0.5. It is shown that fast uniform rotation and intense envelope magnetic fields lead to probably the largest possible shifts of the main-sequence band in the H-R diagram that rotation and magnetic fields can induce. These displacements are, however, too small to account for the total width of the observed main-sequence band at luminosities brighter than log (L/solar luminosity) = 4.5.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 242
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  • 8
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    The evolution of supernova remnants in different galactic environments and its effects on supernova statistics (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is shown that only a small fraction of the many supernovae in the Galaxy produces observable supernova remnants; this fraction, which is found to depend weakly on the lower mass limit of the SN progenitors, and more strongly on the specific characteristics of the associated interstellar medium, decreases from about 15% near the galactic center to 10% at R(gal) of about 10 kpc and drops nearly to zero for R(gal) greater than 15 kpc. Whether an SNR is detectable is determined by the density of the ambient interstellar medium in which it is embedded; it is found that SNRs are detectable only above some critical density (about 0.1 per cu cm). The presence of large low-density superbubble cavities around stellar associations due to the combined effects of stellar winds and supernova shells strongly suggests that a large portion of the detectable SNRs must have runaway stars as their progenitors.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 242
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  • 9
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    The unique cosmic event of 1979 March 5 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The transient gamma-ray burst observed on March 5, 1979 by the nine spacecraft forming the interplanetary gamma-ray burst network is discussed. Measurements reveal the event to be unlike any previously observed gamma-ray burst or X-ray burster, with a maximum intensity greater than several thousandths erg/sq cm per sec, a rise time of less than 200 microsec, a narrow and featureless initial spike and a regular 8-sec oscillation with a compound pulse shape. The source of the transient has been localized to a region including the supernova remnant N 49 in the Large Magellanic Cloud, at a distance of 55 pc, and a ratio of X-ray point-source steady state to transient emission of less than 10 to the -9th was obtained. The identification of the burst source with the supernova remnant at that distance would require an enormous source output if it was radiated isotropically, and substantially less if beaming is present. Alternatively, the event could be explained by a nearby, invisible neutron star.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Comments on Modern Physics; vol. 9
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  • 10
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    On the phase-locked polarization variations in Cygnus X-1 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper presents data on the accumulated V-band orbital phase curves of polarization in Cygnus X-1 which disagree with the analysis of Simmons, Aspin, and Brown (1980). No curves which conform to the canonical model were observed, and a noncanonical structure is indicated by F tests on third, fourth, and fifth harmonics, which have a probability of 0.85 as a group. The fifth harmonic has a probability of 0.99; in contrast, the fundamental harmonic has a probability of only 0.6, which is below the detection threshold. Therefore, major conclusions of Simmons et al based on a nonsymmetrical canonical model assuming that fundamental harmonics are present, but harmonics with n greater than 2 are absent, are unacceptable. Analysis of the author's data by Simmons et al is criticized on the grounds that he did not take into account the cumulative aspects of the data and did not recognize the need to average out the random noise generated by Cygnus X-1 over many orbital cycles.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 91; 1-2,; Nov. 198
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  • 11
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    The X-ray structure of two rich galaxy clusters and its implications for the detectability of microwave diminutions (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The X-ray observations of the galaxy clusters Abell 2319 and 576 show a reduced temperature of the microwave background due to the Suniaev-Zeldovich effect. The X-ray maps indicate smooth emission in these clusters concentrated toward the optical center; the surface brightness in the 1-3 keV band falls with the inverse square of radius outside a small core, and fits the Hubble's law of optical surface brightness of elliptical galaxies. The low temperature indicates that in A576 (1) the core radius of the gravitational potential is two to three times larger than inferred from galaxy counts, (2) the temperature rises with radius over most of the cluster and falls to zero at large radii, and (3) the gas does not obey the equation of state.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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  • 12
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    Radial accretion of H-rich material onto a He white dwarf (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The nova outburst is modeled by spherically accreting H-rich material onto a 1 solar mass He white dwarf at a rate of 10 to the -8th solar mass/yr. The star accretes for 5848 years, when the nuclear reactions run away near the base of the accreted envelope. The nuclear-energy generation rate rises to 4.6(8) solar luminosities, and the envelope expands in response to it. However, nova-like mass ejection does not occur because the envelope is of insufficient mass, the base of the envelope is only mildly electron degenerate, and there is no enrichment of the CNO abundance. To overcome these limiting conditions, it is suggested that the H-rich material be accreted either more slowly than 10 to the -10th solar mass/yr or with angular momentum. Outbursts resulting in the former case should be similar to the nova models computed by Starrfield, Truran, and Sparks. Outbursts in the latter case should be strengthened, and novae might result because the H-rich material will be mixed into the surface layers of the white dwarf, as first suggested by Kippenhahn and Thomas (1978).
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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  • 13
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    Spontaneous formation of knots in relativistic flows - A model for variability in compact synchrotron sources (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: A model is proposed in which regions of enhanced synchrotron emission are formed via radiative thermal instabilities in relativistic flows. A perturbed volume in which the magnetic field is enhanced by a few tens of a percent relative to the steady value collapses due to the increased cooling rate and consequent loss in pressure. The collapse further increases the magnetic field, leading to even shorter radiative lifetimes. The instability progresses in this way until either the external electron pressure is balanced by the perturbed magnetic pressure or the overall expansion of the flow becomes important. A fluid-dynamical treatment of the instability is performed, and the results are shown to apply to flux variations and formation of knots in the relativistic flows which are thought to occur in quasars and active galactic nuclei. The knots possess the same kinematic properties as the collimated flow and can thus be responsible for the apparent superluminal motions observed in compact radio sources.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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  • 14
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    Binary model of Circinus X-1. I - Eccentricity from combined X-ray and radio observations (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: A binary star model is used to account for the 16.59-d flaring behavior of the X-ray emission from Circinus X-1. The orbital eccentricity of 0.8 + or - 0.1 is derived from the X-ray light curve by assuming that the sharp X-ray cut-off every 16.59-d is a result of bound-free absorption in the primary star's stellar wind. The shape of the light curve has changed over the last eight years, and this is interpreted as due to orbital precession of the binary system. Simultaneous radio and X-ray observations of the flare from Circinus X-1 on February 1-5, 1978 are reported. These are accounted for within the framework of the model. The radio observations at 5 GHz are used independently to derive a high value of the orbital eccentricity (e = 0.7).
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 86; 3, Ju; July 198
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  • 15
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    IUE observations of the atmospheric eclipsing binary system Zeta Aurigae (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: IUE observations of the eclipsing binary system Zeta Aurigae made prior to and during the eclipse of the relatively small B8 V star by the cool supergiant star (spectral type K2 II) are reported. Spectral lines produced by the absorption of B star radiation in the atmosphere of the K star during eclipse can be used as a probe of the extended K star atmosphere, due to the negligible cool star continuum in the 1200-3200 A region. Spectra taken prior to eclipse are found to be similar to those of the single B8 V star 64 Ori, with the exception of very strong multi-component absorption lines of Si II, Si IV, C IV and the Mg resonance doublet with strong P Cygni profiles, indicating a double shell. Absorption lines including those corresponding to Al II, Al III, Cr II, Mn II, Fe II, Ni II and Ca II are observed to increase in strength and number as the eclipse progresses, with high-ionization-potential lines formed far from the K star, possibly in a shock wave, and low-ionization potential lines, formed in cool plasma, probably a cool wind, nearer to the K star. Finally, an emission-line spectra with lines corresponding to those previously observed in absorption is noted at the time the B-star continuum had disappeared.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 286; Aug. 7
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  • 16
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    The high-energy X-ray spectrum of Scorpius X-1 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 17
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    Quasi-stellar objects in the intergalactic medium - Source for the cosmic X-ray background (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Current estimates of QSO luminosity, number density, evolution, and spectral index are used to study whether the diffuse cosmic ray background is (1) entirely due to thermal bremmstrahlung of the intergalactic medium (IGM), (2) completely supplied by QSO X-rays, or (3) a combination of both. The upper limits on an IGM fractional density with respect to closure are Omega = 0.26, 0.24, and 0.21 for pure collisional, photo/collisional, and pure photoionization, respectively. These calculations give emission spectra, Compton distortion of the microwave background, and optical depths to distant QSOs for comparison with relevant data.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 18
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    A model of comet comae. II - Effects of solar photodissociative ionization (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Improvements to a computer model of coma photochemistry are described. These include an expansion of the chemical reactions network and new rate constants that have been measured only recently. Photolytic reactions of additional molecules are incorporated, and photolytic branching ratios are treated in far greater detail than previously. A total of 25 photodissociative ionization (PDI) reactions are now considered (as compared to only 3 PDI reactions previously). Solar PDI of the mother molecule CO2 is shown to compete effectively with photoionization of CO in the production of observed CO(+). The CO(+) density peak predicted by the improved model, for CO2 or CO mother molecules, is deep in the inner coma, in better agreement with observation than the old CO2 model. However, neither CO2 nor CO mother molecule calculations reproduce the CO(+)/H2O(+) ratio observed in comet Kohoutek. PDI products of CO2, CO, CH4, and NH3 mother molecules fuel a complex chemistry scheme, producing inner coma abundances of CN, C2, and C3 much greater than previously calculated.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 19
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    Laser spectroscopy of the CN radical and astrophysical applications (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The formation of CN radicals by flash photolysis of a number of parent molecules was monitored by laser induced fluorescence in the B2Sigma(plus)-X2Sigma(plus) transition of CN. The rotational and vibrational energy of the newly formed radicals in the X state was measured directly. Formation of CN(A2Pi) in the lower vibrational levels was determined by an indirect method based on resonant energy transfer to higher vibrational levels of the ground state. These laboratory studies have shown that high initial internal excitation of CN with rotational levels of maximum N equals 50-70 is the rule. In general, the formation of simple molecules in excited states is commonly the case. There appear to be astrophysical systems where radiation from these excited levels may be detectable. Such observations would serve as a probe of molecular formation.
    Schlagwort(e): ASTROPHYSICS
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  • 20
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    The spectrum of IRC + 10216 from 2.0 to 8.5 microns (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Low-resolution spectra of IRC + 10216 have been obtained from 2 to 8.5 microns from NASA's Kuiper Airborne Observatory at an altitude of 12.5 km (41,000 feet). Observations were made during 1976 January and 1977 February. In both sets of data, the spectral flux reaches its maximum between 6.0 and 6.6 microns and the previously reported 3.1-micron feature is observed; no obvious new absorption features have been found. The new data together with other spectral data and measurements of the spatial extent of IRC + 10216 impose conditions that must be met by models of the continuum. Several simple models for 2-8.5 micron radiation are examined. The new continuum data impose a constraint on the size of the grains in the cooler, optically thin part of the object. Earlier photometry has been combined with the present data to yield an improved value of the average period: 644 + or - 17 days. It appears that the variability is irregular and that the minima have been deeper in recent years than they were in 1965-1969.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 21
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    Self-gravitating gas flow in barred spiral galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: A series of two-dimensional numerical experiments is performed in order to test the response of an isothermal, self-gravitating gas disk to a uniformly rotating, barlike gravitational potential. The barlike potential is an equilibrium stellar model from the n-body calculations of Miller and Smith (1979). In the bar-dominated, central regions of the disk, a gas bar whose phase depends primarily on the location of principal resonances in the disk is formed. This response can be understood in terms of orbit-crowding effects. In the gas-dominated outer regions of the disk, two-armed trailing spiral waves are formed. The local pitch angle of these waves increases with increasing fractional gas mass. These self-gravitating gas waves are not self-sustaining. They are driven from the ends of equilibrium stellar bars, and their phase does not depend on the location of resonances in the disk. The relevance of these self-gravitating waves to observations and models of barred spiral galaxies is discussed. It is concluded that these waves and their associated ringlike structures may be consistent with the morphological distribution of gas features in barred spiral galaxies.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 22
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    Optical surface brightnesses of dusty galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: It is suggested that Freeman's (1970) result that the disk portions of spiral galaxies have a preferred central surface brightness might be the consequence of observing optically thick ensembles of a standard mix of stars and dust. Regardless of whether this hypothesis is correct, the observation that elliptical galaxies usually have central surface brightnesses considerably greater than the disk portions of spirals can be understood if there is much less dust within the elliptical systems. In particular, ellipticals probably have dust-to-total-mass ratios at least a factor of 100 smaller than in the disk portions of spirals, although there is no evidence that the dust-to-interstellar-gas ratios are different. When stars were forming within ellipticals, these galaxies were probably dustier than they are now, and their visible light output could have been substantially affected. It will probably be necessary to establish the dust content of galaxies as a function of redshift to use these objects as cosmological probes.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 23
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    New spectroscopic constants for methane derived by using microwave transitions from the interstellar medium (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Schlagwort(e): ASTROPHYSICS
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  • 24
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    Comment on the paper 'A cosmological limit on the possible variation of G' (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society; vol. 191
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  • 25
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    The promise of multicyclic control (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The rough ride a helicopter endures is known to be self-generated. This roughness results in fatiguing blade loads and vibration which can be eliminated or greatly reduced by multicyclic control. Rotor performance may also be improved. Several types of rotors which have employed multicyclic control are reviewed and compared. Their differences are highlighted and their potential advantages and disadvantages are discussed. The flow field these rotors must operate in is discussed, and it is shown that simultaneous elimination of vibration and oscillatory blade loads is not an inherent solution to the roughness problem. The use of rotor blades and energy absorbers is proposed. Input-output relations are considered and a gain control for ROMULAN, a multicyclic controlling computer program, is introduced. Implications of the introduction of multicyclic systems into helicopters are also discussed.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Vertica; 4; 1, 19; 1980
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  • 26
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    HEAO A-2 observations of the X-ray spectra of the Centaurus and A1060 clusters of galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: X-ray spectral observations of two nearby low-luminosity clusters of galaxies are presented. For the Centaurus cluster an emission feature at 7.9 keV is detected at about one-third of the strength of the 6.7 keV line. This higher energy line represents K-beta emission from highly ionized iron. In addition, it is demonstrated that for neither the Centaurus nor the A1060 cluster can an isothermal model with an Fe emission line adequately fit the data. Instead, the simplest models which provide acceptable fits include a second, harder component which may be either a second exponential or a power law. The implications of the two-component nature of the continuum on the Fe abundance and the X-ray surface-brightness distribution are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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  • 27
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    Observation and search for gamma rays 1-20 MeV from the Crab, NGC 4151, Cyg X-1, Cyg X-3, CG 135+1 and 3C 273 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Observations and limiting values for the flux of 1-20 MeV gamma rays from the Crab, the Seyfert galaxy NGC 4151, the black hole candidate Cyg X-1, Cyg X-3 and the two nearest quasars CG 135+1 and 3C 273 are reported. Measurements of the energy and scatter angle of gamma rays at zenith angles between 10 and 30 deg were obtained by a balloon-borne double-scatter gamma-ray telescope. The flux from the Crab from 1.2 to 10 MeV is found to be 0.0039 + or - 0.0020 photons/sq cm per sec, and the energy distribution of the flux from 1.2 to 20 MeV is determined. Two-standard-deviation upper limits to the gamma-ray flux in the intervals 1.2-3, 3-5, 5-10 and 10-20 MeV of 0.0003, 0.0002, 0.00006 and 0.00004 photons/sq cm/sec are found for NGC 4151, Cyg X-1 and Cyg X-3, while those of 0.0005, 0.0003, 0.0001 and 0.00004 photons/sq cm per sec are determined for both quasars. These upper limits are interpreted as restricting confirmed gamma-ray sources to the Crab and NP 0532, and as evidence against Seyfert galaxies as the source of cosmic diffuse radiation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 284; Apr. 17
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  • 28
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    Simultaneous X-ray and optical observations of rapid variability in Scorpius X-1 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Copernicus and SAS-3 observations of Sco X-1 during very active states show strong and rapid X-ray flickering with time scales as short as 20 sec. Simultaneous optical photometry reveals similar and remarkably well correlated flickering of lower amplitude. The level of correlation decreases when the X-ray source becomes fainter, but optical and X-ray fluxes, averaged over 1 min, are usually well correlated for B magnitudes less than 12.9. Cross-correlation analysis of the data during periods of high activity shows no really significant time delay between X-ray and optical features, although the cross-correlation function peaks systematically for positive lag values (optical following X-rays). The amplitude of the X-ray flickering exhibits a strong energy-dependence consistent with the well-known intensity versus spectral-hardness relation derived from previous observations. The highly correlated optical activity is interpreted as due to reprocessing of X-ray photons in the binary system.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society; vol. 191
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  • 29
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    Mass loss from UW Canis Majoris (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The present analysis is an application of the theory described by Lucy (1971) for the calculation of P Cygni resonance line profiles formed by isotropic and coherent scattering in spherically symmetric expanding circumstellar envelopes. Copernicus satellite measurements of resonance features in the FUV spectrum of the O 7 supergiant UW Canis Majoris (= HD 57060) are compared with theoretical P Cygni profiles. Grids of line profiles are computed using four free parameters which contain information about the velocity law, ionization equilibrium, temperature, and envelope density. Thus, with the assumption of a spherically symmetric steady flow, and of solar element abundances, the stellar mass loss rate and the electron temperature of the expanding shell can be derived. The mass flow is treated in a fully transonic way, i.e., the Sobolev approximation is applied.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 83; 3, Ma; Mar. 198
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  • 30
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    Measurements of cabin and ambient ozone on B747 airplanes (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: In response to recent concerns over possibly high ozone levels in the cabins of aircraft flying in the stratosphere, simultaneous measurements of the cabin and ambient ozone levels have been made as part of the NASA Global Atmospheric Sampling Program. Examples of the data taken on commercially operated Boeing 747-100 and 747SP airplanes are given for selected flights, together with summary statistics of over 5600 observations. Cabin ozone levels vary with the ambient level and, for unmodified aircraft, are higher on the 747SP than on the 747-100. Modifications to the ventilation system of the 747SP reduced cabin ozone levels by varying amounts up to a factor of 14.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Aircraft; 17; Apr. 198
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  • 31
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    IUE observations of the hot components in two symbiotic stars (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Recent IUE observations reveal striking differences in the UV spectra of two symbiotic stars, R Aqr and RW Hya. RW Hya is found to be an unexpectedly intense source of UV radiation. The measurements reported demonstrate the presence of a hot component in each star, supporting the view that each is a binary system with a luminous red primary and a hot, subluminous companion. In one case, the hot companion manifests itself by exciting a compact nebulosity; in the other case the continuous spectrum of the hot star is directly detected, while the continuum of nebulosity excited by the hot star is detected at longer wavelengths.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 284; Mar. 13
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  • 32
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    Collapsing cloud models for Bok globules (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The dynamic collapse of rotating gas clouds is calculated for a wide range of initial conditions. Properties of cloud models are compared with observed radio and optical properties of Bok globules, to test the hypothesis that globules undergo collapse and to determine parameters which are not easily observed. Five of the six globules studied are consistent with collapse models. It is inferred that these objects have masses of about 100 solar masses and ages smaller than their free-fall times. Inferred initial densities are much larger than minimum densities for gravitational collapse, suggesting that collapse is initiated by strong external compression or that globules are fragments of larger condensed clouds. Values inferred for the (C-13)O/H2 ratio are smaller than previous estimates and depend strongly on cloud density.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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  • 33
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    Cosmological tests of the Hoyle-Narlikar conformal gravity (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: For the first time the Hoyle-Narlikar theory with creation of matter and a variable gravitational constant G, is subjected to the following cosmological tests: (1) the magnitude versus z relation, (2) the N(m) versus m relation for quasars, (3) the metric angular diameters versus z relation, (4) the isophotal angles versus z relation, (5) the log N-log S radio source count, and finally (6) the 3 K radiation. It is shown that the theory passes all these tests just as well as the standard cosmology, with the additional advantage that the geometry of the universe is uniquely determined, with a curvature parameter equal to zero. It is also interesting to note that the variability of G affects the log N-log S curve in a way similar to the density evolution introduced in standard cosmologies. The agreement with the data is therefore achieved without recourse to an ad hoc density evolution.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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  • 34
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    Radial distribution of forbidden Fe X and forbidden Fe XIV emission in the Cygnus Loop. II (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
    Format: text
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  • 35
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    On C4H versus vibrationally excited CO in IRC + 10216 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The identification of the 114,221-MHz line in the spectrum of the evolved carbon star IRC +10216 with a blend of the rotational transition of C4H and the first rotational transition of vibrationally excited CO is investigated. A spectrum of the source was obtained using an 11-m telescope in the range covering the N = 12 to 11 and 11 to 10 spin-doublet rotational transitions of C4H. Two peaks of equal intensity and width are found in each band, suggesting a spin rotation constant of 1.06 for the 12 to 11 doublet and 1.09 for the 11 to 10 doublet, and excluding the possibility that vibrationally excited CO made any contribution to the 12 to 11 doublet. An additional survey of the regions from 103.8 to 107.5 and 113.3 to 117.0 GHz has revealed no new lines stronger than 0.1 K in the spectrum of IRC +10216.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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  • 36
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    Case for an open universe (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The determination of the geometrical structure of the universe through the magnitude-vs-redshift relation in standard cosmology has not been very successful, mainly because of the intrinsic insensitivity of the m-vs-z relation to a deceleration parameter, which determines the spatial curvature and therefore the geometry. By relaxing the assumption usually made, i.e., the identity of gravitational and atomic clocks, sufficient sensitivity is achieved. Existing observational evidence then leads one to conclude that the universe is open.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Physical Review Letters; 44; Mar. 17
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  • 37
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    Black holes, quasars, and the universe /2nd edition/ (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Topics of astronomy are discussed in terms of black holes, galaxies, quasars, and models of the universe. Black holes are approached through consideration of stellar evolution, white dwarfs, supernovae, neutron stars, pulsars, the event horizon, Cygnus X-1, white holes, and worm holes. Attention is also given to radio waves from high speed electrons, the radiation emitted by quasars, active galaxies, galactic energy sources, and interpretations of the redshift. Finally, the life cycle of the universe is deliberated, along with the cosmic time scale, evidence for the Big Bang, and the future of the universe.
    Schlagwort(e): ASTROPHYSICS
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  • 38
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    Turbulence and the stability of molecular clouds (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Molecular clouds may be stabilized against gravitational collapse by the turbulent velocity field within them. It is suggested that the energy derived from differential galactic rotation can maintain the turbulent flow in the interstellar medium. The characteristic decay time for interstellar turbulence is found to be about 10-billion years. The rate and efficiency of star formation in giant molecular clouds reflect the stochastic nature of turbulence.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 242
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  • 39
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    A wave model for dwarf novae (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The rapid coherent oscillation during a dwarf nova outburst is attributed to an accretion-driven wave going around the white dwarf component of the binary system. The increase and decrease in the period of this oscillation is due to the change in the velocity of the wave as it is first being driven and then damped. Qualitatively, a large number of observations can be explained with such a model. The beginnings of a mathematical representation of this model are developed.
    Schlagwort(e): ASTROPHYSICS
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  • 40
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    Collapse, equilibrium, and fragmentation of rotating, adiabatic clouds (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Numerical calculations of the collapse of adiabatic clouds from uniform density and rotation initial conditions show that when restricted to axisymmetry, the clouds form either near-equilibrium spheroids or rings. Rings form in the collapse of low thermal energy clouds and have a ratio of rotational kinetic energy to the absolute value of gravitational potential energy greater than approximately 0.43. When the axisymmetric constraint is removed and an initial m = 2 density variation is introduced, clouds either collapse to form near-equilibrium ellipsoids or else fragment into binary systems through a bar phase. Ellipsoids form in the collapse of high thermal energy clouds and have a rotational kinetic energy/absolute value of gravitational potential energy ratio less than approximately 0.27. The results are consistent with the critical values of the rotational kinetic energy/absolute value of gravitational potential energy ratio for instabilities in Maclaurin spheroids, and suggest that protostellar clouds may undergo a dynamic fragmentation in the nonisothermal collapse regime.
    Schlagwort(e): ASTROPHYSICS
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  • 41
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    Illustration of airfoil shape effect on forward-swept wing divergence (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: A static aeroelastic analysis is presented of the divergence of untapered wings with conventional and supercritical airfoil sections at sweep angles of zero and -15 deg. One bending and one torsion mode were employed for a uniform rectangular cantilevered beam with the elastic axis at midchord, and calculations were based on a two-dimensional differential equations formulation in the structural coordinate system and in simple strip theory. A minimum divergence speed in the transonic range is obtained which is associated with the rearward shift of the aerodynamic center, and a 17% difference in minimum divergence dynamic pressure is found between a supercritical and a conventional wing. It is noted that although the strip method employed allows the assessment of the sensitivity of airfoil shapes to divergence, three-dimensional transonic aerodynamic methods should be used to predict wing divergence characteristics.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Aircraft; 17; Oct. 198
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  • 42
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    X-ray line emission from the supernova remnant G292.0 + 1.8 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The Solid State Spectrometer on the Einstein Observatory has detected line emission from Mg, Si and S in the thermal X-ray spectrum of the supernova remnant G292.0 + 1.8. An over-abundance of sulfur and a probable under-abundance of iron relative to their solar values is indicated by the data. The X-ray and optical data for this object support an interpretation of emission originating in ejecta from the comparatively recent explosion of a massive (about 20-solar-mass) progenitor star.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society; vol. 193
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  • 43
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    A survey of chromospheric Ca II H and K emission in field stars of the solar neighborhood (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Fluxes in 1 A bands at the centers of the H and K lines are being measured in main-sequence F-G-K-M stars in the northern half of the Woolley et al. (1970) 'Catalog of stars within twenty-five parsecs of the sun', in a survey not yet completed. Results for 486 stars are presented in the form of flux-color diagrams and discussed in light of evidence that chromospheric activity declines with age in main-sequence stars. Support is noted for the reality of the Sirius moving group. The relative numbers of more-active (Hyades-like) and less-active (solar-like) F-G stars are tolerably in agreement with a nearly constant rate of formation, but there exists an apparent deficiency in the number of F-G stars exhibiting intermediate activity. The possibility that the gap is an accidental characteristic of the sample will be investigated by extending the survey to southern declinations and greater distances.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific; vol. 92
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  • 44
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    The X-ray pulsars 4U 1145-61 and 1E 1145.1-6141 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Observations of the neighboring X-ray pulsars 4U 1145-61 and 1E 1145.1-6141 obtained by OSO 8, HEAO 1 and the Einstein Observatory between 1975 and 1979 are reported. A temporal analysis of Einstein Solid State Spectrometer and Monitor Proportional Counter data, OSO 8 A and C detector data and HEAO 1 A-2(3) experiment data confirms the presence of two periodicites at 291 and 297 sec in the region, with the shorter period located within 3 arcmin of 4U 1145-61. Observations indicate the spectrum of 4U 1145-61 to obey a power law with an index of 1.5 out to at least 60 keV, with little variation with pulse phase, and a 500-eV EW iron line at 6.7 keV. The spectrum of the other source is found to be more absorbed. Similarities between the pulsars are noted, and it is suggested that they may be the result of pulsar formation in a homogeneous cloud of progenitors.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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  • 45
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    Observations of Cygnus X-3 with the Einstein /HEAO 2/ X-ray Observatory The period derivative and the asymmetric X-ray light curve (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Cygnus X-3 was observed by the Monitor Proportional Counter on the Einstein (HEAO 2) X-ray Observatory for 2.4 days in 1978 December. The analysis of the data from these observations is used in conjunction with a self-consistent re-examination of previous results from the Uhuru, ANS, COS B, and SAS 3 satellites to investigate earlier reports that the 4.8 hour period of Cygnus X-3 is increasing. It is found that there is indeed a period derivative, P = (1.78 plus or minus 0.40) x 10 to the -9th s/s, which confirms the principal conclusion of previous authors. The possibility that the X-ray source is in an elliptical orbit and that some, or all, of the observed period derivative may be due to apsidal motion is discussed. The elliptic orbit hypothesis explains the observed asymmetry in the average X-ray light curve and leads to the conclusion that the most likely companion to the X-ray source is a helium star, possibly with a light hydrogen envelope
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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  • 46
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    An observational H-R diagram for early-type stars (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: An observational H-R diagram for the O and B stars is discussed and compared with the predicted positions of massive model stars for the case of no mass loss and the case of mass loss. It is shown that the flux effective temperatures of O and B supergiants and of early O stars are less than the effective temperatures which might be inferred from the relative intensities of lines from two stages of ionization of an element.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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  • 47
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    X-ray observations of the Seyfert 1 galaxies AKN 120 and MCG 8-11-11 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: A new X-ray source, H0523-00, with the optically variable Seyfert 1 galaxy AKN 120 is identified. The source has a 2-10 keV X-ray flux of 2 x 10 to the -11th ergs/sq cm s which corresponds to a 2-10 keV X-ray luminosity of 10 to the 44th ergs/s. X-ray observations over a 1.5 year time span combined with contemporaneous optical photometry show a decrease in the optical with no corresponding decrease in the X-ray. In contrast, similar observations of MCG 8-11-11 show a contemporaneous decrease in optical and X-ray fluxes. It is noted that the infrared and X-ray spectral slopes for these two objects are similar, with the optical being steeper by roughly one unit.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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  • 48
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    The detection of a companion star to the Cepheid variable Eta Aquilae (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Ultraviolet spectra have been obtained with IUE of the classical Cepheid Eta Aquilae at several phases in the 7.18 day period. Significant ultraviolet emission is detected at wavelengths less than 1600 A, where little flux is expected from classical Cepheids. Furthermore, the emission at wavelengths less than about 1600 A does not vary with phase. Comparison with model atmosphere flux distributions shows that the nonvariable emission is consistent with the flux expected from a main-sequence companion star with an effective temperature of about 9500 K (A0 V). The observed ultraviolet flux and spectral type are used to compute a distance of 300 pc to the system, in agreement with the distance predicted using the period luminosity relation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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  • 49
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    On the time variability of Circinus X-1 - A comparison with Cygnus X-1 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The time variability and spectral characteristics obtained from Uhuru observations of Cir X-1 (4U 1515-56) are compared with observations of Cyg X-1 (4U 1956+35). It is found that Cir X-1 has a more variable spectrum (with perhaps a state over the 4 days spanned by the data), is less 'noisy', and has correlated fluctuations (as evidenced by the nonzero cross-correlation function between two energy bands) of shorter duration than those present in the shot noise of Cyg X-1.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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  • 50
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    X-rays from RS Canum Venaticorum systems - A HEAO 1 survey and the development of a coronal model (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The paper presents HEAO 1 low-energy X-ray observations of 59 known or suspected RS CVn systems cited in the lists of Hall (1976), Eggen (1978), and the circulars of the Working Group on RS CVn systems of IAU Commission 42. The data are used to argue against the validity of the minimum flux coronal models. A coronal loop model is used to derive expressions for the loop parameters in terms of observable quantities, and find acceptable solutions for RS CVn systems. It is concluded that the difference between solar activity and that observed in RS CVn systems may be merely a matter of scale.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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  • 51
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    Comments on stellar boundary cooling and the reality of supermetallicity (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The paper discusses the 'super-metal-rich' (SMR) stars and reexamines Peterson's analysis of the SMR prototype mu Leo (1978) with regard to a postulated error in continuum error. Model atmospheres are used to compute theoretical equivalent widths and to explore the sensitivity of these widths to metallicity, temperature, surface gravity, and microturbulence. It is shown that Peterson's results are sensitive to continuum placement, and that her data does not indicate that the temperature gradient is steeper in mu Leo than in normal giants. It is concluded that the SMR stars are very metal rich and are also somewhat boundary cooled, possibly due to high metallicity.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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  • 52
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    Gamma rays from Penrose powered black holes in Centaurus A, 3C 273, and NGC 4151 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Gamma-ray observations of Cen A, 3C 273, and NGC 4151 are examined under the assumption that Penrose collision processes in the ergospheres of massive black holes power their nuclei. The observed sharp break in the MeV region of the NGC spectrum is attributed to Penrose Compton scattering, and the absence of an MeV break in the spectra of Cen A and 3C 273 implies Penrose pair production. Central black hole masses of tens of millions of solar masses for NGC 4151 and Cen A, and tens of billions of solar masses for 3C 273, are obtained. Attention is also given to accretion rate, the efficiency of accretion, QSOs and Seyferts.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 236
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    The plane of symmetry of interplanetary dust in the inner solar system (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Observations of the zodiacal light from the space probes Helios 1 and 2 between 1.0 and 0.3 AU show - superimposed on the general radial dependence - a systematic variation of brightness and brightness distribution with position in the orbit which is caused by the inclination of the symmetry plane of interplanetary dust with respect to the ecliptic. By suitable choice of the observing geometry, the inclination and the ascending node of the symmetry plane can be determined directly from the data without recourse to model calculations. The resulting values of i equals 3.0 plus or minus 0.3 deg, Omega equals 87 plus or minus 4 deg are not compatible with a concentration of interplanetary dust to the invariable plane of the solar system. The data support the simple view that the distribution of interplanetary dust in the inner solar system is characterized throughout by one plane of symmetry and suggest that this plane extends to at least 1 AU.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 82; 3, Fe; Feb. 198
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  • 54
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    A laboratory study of magnesium-tetrabenz-porphyrin - Lack of agreement with diffuse interstellar bands (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The visible and infrared spectra and thermal behavior of the bis-pyridal-magnesium-tetrabenz-porphyrin molecule proposed as the carrier of the diffuse interstellar bands were measured. Of the six band coincidences reported by Johnson (1977), only one, 4430 A, occurs in these experiments. This coincidence requires a special environment, not likely to occur in interstellar space but the infrared spectrum does not support Johnson's vibrational scheme. These spectroscopic and thermal measurements contradict the hypothesis that this molecule causes the diffuse bands.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysics and Space Science; 68; 1, Ma; Mar. 198
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    Production of carbon, sulfur, and CS in Comet West (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Results from ultraviolet spectrographic observations of Comet West (1975n) in the 1620-3960 A wavelength range are presented. Objective grating imagery of the comet reveals for the first time emission from sulfur atoms and CS molecules as well as previously observed lines or bands in carbon atoms and CO(+), CO2(+) and OH molecules. Some evidence exists for emission in the C2 Mulliken bands and in the CO Cameron bands. On the basis of the observations, production rates of C (ground state), C(1D), S, and CS are inferred to be 3.8 x 10 to the 29th per sec, 4.4 x 10 to the 29th per sec, 1.7 x 10 to the 28th per sec, and greater than approximately 3.1 x 10 to the 27th per sec, respectively.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 242
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    The diffuse gamma-ray background in the Hoyle-Narlikar cosmology (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper analyzes the contributions of QSOs, BL-Lac objects and Seyfert galaxies to the diffuse gamma-ray background within the framework of the Hoyle-Narlikar theory. It is shown that the inconsistency reported in standard theory, namely that the evolutionary function needed to explain the gamma-ray data is very different from the one derived from the optical part of the spectrum, is no longer present. It is also shown that the contribution of a variable gravitational 'constant' to the expression for the diffuse background is the same as that of a density evolution function.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 92; 1-2,; Dec. 198
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    Neutrino, gamma-ray, electron, and positron production in an ultrarelativistic plasma (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Neutrino, gamma-ray, electron and positron production resulting from inelastic proton-proton collisions in a highly relativistic plasma such as may exist in extragalactic radio or gamma-ray burst sources is examined. The source functions of primary (pions, kaons, and neutrons) and secondary (photons, electrons, positrons and neutrinos) products of relativistic nuclear collisions are computed for the cases of power law and Maxwellian relativistic proton distributions. It is shown that in plasma which is optically thin to interactions between the plasma and secondary gamma-rays, electrons and positrons, only a small fraction of the initial energy is emitted in the observable form of neutrinos and gamma rays. In an optically thick plasma on the other hand, most of the energy of the relativistic protons is found to be equally divided between gamma rays and neutrinos, although only the neutrinos may escape freely to be observed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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    Dust-to-gas ratio in the outer regions of spiral galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Some spiral galaxies are surrounded by extended clouds of neutral hydrogen; if dust is associated with this gas, the dust should appear as a faint extended reflection nebula illuminated by the light from the entire galaxy. It is suggested that observations of the surface brightness of the outer regions of M83 and M101 could be worthwhile, since these two galaxies are bright and have extended surrounding gas clouds. Such studies would be of interest with regard to the possible presence of faint extended halos of stars around galaxies, the extent of the metallicity gradients in galaxies, and the value of the dust-to-gas ratio in quasar absorption-line systems.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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    X-ray observations of Algol (1980)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The Solid State Spectrometer on Einstein has been used to study Algol. Two observations six months apart were made, both including a primary optical eclipse. No corresponding X-ray eclipses were seen. During the second observation the source was flaring and was on the average a factor of three brighter. The spectrum on both occasions was consistent with a two-component thermal equilibrium model with temperatures of approximately 7.5 and 40 million degrees. Attempts to insert a third component indicate the temperature distribution to be bimodal. Models for the X-ray emission are discussed and it is suggested that it most likely originates from an active corona surrounding the K star.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
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    Far-infrared spectra of W51-IRS 2 and W49 NW (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Measurements of the far-infrared spectra of the powerful H II regions W51-IRS 2 and W49 NW from 65 to 345 per cm with about 9 per cm resolution were obtained by using an airborne Michelson interferometer. The most remarkable feature of the far-infrared spectra of the two regions is the smoothness of the continuum; no evidence is found in the spectra for features of H2O ice at 45 and 62 microns. The spectrum of W51 is well fitted by a 70 K blackbody with a diameter of 14 arc sec, but the spectrum of W49 NW is narrower than a blackbody. The implications of the apparently high peak optical depths of these sources are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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    Stellar winds, supernovae, and the origin of the H I supershells (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: It is shown that the H I shells and supershells, recently reported by Heiles, are a natural by-product of the interaction of the stellar winds and supernovae, originating from stars in typical OB associations, with the surrounding interstellar medium. The validity of this model is supported by its ability to reproduce observed characteristics of the shells such as the shell sizes and shapes as a function of their distances from the galactic center. This process may also be responsible for injecting synthesized elements into the galactic halo.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 238
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    The evolution of the dust shell of Nova Serpentis 1978 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Photometric measurements of Nova Serpentis 1978 from V to 19.5 microns covering the first 240 days of the nova's development are reported. A free-free expansion phase was followed by the condensation of a dust shell that became optically thick at both visible and infrared wavelengths. Carbon grains grew to radii of approximately 0.3 microns during the condensation period. The grains appeared to sputter or evaporate for a period of approximately 100 days following infrared maximum. It is found that the condensed carbon comprised 2% of the ejected mass, which implies that carbon abundance was enhanced in the nova shell. The angular expansion rate of the shell yields a distance of approximately 5 kpc and a luminosity of approximately 3000 solar luminosities for Nova Serpentis 1978.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 237
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    Cosmological considerations on the diffuse gamma-ray isotropic background (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Bignami et al (1979) have recently studied the problem of the origin of the diffuse gamma-ray isotropic radiation. They have concluded that within standard cosmology with Lambda = 0 and p = 0, BL Lacertae objects and Seyfert galaxies can account for most of the diffuse radiation if they have not evolved in time. For QSOs, an evolutionary factor is allowed by the data. From the study of radio data, however, it is known that strong evolutionary effects are expected. The discrepancy cannot be explained by changing the geometry of the universe. Contrary to the case of standard cosmology, it is found that in order to fit the diffuse gamma-ray background, the evolutionary function required is almost identical to the one previously determined from the study of the log N-log S relation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Helicopter theory (1980)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A comprehensive presentation is made of the engineering analysis methods used in the design, development and evaluation of helicopters. After an introduction covering the fundamentals of helicopter rotors, configuration and operation, rotary wing history, and the analytical notation used in the text, the following topics are discussed: (1) vertical flight, including momentum, blade element and vortex theories, induced power, vertical drag and ground effect; (2) forward flight, including in addition to momentum and vortex theory for this mode such phenomena as rotor flapping and its higher harmonics, tip loss and root cutout, compressibility and pitch-flap coupling; (3) hover and forward flight performance assessment; (4) helicopter rotor design; (5) rotary wing aerodynamics; (6) rotary wing structural dynamics, including flutter, flap-lag dynamics ground resonance and vibration and loads; (7) helicopter aeroelasticity; (8) stability and control (flying qualities); (9) stall; and (10) noise.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
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    Semi-empirical estimates of gravitational wave generation by stellar collapse (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The problems of the generation and detection of gravitational waves and the difficulty of detecting the burst of gravitational radiation produced by a stellar collapse in our Galaxy, or in neighbouring clusters of galaxies where such collapses are expected to occur frequently, have been reviewed elsewhere. As stellar collapses, explosions, or supernovae are poorly understood, the values of the strength of these sources depend on uncertain assumptions. However, it is possible to make some independent estimates on semi-empirical grounds, using observed facts concerning the remnants of stellar evolution. These estimates, reported here, have serious weaknesses. They must involve oversimplified models and very crude standard calculations of the collapse and radiation processes. Also, because they are based on observed properties of stellar remnants, they say nothing about collapses which do not produce observable remnants. Although this selection may introduce a strong bias, these estimates deserve consideration because they are tied to real data.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 283; Feb. 7
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  • 66
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    Galaxies and far-infrared emission (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The far-infrared luminosities of the central few hundred parsecs of many galaxies may exceed by more than an order of magnitude the amount expected from late-type stars. However, for the M82, NGC 253, NGC 1068 and several other galaxies studied in the present paper, the inferred mass-to-luminosity ratios are within the limits expected for stellar distributions containing early-type stars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Relativistic jets and the continuum emission in QSOs (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The radio through optical, and possibly X-ray, emission of QSOs and active galactic nuclei is analytically interpreted in terms of a relativistic jet containing high-energy particles and a magnetic field. Parallel to the jet axis, a strong, compact radio source and strongly polarized radiation are detected, while larger viewing angles relative to the jet axis result in spectral dominance by the central region containing the 'energy machine' which drives the energy flux in the jet. It is shown that the relativistic jet model can explain the association of OVVs with strong, variable radio sources, strong optical polarization, and continuity of the radio to optical spectra.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    HEAO 1 spectra of X-ray emitting Seyfert 1 galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The paper presents the 2-50-keV X-ray spectra and time variability information on seven Seyfert 1 galaxies NGC 3783, NGC 4151, NGC 5548, NGC 6814, MK 509, MCG 8-11-11, and ESO 141-G55, obtained with the A2(2) experiment on HEAO 1. It is concluded that the spectra of Seyfert 1 galaxies can be well represented by flat power laws of high-temperature thermal breamsstrahlung models with relatively low column densities.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    X-ray line emission from the Tycho supernova remnant (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The A-2 experiment onboard HEAO 1 has observed the X-ray spectrum of the Tycho supernova remnant in the energy range 0.5-20 keV. The spectrum reveals four significant line features: the K(alpha) lines of silicon, sulfur, and iron; and the L lines of iron. Comparisons between the silicon and sulfur equivalent widths and K(alpha) iron line energies of Tycho and Cas A suggest that the X-ray emitting plasma in Tycho is further from collisional ionization equilibrium than that in Cas A.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Asymptotic freedom in the early big bang and the isotropy of the cosmic microwave background (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: It is suggested that a superunified field theory incorporating gravity and possessing asymptotic freedom could provide a solution to the problem of the isotropy of the universal 3 K background radiation. Thermal equilibrium could be established in this context through interactions occurring in a temporally indefinite pre-Planckian era.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Elemental abundances in a Type I supernova remnant (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The solid-state spectrometer (SSS) on the HEAO 2 (Einstein) X-ray observatory observed the X-ray spectrum of Tycho's SNR. The observations show a relative excess of line emission from Si, S, and Ar by not less than 6 compared to that expected from a plasma of solar composition in collisional equilibrium and by a factor of not less than 3 compared to Cas A. Similar excesses are not found for line emission from Mg and Fe. The data suggest that the SN observed by Tycho in 1572 produced significant amounts of Si group elements but did not eject large amounts of Fe as predicted by some models of Type I SN events.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Comparison of predicted and observed spectral energy distribution of K and M stars. I - Alpha Bootis (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The K2 IIIp star Alpha Bootis has been observed from the ground at 0.536 to 1.070 microns, and from an airplane at 1.21 to 3.90 microns. In the present paper, an absolute flux curve, constructed from these observations with an overall precision greater than + or - 2% in F-lambda, is compared with previous photometry and spectrometry.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Origin of large interstellar grains toward Rho Ophiuchi (1980)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The paper considers why the interstellar grains toward Rho Oph are unusually large. Because the visual opacity per gram is lower than average toward Rho Oph, it is concluded that the simplest interpretation of the observations is that grain coagulation has occurred. This result may be important for understanding the evolution of interstellar clouds and may provide insight into the initial stages of the formation of large solid bodies such as planets.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    150 GHz observations of three radio galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Radio galaxies were observed for the first time at 150 GHz. The central sources in Cyg A and 3C 111 were detected, as were the two radio lobes of Cyg A. No emission was found from the central source in 3C 236. The millimeter-wavelength emission from the central sources in Cyg A and 3C 111 is probably due in each case to a compact component that is optically thin to synchrotron radiation above about 35 GHz. These components are similar, although the compact component in 3C 111 is more luminous at both radio and X-ray wavelengths than the one in Cyg A. The 3C 111 central source was much weaker than anticipated on the basis of prior observations at 90 GHz, perhaps due to variability. Even at 150 GHz, there is no evidence of a high-frequency cutoff in the spectrum of the central source in Cyg A, and variability of this source also is expected. The flux densities of the Cyg A lobes are consistent with the power laws derived at lower frequencies, indicating that no steepening occurs in their spectra out to at least 150 GHz. There is no evidence for a compact, optically thick component in 3C 236.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 235
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    Small Transport Aircraft Technology (1980)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The article surveys the results of the NASA-instituted Small Transport Aircraft Technology (STAT) research effort aimed at generating advanced technologies for application to new small, short haul transports having significantly better performance, efficiency, and environmental compatibility. Discussion covers fuselage designs and bonded aluminum-honeycomb wing construction which reduces the number of parts and fasteners, and gives a smoother outer contour. Topics discussed include: advanced aluminum alloys, composite primary structures, propellers, engine components, icing protection, avionics, flight controls, aerodynamics, and gust load alleviation.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Astronautics and Aeronautics; 18; Feb. 198
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    Constrained optimum trajectories with specified range (1980)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The characteristics of optimum fixed-range trajectories whose structure is constrained to climb, steady cruise, and descent segments are derived by application of optimal control theory. The performance function consists of the sum of fuel and time costs, referred to as direct operating costs (DOC). The state variable is range-to-go and the independent variable is energy. In this formulation a cruise segment always occurs at the optimum cruise energy for sufficiently large range. At short ranges (500 n. mi. and less) a cruise segment may also occur below the optimum cruise energy. The existence of such a cruise segment depends primarily on the fuel flow vs thrust characteristics and on thrust constraints. If thrust is a free control variable along with airspeed, it is shown that such cruise segments will not generally occur. If thrust is constrained to some maximum value in climb and to some minimum in descent, such cruise segments generally will occur. The performance difference between free thrust and constrained thrust trajectories has been determined in computer calculations for an example transport aircraft.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Guidance and Control; 3; Jan
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    Magnetohydrodynamic perturbations of Robertson-Walker universes and of anisotropic Bianchi type-I universes (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Magnetohydrodynamic (MHD) perturbations in flat Robertson-Walker universes were analyzed, emphasizing their effects on galaxy formation. The Newtonian approximation is used. There is no increase in the growth rates beyond those of the usual perturbed Robertson-Walker models; the MHD modes extract as much energy as they contribute. Some global properties of fully MHD Bianchi I relativistic models are analyzed including vorticity, fluid accelerations, and dissipative effects. The time dependence of perturbations of a fully MHD diagonal Bianchi I cosmology is studied, with an enhanced growth rate of the density contrast of t found which is still not exponential Jeans-type growth. This indicates that a more detailed analysis is needed if a solution to the galaxy formation problem in MHD cosmologies is to be found.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nuovo Cimento B; vol. 60B
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    Shipboard trials of the Quiet Short-Haul Research Aircraft /QSRA/ (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The feasibility of the application of advanced state-of-the-art high lift STOL aircraft in the aircraft carrier environment was evaluated using the NASA Quiet Short-Haul Research Aircraft (QSRA). The QSRA made repeated unarrested landings and free deck takeoffs from the USS Kitty Hawk while being flown by three pilots of significant different backgrounds. The exercise demonstrated that the USB propulsive lift technology presents no unusual problems in the aircraft carrier environment. Optimum parameters for landing the QSRA were determined from the shore-based program; these proved satisfactory during operations aboard ship. Correlation of shipboard experience with shore-based data indicates that both free deck takeoffs and unarrested landings could be conducted with zero to 35 knots of wind across the deck of an aircraft carrier the size of the USS Kitty Hawk.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
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    The XV-15 tilt rotor research aircraft (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The XV-15 tilt rotor has shown good handling qualities in all modes of flight; in the helicopter mode it allows precision hover and agility with low pilot workload. Vibration and noise levels are low; the conversion procedure is easy, with satisfactory acceleration or deceleration. The XV-15 handling demonstrated its potential for many civil and military applications.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
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    Dynamics of the universe and spontaneous symmetry breaking (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is shown that the presence of a phase transition early in the history of the universe, associated with spontaneous symmetry breaking (believed to take place at very high temperatures at which the various fundamental interactions unify), significantly modifies its dynamics and evolution. This is due to the energy 'pumping' during the phase transition from the vacuum to the substance, rather than the gravitating effects of the vacuum. The expansion law of the universe then differs substantially from the relation considered so far for the very early time expansion. In particular it is shown that under certain conditions this expansion law is exponential. It is further argued that under reasonable assumptions for the mass of the associated Higgs boson this expansion stage could last long enough to potentially account for the observed isotropy of the universe.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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    Interplanetary gas. XXV - A solar wind and interplanetary magnetic field interpretation of cometary light outbursts (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Possible relationships of cometary brightness outbursts with the solar wind and interplanetary magnetic field are examined. Two types of outburst are distinguished: those which involve a significant brightening of both the head and the tail in a comet with a conspicuous plasma tail (Class I), and those involving the brightening of the central condensation of a previously faint comet with no detectable plasma tail (Class II). Class I bursts, as exemplified by Comet Morehouse 1908c, are attributed to the generation in the head of enhanced amounts of ions and their injection into the tail shortly before it disconnects, with ionization provided by sector boundary crossings. Class II events, as exhibited by Comet P/Tuttle-Giacobini-Kresak 1973b, are interpreted as the result of the bombardment of the nucleus by disturbed solar wind near corotated high-speed streams and sector boundaries, leading to highly exothermic chemical reactions.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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    Electron densities for six planetary nebulae and HM Sagittae derived from the semiforbidden C III lambda 1907/1909 ratio (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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  • 83
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    IUE observations of a luminous M supergiant that exhibits emission continuum in the far ultraviolet (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: IUE observations of the late-type M supergiant star TV Gem which reveal an intense continuum in the far ultraviolet are discussed. TV Gem was observed in low dispersion in November 1979 and in high and low dispersion in January 1980 by the short and long wavelength cameras of the IUE spectrometer. An essentially featureless UV continuum was obtained, with the exception of a number of broad absorption features in the short wavelength region. A comparison with ground-based observations indicates that at wavelengths greater than 3200 A the continuum emission is essentially due to the M1 supergiant, while at shorter wavelengths the continuum is dominated by a hot companion. The UV continuum can be explained by a B9 or A1 III-IV early companion approximately 2 to 3 magnitudes fainter than the M1 supergiant, or by an accretion disk formed by mass transfer from the extended envelope of the M1 primary onto the surface of a highly condensed secondary. Soft X-ray observations from HEAO 2 are suggested as a means to investigate these interpretations.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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  • 84
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    B2 1141 + 37 - A giant radio galaxy with remarkable radio and optical properties (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of the giant radio galaxy B2 1141+37, which has a widely separated two-component radio structure and is optically identified with a tight chain of galaxies, are reported. The source was observed at 4900 MHz with the VLA at an effective integration time of 17 min. The map obtained shows two radio lobes with maxima coinciding with those in a previous 1415 MHz map and intensities about 1.5 times smaller than those obtained by extrapolating the spectrum defined by the flux density at 408 and 1415 MHz. Measurements of the redshifts of the two brightest galaxies identified with the radio source with an image intensified dissector scanner result in values of 0.1145 and 0.1155, which imply, with a Hubble constant of 50 km/sec per Mpc, a distance of 687 Mpc to the radio source and a separation of 1.0 Mpc between the lobes making it one of the largest radio sources known.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 288; Dec. 4
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  • 85
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    Application of an advanced trajectory optimization method to ramjet propelled missiles (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The mission performance characteristics of ramjet-propelled missiles are highly dependent upon the trajectory flown. Integration of the trajectory profile with the ramjet propulsion system performance characteristics to achieve optimal missile performance is very complex. Past trajectory optimization methods have been extremely problem dependent and require a high degree of familiarity to achieve success. A general computer code (CTOP) has been applied to ramjet-powered missiles to compute open-loop optimal trajectories. CTOP employs Chebyshev polynomial representations of the states and controls. This allows a transformation of the continuous optimal control problem to one of parameter optimization. With this method, the trajectory boundary conditions are always satisfied. State dynamics and path constraints are enforced via penalty functions. The presented results include solutions to minimum fuel-to-climb, minimum time-to-climb, and minimum time-to-target intercept problems.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Optimal Control Applications and Methods; 1; Oct
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  • 86
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    A very rapid turning of the plasma-tail axis of comet Bradfield 19791 on 1980 February 6 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Schmidt camera photographs of comet Bradfield 19791 obtained at the Joint Observatory for Cometary Research (JOCR) indicate that a rapid change took place in the comet's plasma tail on 1980 February 6. On that date, a sequence of photographs spanning 27.5 minutes shows a 10 deg shift occurring in the plasma-tail axis between the first and last exposures. The speed of this tail-turning event greatly exceeds that of any other known event and even exceeds turning rates for individual tail streamers. An interpretation based on the windsock theory of plasma tails is that the comet entered a region of rapidly changing solar-wind flow direction. While the search for an associated solar-wind event from near-earth spacecraft observations is a future activity, the present analysis shows that a 50 km/s change in the polar component of the solar-wind velocity, from about 30 km/s northward to about 20 km/s southward, would have produced the 10 deg shift in the tail axis.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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  • 87
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    X-ray spectral constraints on the broad-line cloud geometry of NGC 4151 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: X-ray spectral data from NGC 4151 taken with the Einstein Solid-State Spectrometer (SSS) and the HEAO 1 A-2 experiment cannot be simply reconciled with absorption from a uniform column of cold gas. The SSS data can, however, be explained in terms of a clumped absorber with approximately 10% uncovered fraction and factor-of-two overabundances in Z equal to or greater than 14 elements relative to solar oxygen. It is shown that these and previously reported spectral and variability data can be quantitatively reconciled with absorption arising in the cold clouds responsible for the broad optical line emission if the cloud dimensions are small compared to the central source size. It is suggested that the lack of significant X-ray absorption observed from much higher luminosity Seyferts and quasars is a natural consequence of the proposed picture for NGC 4151.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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  • 88
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    A search for interstellar pyrrole - Evidence that rings are less abundant than chains (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Searches for three transitions of pyrrole (C4H5N) give maximum column density = 3-10 x 10 to the 13th per sq cm in Sgr B2. This limit is more than 10 times lower than previous ring molecule limits, and is slightly lower than column densities of known interstellar molecules with from four to six heavy atoms.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 241
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  • 89
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    Circular polarization from scattering by circumstellar grains (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is suggested that observations of circular polarization can be a valuable tool for the study of circumstellar nebulae. A simple model is presented to predict the percentage of circular polarization produced by scattering from the dust contained within such nebulae; it was found that a significant component of circular polarization can be produced in nebulae which have a net linear polarization. Possible observations of the red supergiants mu Cep and alpha Ori are given as examples.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Journal; 85; Nov. 198
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  • 90
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    A suggestion concerning the generation of the physical state of stellar mantles (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The physical state of the winds of B supergiants varies from one of a high level of ionization and rapid outflow to one of relatively low ionization and a moderate rate of outflow as one goes from type B0 to type A0. It is proposed here that this is the result of magnetodynamic energy being released in the mantles of these stars, much as occurs in the sun. Data are presented to show that this idea is plausible. It is noted that the release of magnetodynamic energy as the result of interaction between magnetic fields and differential motion in an inhomogeneous structure is probably the cause of the heating in all outer stellar atmospheres (mantles). In the late-type stars, the material in the mantle must first be ionized by the deposition of energy from acoustic waves; in the early-type stars, the material is already ionized at least once in the photosphere, as a result of the normal transfer of radiative energy, so no priming process is necessary for these stars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 240
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  • 91
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    Influence of a stellar wind on the evolution of a star of 30 solar masses (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A coarse grid of theoretical evolutionary tracks was calculated for a 30 solar mass star to determine the role of mass loss in the evolution of the star during core He burning. The Cox-Stewart opacities were applied, and the rate of mass loss, criterion for convection, and initial chemical composition were taken into consideration. Using the Schwarzschild criterion, the star undergoes little mass loss during core He burning and remains a blue supergiant separated from main sequence stars on the H-R diagram. The stellar remnant consists of the original He core and may appear bluer than equally luminous main sequence stars; a variety of possible evolutionary tracks can be obtained for an initial solar mass of 30 with proper choices of free parameters.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 240
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  • 92
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    Theoretical profiles for the 1-0 S/1/ H2 line in carbon stars (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The spectra of carbon stars have been synthesized from the models of Querci, Querci, and Tsuji and Querci and Querci in the region of the 1-0 S(1) vibration-rotation quadrupole line of H2. The line is shown to be sufficiently strong to be seen against the numerous lines of the CN red system for models with effective temperatures less than about 2700 K. The usefulness of the line as a diagnostic of the atmosphere is discussed, and a comparison with the measured spectra of UU Aur and S Cep is made. It is concluded that the outer atmospheric layers of carbon stars are significantly warmer than the models predict. An additional opacity source in the outer layers is required.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 240
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  • 93
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    The X-ray spectrum of QSO 0241 + 622 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The X-ray spectrum of QSO 0241 + 622 in the range 2-50 keV measured with the Goddard Space Flight Center proportional counters on OSO 8 is presented. The quasar is similar to 3C 273 in the proportion of energy emitted in various bands, excluding the radio, if reported radiation above 50 keV from its direction is indeed associated with QSO 0241 + 622. Comparisons are made between the two quasars in a discussion of possible energy generation scenarios. Implications concerning quasar contributions to the diffuse background are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 240
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  • 94
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    The Penrose Photoproduction Scenario for NGC 4151 /PCS-SSC/ - A black hole gamma-ray emission mechanism for active galactic nuclei and Seyfert galaxies (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: On the basis of general arguments, it has been suggested (Bignami et al., 1979) that a steepening of the spectrum between X-ray and gamma-ray energies may be a general, gamma-ray characteristic of Seyfert galaxies, if the diffuse gamma-ray spectrum is considered to be a superposition of unresolved contributions, from one or more classes of extragalactic objects. It is shown that the above suggestion can be given a consistent theoretical interpretation in the context of the Penrose Photoproduction Scenario (PCS-SSC). Specifically in the case of NGC 4151, the dominant process will be shown to be Penrose Compton Scattering PCS in the ergosphere of a massive, central, rapidly spinning Kerr black hole, assumed in its nucleus. It is assumed that PCS gamma-ray induced electron-position, Synchrotron-Self-Compton processes 'evolve' as the dominant source of nonthermal X-rays.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 89; 3, Se; Sept
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  • 95
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    Supersonic cruise vehicle research/business jet (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A comparison study of a GE-21 variable propulsion system with a Multimode Integrated Propulsion System (MMIPS) was conducted while installed in small M = 2.7 supersonic cruise vehicles with military and business jet possibilities. The 1984 state of the art vehicles were sized to the same transatlantic range, takeoff distance, and sideline noise. The results indicate the MMIPS would result in a heavier vehicle with better subsonic cruise performance. The MMIPS arrangement with one fan engine and two satellite turbojet engines would not be appropriate for a small supersonic business jet because of design integration penalties and lack of redundancy.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Supersonic Cruise Res., 1979, Pt. 2; p 935-949
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  • 96
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    A family of supersonic airplanes: Technical and economic feasibility (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: To improve the prospects for success in the market place, the family approach is essential to the design of future supersonic airplanes. The evolution from a basic supersonic airplane to a family could follow historic patterns, with one exception: substantial changes in passenger carrying capacity will be difficult by the conventional fuselage "doughnut" approach so successfully used on the cylindrical fuselage of subsonic airplanes. The primary reasons for this difference include the requirement for highly integrated "area ruled" configurations, to give the desired high supersonic aerodynamic efficiency, and other physical limitations such as takeoff and landing rotation. A concept for a supersonic airplane family that could effectively solve the variable range and passenger capacity problem provides for modification of the fuselage cross section that makes it possible to build a family of three airplanes with four, five, and six abreast passenger seating. This is done by replacing or modifying portions of the fuselage. All airplanes share the same wing, engines, and major subsystems. Only small sections of the fuselage would be different, and aerodynamic efficiency need not be compromised.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Supersonic Cruise Res., 1979, Pt. 2; p 833-854
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  • 97
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    Overview of Boeing supersonic transport efforts, 1971 - 1979 (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Following cancellation of the United States Supersonic Transport program, the status of the technology was assessed carefully and emphasis was put on finding solutions for what were considered the major technical difficulties. In particular, work on the breakthroughs needed to advance the technology was emphasized. Currently, solutions to all major technical problems are identified. Depending on the subject, either the problem is no longer a concern or the steps needed to bring about a solution are mapped out clearly. Throughout the NASA SCR program, important strides were made in the identification of design advances which would greatly improve supersonic airplane fuel efficiency, noise, and other performance and cost affecting parameters. Furthermore, these efforts created an atmosphere in which it was possible for new ideas to flourish and positive inventions to take place such as the variable cycle engine and the blended fuselage. These technical gains show that, given availability of such technology, advanced supersonic transports could be developed that would be economically successful and environmentally acceptable.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Supersonic Cruise Res., 1979, Pt. 2; p 821-832
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  • 98
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    Structural concept trends for commercial supersonic cruise aircraft design (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Structural concept trends for future commercial supersonic transport aircraft are considered. Highlights, including the more important design conditions and requirements, of two studies are discussed. Knowledge of these design parameters, as determined through studies involving the application of flexible mathematical models, enabled inclusion of aeroelastic considerations in the structural-material concepts evaluation. The design trends and weight data of the previous contractual study of Mach 2.7 cruise aircraft were used as the basis for incorporating advanced materials and manufacturing approaches to the airframe for reduced weight and cost. Structural studies of design concepts employing advanced aluminum alloys, advanced composites, and advanced titanium alloy and manufacturing techniques are compared for a Mach 2.0 arrow-wing configuration concept. Appraisals of the impact of these new materials and manufacturing concepts to the airframe design are shown and compared. The research and development to validate the potential sources of weight and cost reduction identified as necessary to attain a viable advanced commercial supersonic transport are discussed.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Supersonic Cruise Res., 1979 pt. 2; p 563-587
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  • 99
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    Hydromagnetics and period changes in RR Lyrae stars (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Balazs-Detre and Detre have drawn an interesting parallel between the observed time scales of variability in the sun and in RR Lyrae stars. Additional information is presented here to support their conjecture that an analog of the solar magnetic cycle is operating in RR Lyrae stars. Rough considerations of the expected changes of photospheric radius and of magnetic energy content during a magnetic cycle suggest that the pulsation periods of these stars should also change in time. Within the large observational and theoretical uncertainties, the predicted period changes are compatible with those observed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific; vol. 92
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  • 100
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    Far-infrared survey of the galactic plane (1980)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: The galactic plane has been mapped from L = 352 deg to 45 deg in the band 100-300 microns with beam size of 30 arcmin. Latitudinal and longitudinal distribution of diffuse far-infrared (FIR) emission are given in addition to identifications of the prominent discrete sources with H II and CO emission. FIR luminosities are calculated for the nucleus and the surrounding disk.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 239
    Format: text
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