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  • Inorganic Chemistry  (12,071)
  • ASTROPHYSICS
  • 1975-1979  (5,918)
  • 1965-1969  (4,197)
  • 1925-1929  (4,111)
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Keywords
Publisher
Years
Year
  • 101
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    Ultraviolet spectrophotometry of degenerate stars (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Observations of one helium- and three hydrogen-atmosphere degenerates made with the International Ultraviolet Explorer are discussed. Fluxes in the UV give temperatures in good accordance with those determined from the ground and from the ANS satellite data. Profiles of the strong L-alpha absorption in two DA's fit predictions for the expected temperatures. Gravity determination is vitiated by their steep temperature dependence. If one accepts that theoretical predictions should be correct, corrections to the absolute IUE calibration derived are an upward shift of 3-5%, with irregular residuals attaining + or - 7%.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 102
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    The velocity distribution of interstellar titanium toward Zeta Persei (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Observations of the interstellar 3384-A line of Ti II toward Zeta Persei are reported at a resolution of 1.4 km/s. This resolution exceeds by a factor of almost 3 that used in any previous observations of ions that are dominant stages of ionization in H I regions. Toward Zeta Per, two resolved line components of Ti II having widths generally comparable to those of the corresponding line components of trace ions K I, Ca II, and Na I are seen. For any other ions along this line of sight which have velocity distributions similar to that observed for Ti II, the critical equivalent width above which line saturation must be significant therefore does not exceed 14 mA for ultraviolet lines lying near 1200 A.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 103
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    Centaurus X-3 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectroscopic observations of Krzeminski's star at dispersions 25-60 A/mm are described. The primary is an evolved star of type O6-O8(f) with peculiarities, some of which are attributable to X-ray heating. Broad emission lines at 4640A (N III), 4686 A(He II) and H-alpha show self-absorption and do not originate entirely from the region near the X-ray star. The primary is not highly luminous (bolometric magnitude about -9) and does not show signs of an abnormally strong stellar wind. The X-ray source was 'on' at the time of optical observations. Orbital parameters are presented for the primary, which yield masses of 17 + or - 2 and 1.0 + or - 3 solar masses for the stars. The optical star is undermassive for its luminosity, as are other OB-star X-ray primaries. The rotation is probably synchronized with the orbital motion. The distance to Cen X-3 is estimated to be 10 + or - 1 kpc. Basic data for 12 early-type X-ray primaries are discussed briefly
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 104
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    Influence of a magnetic field on the pulsational stability of stars (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Under certain simplifying assumptions the influence of a magnetic field on the pulsational stability of stars has been investigated, with a particular application to the problem of the stability of upper-main-sequence stars. It has been found that, if the magnetic field averaged over a spherical shell is either constant at all layers or distributed such that nu, the ratio of magnetic to thermodynamic pressure, is constant at all layers, the critical mass for stability against nuclear-energized pulsations is virtually unaffected by the presence of the field. On the other hand, if the field is strong in the envelope but weak in the core of the star, the critical mass is considerably increased; when nu exceeds about 0.1 in the envelope, stability is attained at all masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 105
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    An internal velocity study of the Rosette Nebula (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Emission-line profiles of H-alpha were studied at about 700 points in the Rosette Nebula by using a multislit echelle spectrograph. Numerical analysis of the profiles indicates that variations in the line-of-sight velocity occur within the nebula, reaching about + or - 20 km/s in the inner regions. Evidence is presented that these highest velocities are more probably inward, favoring a model where the central cavity is due to a depletion resulting from rapid star formation
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 106
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    The ultraviolet flux distribution of Alpha-2 Canum Venaticorum (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Intermediate- and narrow-band UV spectrophotometry from Copernicus, OAO 2, the S2-68 experiment on TD 1, and a sounding-rocket experiment are combined with ground-based observations to define the absolute flux distribution of the bright magnetic Ap star Alpha-2 CVn over the wavelength range from 1030 to 7580 A. Two flux distributions are presented which coincide more or less with the rare-earth maximum and minimum in the star's cycle. The results are compared with those for two normal stars, the UV variability of Alpha-2 CVn is characterized as a function of wavelength, and non-LTE effects on the UV continua of C I and Si I are analyzed. Some physical properties of Alpha-2 CVn are estimated, and the evolutionary age of the star is estimated to be between 220 million and 300 million years. It is concluded that Alpha-2 CVn is old enough to have been magnetically braked to its current rotational velocity by either the centrifugal-wind or the accretion mechanism and to have developed its chemical peculiarities by either mechanism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 39; Apr. 197
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  • 107
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    Long chain carbon molecules and diffuse interstellar lines (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An estimate of the abundances of chain hydrocarbon molecules expected in dense interstellar clouds as a result of gas-phase chemistry alone supports the hypothesis that the long chain molecules are responsible for the diffuse interstellar lines seen in the optical spectra of stars lying behind fairly low-density interstellar clouds. In particular, it is shown that the equilibrium abundances of the long chain carbon molecules may remain quite high even for molecules with as many as 11 carbon atoms.
    Keywords: ASTROPHYSICS
    Type: Nature; 278; Apr. 19
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  • 108
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    On the charge polarization of cosmic systems (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The positive electric charge density associated with the internal electric fields of self-gravitating systems in hydrostatic equilibrium can be canceled by nearby external flowing plasmas, such as winds. For example, it can be shown that the positive electric charge of a star is likely to be completely screened by its stellar wind. Because winds and other nonstatic phenomena are widespread, the electrical polarization due to the positive charge on static systems such as stars should occur on relatively local scales, in contrast to the universal scale recently suggested by Bally and Harrison. The latter viewpoint would be correct only if the entire universe were in strict hydrostatic equilibrium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 109
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    Meridional circulation and CNO anomalies in red giant stars (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The possibility is investigated that meridional circulation driven by internal rotation might lead to the mixing of CNO-processed material from the vicinity of the hydrogen shell into the envelope of a red giant star. This theory of meridional mixing is found to be generally consistent with available data and to be capable of explaining a number of observational results without invoking a radical departure from the standard physics of stellar interiors. It is suggested that meridional circulation must be a normal characteristic of a rotating star and that meridional mixing provides a reasonable framework for understanding many of the CNO anomalies exhibited by weak-G-band and CN-strong stars as well as the low C-12/C-13 ratios measured among field red giants.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 110
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    Penrose pair production as a power source of quasars and active galactic nuclei (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Penrose pair production in massive canonical Kerr black holes (those with a/M equal to 0.998) is proposed as a way to explain the nature of the vast fluctuating energy production associated with active galactic nuclei and quasars. It is assumed that a Kerr black hole with a mass of the order of 100 million solar masses lies at the center of an active nucleus and that an accretion disk is formed. Penrose pair production in the inner ergosphere of such a massive canonical Kerr black hole is analyzed. The results indicate that: (1) particle pairs are ejected within a 40 deg angle relative to the equator; (2) the particle energy is of the order of 1 GeV per pair; (3) the pressure of the electron-positron relativistic gas is proportional to the electron-positron number density; (4) pair production may occur in bursts; and (5) the overall lifetime of an active nucleus would depend on the time required to exhaust the disk of its matter content. A test of the theory is suggested which involves observation of the 0.5-MeV pair-annihilation gamma rays that would be generated by annihilating particle pairs.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 229
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  • 111
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    GX339-4 - A new black hole candidate (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: HEAO-1 observations of aperiodic variability in the galactic X-ray source GX339-4 (4U 1658-48) on time scales of tens of milliseconds to a few seconds are reported. It is shown that the overall characteristics of GX339-4 place it in the same class of X-ray sources as Cyg X-1 and Cir X-1, which are candidates for black holes in binary systems. The detection of X-ray flares from GX339-4 is discussed, particularly a series of five sequential flares with separations of about 250 ms.
    Keywords: ASTROPHYSICS
    Type: Nature; 278; Mar. 29
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  • 112
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    The structure and evolution of X-ray clusters of galaxies (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The structure of clusters is described from observations at the Einstein Observatory. It was concluded that the nature of the X-ray emission is complex and varies from broad and highly clumped to smooth and centrally peaked. The clusters whose emission is clumped tend to be rich in spirals and to have X-ray temperatures in the few kilovolt range and low velocity dispersions. The smooth centrally peaked clusters are spiral poor, and have higher temperatures and larger velocity dispersions. For many of the clusters, the emission is irregular and cannot be described by the simple, spherically symmetric models for a hot isothermal or adiabatic gas. For these clusters, the low density, intracluster gas is influenced by the potential of individual bright galaxies.
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 409-421
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  • 113
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    The HEAO-1 neutron star timing experiment (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The HEAO-1 neutron star timing experiment is presented. The scientific motivation for the experiment, the reasons for the choice of Her X-1 and Vela X-1 as promising sources to study, the methodology, and the current status of the experiment are summarized.
    Keywords: ASTROPHYSICS
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 223-243
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  • 114
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    Velocity dispersions for X-ray-emitting clusters of galaxies (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Combining spectroscopy for five clusters of galaxies reported to contain X-ray sources with previously published data for 21 X-ray clusters, suggested correlations between the cluster's velocity dispersions and their X-ray properties have been tested. Unlike previous investigations, it is found that, for all reasonable data subsets, the cluster radial velocity dispersions sigma(r) are correlated with the cluster X-ray luminosities L/x/ at a confidence level exceeding 99%. The best-fit slope of the (log sigma/r/, log L/x/)-relation is somewhat larger than theoretically predicted, but accurate determination of that relation requires further X-ray and optical observations. For the 'most reliable' data subsample a correlation between sigma(r) and the X-ray source temperatures is also found but at a much lower confidence level (85%) than derived by previous investigators from smaller samples.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 115
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    Isotopes of titanium in cool stars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A program of stellar Ti isotopic-abundance determinations is described and related to changes that may have occurred in the Ti isotopic abundance ratios during the chemical evolution of the Galaxy, and to whether the abundance ratios are perturbed in the S and MS stars having atmospheres with enhanced abundances of s-process nuclei resulting from convective mixing after internal exposure to neutrons. High-resolution (0.07 A) Reticon spectra of portions of the TiO gamma (0,0), gamma (0,1), and delta (0,0) bands were the source material, and particular emphasis was placed on the definition of the continuum level. The isotopic abundance ratios are terrestrial in all of the sample, and errors in the (Ti-i)/(Ti-48) ratio are typically plus or minus 25% for the dwarfs and plus or minus 50% for the giants. The observations show that the magic nucleus Ti-50 is not enhanced in S and MS stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 116
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    Accretion by rotating magnetic neutron stars. III - Accretion torques and period changes in pulsating X-ray sources (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The solutions of the two-dimensional hydromagnetic equations are used to calculate the torque on a magnetic neutron star accreting from a Keplerian disk. It is found that the magnetic coupling between the star and the plasma in the outer transition zone is appreciable; that as a result, the spin-up torque on fast rotators is substantially less than that on slow rotators, and that for sufficiently high stellar angular velocities or sufficiently low mass accretion rates, the rotation of the star can be braked while accretion continues. These results are applied to pulsating X-ray sources, revealing that at high luminosities a star of given spin period rotating in the same direction as the disk can experience either spin-up or spin-down, depending on its luminosity. Also considered are the general problem of interpreting period changes in pulsating X-ray sources, and the dipole magnetic moments of nine pulsating X-ray sources are estimated by fitting the theoretical spin-up equation to estimates of the average luminosity and spin-up rate of each source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 117
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    Magnetic diffusion and ionization fractions in dense molecular clouds - The role of charged grains (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The physics of magnetic diffusion in dense molecular clouds is examined, with particular attention given to the role of charged grains in controlling the process. The ionization fraction of dense molecular clouds in the presence of grains is determined from considerations of charge exchange, dissociative recombination, radiative recombination and collisions between grains and charged species, and it is found that the inclusion of grains tends to lower the ionization fraction for a given cosmic-ray ionization rate and metal depletion. The kinematics of grain motion is discussed and it is shown that at temperatures less than 30 K, each grain alternates rapidly in charge between -1 and 0 and thus executes periodic motion in a self-gravitating cloud containing a magnetic field. The full kinematics of magnetic diffusion including the motions of ions and electrons are then examined, taking into account the additional viscous force from charged grains, and numerical calculations of the diffusion time scales of uniform, magnetically supported clouds or cloud cores are presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 118
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    Stellar atmosphere in statistical equilibrium (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A static atmosphere with only Lyman continuum radiation in radiative equilibrium is studied for the effects of radiative and collisional ionization on deviations from local thermodynamic equilibrium (LTE). Large increases and decreases of the kinetic temperature (range in T of about factor 2) and, correspondingly, very large over- and underpopulation of the bound state (range in b of about factor 1,000,000) are found, depending on the frequency dependence of the photoionization cross section. Despite these large deviations from LTE, which strongly modify the emergent spectrum, there is almost no effect on the particle densities, the degree of ionization, and the basic structure of the atmosphere.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 119
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    Iron and the formation of astrophysical dust grains (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Condensation of metallic iron or the iron carbide cohenite Fe3C is proposed as the source of the approximately 1000 K dust condensate in nova shells, Wolf-Rayet stars, and other objects. Iron grains may serve as nucleation sites for carbon in carbon-star ejecta; however, nucleation of graphite at its equilibrium saturation temperature is almost certainly kinetically inhibited. A gas phase rich in CO, C2H2, and HCN is produced instead.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 120
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    Gas-rich dwarfs and accretion phenomena in early-type galaxies (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An analysis is presented of the combined effects of cloud accretion and galactic winds and coronae. An accretion model is developed wherein gas-rich dwarf galaxies are accreted into galactic halos, which provides an adequate source of H I to account for observations of neutral gas in early-type galaxies. Accretion is found to fuel the wind, thereby regulating the accretion flow and yielding a time-dependent model for star formation, enrichment, and nuclear activity. The permissible parameter range for intergalactic gas clouds and galaxy groups is discussed, along with the frequency of gas-rich dwarfs and their large ratios of gas mass to luminosity. Also considered is the occurrence of gas stripping and the consequent formation of dwarf spheroidal systems that remain in the halo, and gas clouds that dissipate and suffer further infall. A cosmological implication of the model is that, because the characteristic time scale of a gas-rich dwarf galaxy to be accreted and lose its gas is comparable to a Hubble time, there may have been a far more extensive primordial distribution of such systems at earlier epochs.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 121
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    X-rays from Eta Carinae and the surrounding nebula (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Two X-ray pictures have been obtained of the Eta Car nebula using the imaging detectors of the Einstein Observatory. One covers a field 1-deg square with a resolution of 1 arcmin; the second covers a field 25 arcmin in diameter with resolution of a few arcsec. These show a region of diffuse X-ray emission with luminosity 10 to the 35th ergs/s. The sources have been positively identified as the peculiar object Eta Car, a Wolf-Rayet star, a cluster of O stars, and five individual O stars. The Eta Car X-ray source is extended and coincides with the outer shell of the diffuse object Eta Car itself. One X-ray bright spot may be emission from a central object within Eta Car.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 122
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    Viking relativity experiment - Verification of signal retardation by solar gravity (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Analysis of 14 months of data obtained from radio ranging to the Viking spacecraft verified, to an estimated accuracy of 0.1%, the prediction of the general theory of relativity that the round-trip times of light signals traveling between the earth and Mars are increased by the direct effect of solar gravity. The corresponding value for the metric parameter gamma is 1.000 plus or minus 0.002, where the quoted uncertainty, twice the formal standard deviation, allows for possible systematic errors.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 123
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    Detection of the 12.28 micron rotational line of molecular hydrogen in the Orion molecular cloud (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The pure rotational S(2) transition of molecular hydrogen at 12.28 microns has been detected in emission from the region of vibrational-rotational line emission in Orion. The line was resolved both spectrally and spatially, and the line shapes, widths, and velocities are consistent with those observed in the upsilon = 1-0 transitions. The results put new constraints on the structure, temperature, and dynamics of the region of molecular hydrogen emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 124
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    Electron-positron pair production in hot unsaturated Compton accretion models around black holes (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Electron-positron pairs photoproduced in conventional unsaturated Compton disk and spherical accretion models with electron temperature greater than 10 to the 9 K are found to dominate over the background electrons. This results in an equilibrium temperature lower than previously found and severely constrains the model parameters in some cases. Electron-positron pair production does not alleviate the thermal instability of the optically thin two-temperature disk model.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 125
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    Outer atmospheres of cool stars. II - Mg II flux profiles and chromospheric radiative loss rates (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: International Ultraviolet Explorer high-resolution spectra of the Mg II lines at 2796, 2803 A in 15 stars of spectral type G2-M2 including a wide range of luminosities are presented. These spectra are calibrated in absolute flux units at earth and at the stellar surface, and the chromospheric radiative loss rates in the Mg II lines are compared with corresponding rates in the Ca II H, K, and 8542 lines. The ratio of Mg II surface flux to total surface flux is found to be independent of stellar luminosity and thus gravity; may decrease slowly with decreasing effective temperature, and increases with decreasing period among RS Canum Venaticorum binaries. The factor of 10 range in this ratio at each effective temperature may be due to differences in the fractional surface area covered by plages and may indicate that stars of all luminosity classes have chromospheric plages. In this small data sample no evidence is found that the Mg II line surface fluxes indicate whether a star possesses a transition region and hot corona.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 126
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    The determination of electron abundances in interstellar clouds (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An independent method is proposed for the determination of electron abundances in dense clouds based upon the abundance ratio of HCO(+) and CO. The method is derived from a simple application of gas phase ion molecule interstellar chemistry. It is noted that unlike the fractionation of deuterated molecules, it applies to warm as well as to cool clouds. The method is illustrated with the results of the recent abundance survey of Wooten et al. (1978). Finally, it is shown that in cases where deuterium enhancement is measured, an upper limit can be obtained for the cosmic ray ionization rate.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 127
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    Mechanical heating of the interstellar medium. I - The source and rate (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper presents a model for the evolution of a supernova disturbance in the very low density, high temperature, interstellar matrix in order to explore consequences of such disturbances on the interstellar clouds. It is assumed that higher density material is sufficiently common to impede the velocity field, and that thermal conduction is magnetically quenched between the matrix and H I regions. An estimation is made of the work done by blast waves in compressing interstellar clouds, and it is shown that an individual disturbance is found to lose at least a modest fraction of its energy in this manner.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 128
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    Optical and X-ray properties of the newly discovered BL Lacertae object PKS 2155-304 /= H2155-304/ (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The soft X-ray source H 2155-304 has been precisely located with the HEAO 1 scanning modulation collimator, and identified with an object of bolometric magnitude approximately 14. The linear polarization, variability, spectrum, and diffuse image of the optical flux, together with the positional coincidence of the radio source PKS 2155-304, indicate that this object is a new member of the BL Lacertae class. Its characteristics are compared with those of other X-ray-emitting BL Lacertae objects, particularly Mrk 421.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 129
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    The Hercules supercluster. I - Basic data (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A sample of more than 150 redshifts, the majority new, is presented for galaxies brighter than an apparent photographic magnitude of 15.8 in a 28-square-deg field in Hercules containing the clusters A2151, A2152, and A2147. This sample populates a 60,000 cu Mpc conical volume. It contains a super-cluster centered near a radial velocity of 11,000 km/sec a large void of depth approximately 100 Mpc in front of the supercluster, and foreground structure at 4700 and 2300 km/sec the former associated with Seyfert's sextet.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 130
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    Origin of cosmic magnetic fields (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Reasons for describing cosmic hydromagnetic phenomena by introducing electric currents are summarized demonstrating that change from the traditional magnetic field description to a current description provides new aspects of cosmic electrodynamics. It is shown that the kink-instability of electric currents is the basic physical phenomenon responsible for magnetic flux generation in cosmic physics. A model which starts with a poloidal magnetic field is discussed; differential motions change the field configuration so that kinetic energy is transferred into magnetic energy of induced toroidal fields; the currents associated with these become unstable when the toroidal energy exceeds the poloidal energy resulting in an amplification of the original poloidal field.
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    Ultraviolet observations of interstellar molecules and grains from Spacelab (1979)
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    Publication Date: 2019-06-27
    Description: The paper presents observational results obtained on interstellar grains and molecules and suggests promising areas for Spacelab research. Regarding grains, useful data can be expected on the shape of the ultraviolet extinction curve for new interstellar regions, on the nature of UV extinction at short wavelengths, the presence of structure in the UV extinction curve comparable to the visible-wavelength diffuse bands, and the polarization properties of grains in UV wavelengths. The advances in observations of molecules will include the ability to prove more heavily-obscured regions, coverage of wavelength regions inadequately studied with previous instruments, and the capability of observing in optical absorption species detected in the same line of sight in radio emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science; 66; 2, De; Dec. 197
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  • 132
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    Lightman-Eardley instabilities and accretion disk thickening (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: After reviewing the role of Compton scattering in accretion disks around black holes, it is discussed whether Lightman-Eardley (LE) secular instabilities can trigger and maintain Pringle-Rees (PR) thermal instabilities. The radiative-transfer-equation and equation-of-state criteria for LE stability in alpha-viscosity-law disk models and dynamic viscosity criteria for more general situations is derived. On the basis of these considerations the LE instability is insufficient for inducing PR instabilities and hot thick inner regions important in accretion-disk models of compact hard X-ray sources. The density thinning due to radial velocity gradients in the accretion flow is suggested as a more likely and satisfactory mechanism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 20; 3, 19; 1979
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  • 133
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    Multiple scattering of solar resonance radiation in the nearby interstellar medium. I (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper presents approximate solutions obtained for a radiative transfer problem that represents a highly-idealized description of the multiple scattering of solar resonance radiation in the nearby interstellar medium. The problem of a point source in the center of a spherically symmetric cavity imbedded in an infinite uniform medium is solved for a range of cavity radii. First and second-order scattering contributions are calculated, and the Eddington approximation is used to estimate the higher order components of the radiation field. It is shown that for coherent scattering at very large cavity radii, the backscattered intensity from the cavity approaches three times the value deduced from the optically thin solution, in agreement with previous work. It is concluded that an accurate analysis of sky background will require including not only the frequency redistribution, but also the correct spatial distribution of density.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 80; 2, De; Dec. 197
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  • 134
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    Some problems of pulsar physics (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The theories of particle acceleration along polar field lines are reviewed, and the total energization of the charge separated plasma is summarized, when pair creation is absent. The application of these theories and plasma supply to pulsars is discussed, with attention given to the total amount of electron-positron plasma created and its momentum distribution. Various aspects of radiation emission and transport are analyzed, based on a polar current flow model with pair creation, and the phenomenon of marching subpulses is considered. The coronation beaming and the relativistically expanding current sheet models for pulsar emission are also outlined, and the paper concludes with a brief discussion of the relation between the theories of polar flow with pair plasma and the problem of the energization of the Crab Nebula.
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  • 135
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    Pulsar magnetospheres (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The structure of both the interior and exterior pulsar magnetosphere depends upon the strength of its plasma source near the surface of the star. We review magnetospheric models in the light of a vacuum pair-production source model proposed by Sturrock, and Ruderman and Sutherland. This model predicts the existence of a cutoff, determined by the neutron star's spin rate and magnetic field strength, beyond which coherent radio emission is no longer possible. The observed distribution of pulsar spin periods and period derivatives, and the distribution of pulsars with missing radio pulses, is quantitatively consistent with the pair production threshold, when its variation of neutron star radius and moment of inertia with mass is taken into account. All neutron stars observed as pulsars can have relativistic magnetohydrodynamic wind exterior magnetospheres. The properties of the wind can be directly related to those of the pair production source. Radio pulsars cannot have relativistic plasma wave exterior magnetospheres. On the other hand, most erstwhile pulsars in the galaxy are probably halo objects that emit weak fluxes of energetic photons that can have relativistic wave exterior magnetospheres. Extinct pulsars have not been yet observed.
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  • 136
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    The IR energy distribution of SS433 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The infrared energy distribution of the emission-line object SS 433 in the range 1 to 10 microns is determined. Photometric measurements were made with a 2.2-m telescope using an InSb detector and a 6-arcsec diaphragm for 1.2- to 4.8-micron observations and a gallium-doped germanium bolometer with a 6-arcsec diaphragm for 8- to 13-micron observations. Results indicate the presence of substantial night-to-night flux density and color variations, and a decrease in flux density at wavelengths greater than 5 microns. The energy cut-off is used to estimate a physical size of 1 AU for the emitting region and an electron density of 10 to the 11th/cu cm on the basis of a model of reddened free-free emission from an ionized plasma, with self-absorption of radiation over 5 microns. The greater variability observed at longer wavelengths is also interpreted in terms of this model.
    Keywords: ASTROPHYSICS
    Type: Nature; 282; Dec
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  • 137
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    X and UV radiation from accreting magnetic degenerate dwarfs (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 138
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    Imaging X-ray observations and the temperature structure of the Cygnus Loop (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Imaging X-ray observations of the northeast portion of the Cygnus Loop (NGC 6992) reveal that X-ray emission extends 5 arc min beyond the optical filaments. Comparison with Fe XIV 5303 forbidden line measurements across the emitting shell is consistent with a temperature gradient across the shell from 10 to the 6.1 K (outside) to 10 to the 6.3 K (inside). Both X-ray and Fe XIV forbidden line intensity and spatial structure can be explained by a Sedov adiabatic blast wave with a shock velocity of 290 plus or minus 15 km/s.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 139
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    HEAO 1 observations of X-ray emission from flares on dMe stars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper reports the detection of two X-ray flares from each of the nearby dMe stars, AT Mic and AD Leo, with the A-2 experiment on board HEAO 1. A spectrum obtained during the brighter AT Mic flare, the first X-ray spectrum of a stellar flare, is well matched by a thermal model with a temperature 3 x 10 to the 7 K and an iron K-alpha emission line. The X-ray luminosities derived are in the range 1.3-16 x 10 to the 30th ergs/s, while emission measures are in the range 1.1-14 x 10 to the 53rd/cu cm. The estimated Lx/Lopt ratios exceed unity and are inconsistent with Mullan's flare model. Several scenarios to explain this discrepancy are proposed.
    Keywords: ASTROPHYSICS
    Type: PB80-221559 , Astrophysical Journal; vol. 234
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  • 140
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    The hydrodynamics of off-center explosions (1979)
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    Publication Date: 2019-06-27
    Description: The behavior of off-center supernova explosions is investigated using a two-dimensional hydrodynamic code. An important application of these calculations is the possible formation of high-velocity pulsars. The dependence of the final velocity of the collapsed remnant on the location and energy of the explosion is computed. The largest remnant velocities result from explosions located at a mass fraction of 0.5. An explosion energy 50% greater than the binding energy of the star ejects 0.51 solar masses, producing a 1.4 solar mass remnant with a velocity of 400 km/s. However, this energy must be generated in a very small region of the star in order to create the required asymmetry in the explosion. Because of this, a specific energy of about 10 to the 20th ergs/g is needed. Nuclear reactions can produce no more than about 5 x 10 to the 17th erg/g, and it is unclear how the energy produced in gravitational collapse models can be sufficiently localized. Unless a supernova mechanism can be found which can produce enough energy in a small region of the star, off-center explosions do not provide a satisfactory explanation for high-velocity pulsars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 141
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    Positron production by pulsars (1979)
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    Publication Date: 2019-06-27
    Description: Analytical calculations based on the 'polar-cap light-cylinder' (PCLC) (Sturrock, 1971a) and 'polar-cap force-balance' (PCFB) (Roberts and Sturrock, 1972,3) pulsar models show that in either case the intensity of the 511 keV gamma-ray line from the galactic center can be explained as the result of the annihilation of positrons produced by pulsars. The Crab pulsar (braking index approximately 2.5) is estimated to have a power budget of 10 to the 38th ergs/s, and to produce a total number of 10 to the 51.7th positrons. It is suggested that positron annihilation can be supplied by pulsars if the birthrate of pulsars in the galactic center is 10 to the -8.2nd/s.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 142
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    Possible observational constraints on the mass-radius relation of neutron stars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The effect of gravitational redshift on the blackbody radii, as deduced from the tails of X-ray bursts, is considered. Observed values of blackbody radii put an upper limit to the mass and constrain the mass-radius relations of neutron stars. Possible consequences for the equation of state of high-density matter are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 143
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    A spectroscopic study of the optical counterparts of three X-ray bursters (1979)
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    Publication Date: 2019-06-27
    Description: One of the major puzzles in galactic X-ray astronomy is the nature of the galactic bulge sources in general and the X-ray burst sources in particular. The answer to this puzzle is likely to come from studies of the faint blue optical counterparts which have been identified with several of these sources. As part of such a study, some results of a detailed investigation of the spectroscopic properties of the optical counterparts to three X-ray bursters - 4U 1735-44, 4U 1636-53, and MXB 1659-29.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 144
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    Model emission spectra from primeval galaxies (1979)
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    Publication Date: 2019-06-27
    Description: The paper computes models of the UV luminosity produced by a distribution of supernova remnants resulting from a burst of star formation in primeval galaxies at large redshift. The evolution of low metal abundance remnants is described analytically, and their UV emission is found from a velocity grid of radiative shock models. The implications of these results for the detection of line emission from young galaxies and for the diffuse background radiation are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 145
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    Infrared spectra of IC 418 and NGC 6572 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Spectrophotometric observations from 2 to 4 and 8 to 13 microns of NGC 6572 and from 4 to 13 microns of IC 418 are reported. Also reported are observations of the size of IC 418 in the optical and at 1.65 and 2.2 microns. Both planetary nebulae emit more radiation than expected from recombination at wavelengths longer than -4 microns; this radiation is attributed to heated dust. The spectra show a plateau from 10.5 to 13 microns, and this peak is tentatively attributed to emission from large silicon carbide particles. Fine-structure emission lines are also discussed; the presence of (forbidden Ar III) but not (forbidden Ne II) in NGC 6572 suggests that ions having the same ionization potential can nevertheless have different fractional abundances.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 146
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    Stellar model chromospheres. XI - A survey of Ca II lambda 8542 line profiles in late-type stars of differing chromospheric activity (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: PB80-144215 , Astrophysical Journal Supplement Series; 41; Nov. 197
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  • 147
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    Molecule formation and infrared emission in fast interstellar shocks. I Physical processes (1979)
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    Publication Date: 2019-06-27
    Description: The paper analyzes the structure of fast shocks incident upon interstellar gas of ambient density from 10 to the 7th per cu cm, while focusing on the problems of formation and destruction of molecules and infrared emission in the cooling, neutral post shock gas. It is noted that such fast shocks initially dissociate almost all preexisting molecules. Discussion covers the physical processes which determine the post shock structure between 10 to the 4 and 10 to the 2 K. It is shown that the chemistry of important molecular coolants H2, CO, OH, and H2O, as well as HD and CH, is reduced to a relatively small set of gas phase and grain surface reactions. Also, the chemistry follows the slow conversion of atomic hydrogen into H2, which primarily occurs on grain surfaces. The dependence of this H2 formation rate on grain and gas temperatures is examined and the survival of grains behind fast shocks is discussed. Post shock heating and cooling rates are calculated and an appropriate, analytic, universal cooling function is developed for molecules other than hydrogen which includes opacities from both the dust and the lines.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 41; Nov. 197
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  • 148
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    X-ray and optical variability in 2A1052+606 - A new RS CVn-type system (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper discusses a star with RS CVn-type characteristics discovered as a result of an accurate X-ray location. The RS CVn binaries have been found to be a new class of soft X-ray sources from the HEAO 1 low energy sky survey. The source was detected at energies below 1 keV and evidence is presented for variability on time scales of approximately 1 day. The strong soft X-ray source was observed at a position consistent with 2A1052+606 and the X-ray light curve shows that the source underwent a strong soft X-ray flare. Subsequent spectrophotometry revealed variable H(alpha) and possibly CaII H,K emission which strongly supports its classification as an RS CVn system.
    Keywords: ASTROPHYSICS
    Type: Nature; 282; Dec. 13
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  • 149
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    Optical spectrophotometry of comet Tempel 2 far from the sun (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: With the advent of mission planning for spacecraft encounters with comets in the 1980s, the lack of basic data on cometary nuclei has become quite apparent and a real problem. More effort is needed on all comets, with special attention given to probable space flight targets such as Tempel 2. The paper presents medium-spectral-resolution spectrophotometry of P/Tempel 2, made at heliocentric distances of 2.66 and 3.02 AU on two dates in 1978. It is shown that optical spectrophotometry of comet Tempel 2 near 3 AU heliocentric distance places strict limits on its activity, the modeled CN production rate having an upper limit of 6 times 10 to the 21st molecules per sec. The observations of P/Tempel 2 are compatible with a bare nucleus of 1.6 km radius (geometric albedo = 0.15) and somewhat redder than the sun.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 91
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  • 150
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    Gravitational waves from rotating and precessing rigid bodies - Simple models and applications to pulsars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An axially symmetric, torque-free rigid body, rotating and precessing, emits gravitational quadrupole radiation at two frequencies, omega and 2 omega, corresponding to the l = 2, m = 1,2 spherical harmonics. The paper presents explicitly the waveforms of the two polarizations at both frequencies. From observations of gravitational waves, one can derive information about the body's orientation and its precession amplitude. Electromagnetic radiation emitted by a spot fixed on the surface of the body arrives in pulses at a mean frequency Omega which is typically different from omega. If the body is not axially symmetric but the amplitude of the precession is small, the gravitational radiation at the lower frequency omega is split into two frequencies on either side of the electromagnetic pulse frequency. Explicit waveforms for the two polarizations in this case are also presented.
    Keywords: ASTROPHYSICS
    Type: Physical Review D - Particles and Fields; vol. 20
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  • 151
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    Soft X-ray observation of the Rho Ophiuchus dark cloud region (1979)
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    Publication Date: 2019-06-27
    Description: Soft X-rays (0.1-0.8 keV) from the region including the Rho Oph dark cloud were observed with the SAS-3 low-energy X-ray telescope. No X-ray absorption by the cloud was observed. This indicates that the diffuse component of soft X-rays in this region is mostly from the foreground of the Rho Oph cloud which is located at a distance of 160-200 pc.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science; 65; 2, Oc; Oct. 197
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  • 152
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    The thermodynamics of dust formation - Evidence from meteorites (1979)
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    Publication Date: 2019-06-27
    Description: The paper examines the thermodynamics of dust formation indicated by meteorites. Much of interstellar dust probably formed in the nebulae around protostars, and mineralogy and composition of meteorites provides information that prevailed in the nebula. The fact that the gas associated with interstellar dust has solar H/S ratios indicates that FeS, which forms at 680 K, is not present in the dust, and since iron only becomes oxidized at even lower temperatures, oxidized iron is not expected in the dust. If most interstellar dust forms in the nebulae and is ejected back in space, a high temperature is indicated. High-temperature fractionation processes played an important role in the nebula, and much of the Al, Ca, and Ti evidently condensed and accreted into cm-sized objects, some of which are found in carbonaceous chondrites; they are explicable in terms of formation from a cooling neutral gas with cosmic composition.
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  • 153
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    A reconsideration of nucleation phenomena in light of recent findings concerning the properties of small clusters, and a brief review of some other particle growth processes (1979)
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    Publication Date: 2019-06-27
    Description: The paper examines mechanisms of nucleation and growth by condensation and coagulation in the light of recent research on properties of small clusters. Homogeneous, hetero-molecular, and heterogeneous nucleation is analyzed, and expressions for the rate of formation of a stable condensed phase and evaluation of the free energy of formation of charged droplets are given. Application of high-pressure mass spectrometry which makes possible a direct determination of intensity spectra for cluster distributions, measurement of the thermodynamic properties of individual ion clusters and determination of cluster entropy and bond energy is discussed. Finally, coagulation of the condensed phase is considered, noting that concentration and mean particle size vary during coagulation, but the shape distribution is time independent, leading to the concept of a self-preserving aerosol size distribution.
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  • 154
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    X-ray observations of the 5 March 1979 gamma-burst field (1979)
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    Publication Date: 2019-06-27
    Description: An extremely intense burst of hard X-rays and gamma-rays that was recorded by the nine interplanetary spacecraft of the burst sensor network and localized by time-of-flight determinations to a position coincident with the supernova remnant N49 in the Large Magellanic Cloud is analyzed. The region of the sky was observed both before and after the gamma-ray event with the soft X-ray imaging instruments aboard the Einstein Observatory. Coupled with the optical plate material, the soft X-ray data is used to place severe constraints on models for the origin of the transient phenomena.
    Keywords: ASTROPHYSICS
    Type: Nature; 282; Dec. 6
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  • 155
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    Observation of soft X-ray emission from the supernova remnant HB9 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The number of known X-ray emitting supernova remnants in our galaxy has significantly grown as a result of the soft X-ray survey by the HEAO-1 spacecraft. The HEAO-1 A-2 experiment has observed soft X-ray emission from the old supernova remnant HB9 which lies close to the previously identified X-ray source, Capella. Spectral data and the low optical obscuration in the direction of the remnant suggest that HB9 is a good candidate for detecting Fe XIV coronal forbidden-line emission. Mapping of the coronal line emission in association with the imaging X-ray data expected from HEAO-2 would allow the temperature profile of the emitting shell to be determined in a manner similar to that used by Tuohy, Nousek, and Garmire (1979) for the Cygnus Loop, which is in a similar evolutionary phase to HB9.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 189
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  • 156
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    Supernovae and the origin of the solar system (1979)
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    Publication Date: 2019-06-27
    Description: This review concentrates on recent ideas involving a relationship between the early solar system and supernova explosions. It summarizes briefly the data that has helped inspire those ideas. Because the true relationship is still unknown and generates controversy, the distinct ideas are introduced singly in the historical context of their origins, and the active sense of surprise and controversy is visible. Quotations from pivotal papers are used as part of the exposition. The subject involves equally the isotopic anomalies detected in meteorites and the dynamic events of galactic evolution, nucleosynthesis, and protosolar collapse. Whatever the correct situation is, new connections have been found between the origin of the elements and the formation of the solar system. The objective of this review is to enable interested space scientists to quickly identify the competing points of view and the experiments and theories that have led to them.
    Keywords: ASTROPHYSICS
    Type: Space Science Reviews; 24; Oct. 197
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  • 157
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    A form-factor method for determining the structure of distorted stars (1979)
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    Publication Date: 2019-06-27
    Description: The equilibrium equations of a uniformly rotating and tidally distorted star are reduced to the same form as for a spherical star except for the inclusion of two form factors. One factor, expressing the buoyancy effects of centrifugal force, is determined directly from the integrated structure variables. The other factor, expressing the deviation from spherical shape, is shown to be relatively insensitive to errors in the assumed shape, so that accurate solutions are obtained in spite of the use of an a priori shape. The method is employed by adding computations for the factors to an existing spherical model program. Upper Main Sequence models determined by this method compare closely with results from the double approximation method even for critical rotation and tidal distortion.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science; 64; 2, Au; Aug. 197
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  • 158
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    Dust in cosmic plasma environments (1979)
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    Publication Date: 2019-06-27
    Description: Cosmic dust is invariably immersed in a plasma and a radiative environment. Consequently, it is charged to some electrostatic potential which depends on the properties of the environment as well as the nature of the dust. This charging affects the physical and dynamical properties of the dust. In this paper the basic aspects of this dust-plasma interaction in several cosmic environments - including planetary magnetospheres, the heliosphere and the interstellar medium - are discussed. The physical and dynamical consequences of the interaction, as well as the pertinent observational evidence, are reviewed. Finally, the importance of the surface charge during the condensation process in plasma environments is stressed.
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  • 159
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    The X-ray spectrum of the BL Lacertae object PKS 0548-322 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: X-ray observations of H0548-322 = PKS 0548-322 at energies from 0.15 keV to 24 keV with the HEAO A-2 experiment are reported. The spectrum shows a distinct break in slope near 2 keV, with the indices of power-law energy spectra of 2.2 below and 0.3 above this break. A synchrotron self-Compton model is consistent with radio, optical, and all X-ray data, although a modified synchrotron self-Compton model with added thermal origin for the low-energy X-ray spectrum is also plausible.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 160
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    Far-infrared observations of M17 - The interaction of an H II region with a molecular cloud (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 161
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    Interplanetary dust (1979)
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    Publication Date: 2019-06-27
    Description: Progress in the study of interplanetary dust during the past four years is reviewed. Attention is given to determinations of the relative contributions of interstellar dust grains, collisional debris from the asteroid belt and short-period comets to the interplanetary dust cloud. Effects of radiation pressure and collisions on particle dynamics are discussed, noting the discovery of the variation of the orbital parameters of dust particles at 1 AU with size and in situ measurements of dust density between 0.3 and 5 AU by the Helios and Pioneer spacecraft. The interpretation of the zodiacal light as produced by porous absorbing particles 10 to 100 microns in size is noted, and measurements of the Doppler shift, light-producing-particle density, UV spectrum, photometric axis and angular scattering function of the zodiacal light are reported. Results of analyses of lunar rock microcraters as to micrometeoroid density, flux rate, size distribution and composition are indicated and interplanetary dust particles collected from the stratosphere are discussed. Findings concerning the composition of fragile meteoroid types found as cosmic spherules in deep sea sediments are also presented.
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  • 162
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    Extended-bandwidth X-ray observations of Cygnus X-1 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An energy- and time-resolved observation of Cyg X-1, sensitive from 0.15 to 20 keV, is reported which was performed to investigate the spectrum and time variability of the flux at low X-ray energies. Data in the band from 1.5 to 42 keV, obtained in two previous rocket flights, are reanalyzed to search for any energy dependence of the time signature. No such energy dependence is found, so the explanation of the observed low-energy excess of Cyg X-1 as emission from an extended region separate from the high-energy source is rendered untenable. The evident stability of the power-law spectrum of Cyg X-1 through the observed shot-noise variation is shown to suggest that the spectrum has a Comptonization origin. It is concluded that there is no obvious analogy to be made between Cyg X-1 and X-ray bursters.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 163
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    The spectral and spatial distribution of radiation from Eta Carinae. II High-resolution infrared maps of the Homunculus (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The spectral and spatial distribution of radiation from Eta Carinae II and high-resolution infrared maps of the Homunculus are presented. It is found that at the resolution of 1.1 arcsec the source is resolved into two intensity peaks at four wavelengths from 3.6 to 11.2 microns. The separation of the two peaks with wavelength is discussed, concluding that they are produced by an asymmetrical distribution of dust formed by extensive mass loss from the central source. The extension of the wings of the source at various wavelengths provide confirmatory evidence for an enrichment of a grain species such as corundum, relative to silicate material in the outer regions of the source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 164
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    The spectrum of the Becklin-Neugebauer source in Orion from 3.3 to 5.5 microns (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Spectra of the Becklin-Neugebauer source in Orion and the associated nebula are presented covering the complete range from 3.3-5.5 microns with a resolution of 1.2 kaysers. The data were taken in December 1976 and February 1978. Atomic hydrogen emission lines of Brackett-alpha and Pfund-beta are seen, as well as molecular CO absorptions. No other features intrinsic to BN were detected. The December 1976 data show an anomalously high intensity for Pfund-beta line. Theoretical considerations are presented which suggest that Pfund-beta radiation arises in a small dense region, with the transition possibly lasing.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 165
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    On the energy distribution in Sirius B (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A spectrum of Sirius B in the wavelength region 1100-1900 A taken with the IUE satellite shows an absolute flux and spectral energy distribution in the continuum in agreement with theoretical white-dwarf models with T(eff) of 26,000 K plus or minus 1000 K for log g equals 8.65 and R equals 5.08 x 10 to the 8th cm. The Lyman-alpha profile is also in agreement with these parameters. No obvious emission lines in the spectrum of Sirius B or A which could indicate the presence of a chromosphere or corona in either of the stars are observed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 166
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    Isotopic anomalies from neutron reactions during explosive carbon burning (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The heavy isotopic anomalies observed recently in the fractionation and unknown nuclear inclusions from the Allende meteorite are explained by neutron reactions during the explosive carbon burning (ECB). This model produces heavy anomalies in the same zone where Al-26 and O-16 are produced, thus reducing the number of source zones required for the isotopic anomalies. Unlike the classical r-process, the ECB n-process avoids the problem with the Sr anomaly and may resolve the problem of conflicting time scales between Al-26 and the r-process isotopes I-129 and Pu-244. Experimental studies of Zr and Ce isotopic composition are proposed to test this model.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 167
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    The luminosity function of galaxy systems - From single galaxies and small groups to rich clusters (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The luminosity function (LF) of galaxy systems is determined, from single galaxies and small groups to rich clusters. The LF of rich (Abell) clusters is found to be a steeply decreasing function of cluster number density with cluster luminosity, and the groupings LF (that is, groups to rich clusters) can be well represented by a Schechter-type (1976) analytic form. The general LF of all galaxy systems is also found to be a smooth and steeply decreasing function of number density with luminosity, exhibiting an exponential cutoff in the rich-cluster luminosity domain, a power law dependence over most of the intermediate luminosity range, and a flattening of slope below the characteristic galactic luminosity. Comparisons of the LF with the LF of galaxies and X-ray clusters of galaxies are also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 168
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    A further study of the Comptonization of X-rays by low-temperature electrons (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The hard X-ray transfer problem is considered for a monochromatic point source at the center of a spherical cloud of Compton scatterers. The problem is solved by a Monte Carlo calculation which provides solutions accurate to within a few percent with a reasonable amount of computation. It is shown that the method proposed by Illarionov et al. (1979) makes some significant errors when applied to atmospheres with a Thompson depth of 3. It is demonstrated that second-order corrections to the cross section are important at 50 keV, while first-order corrections are important even at 7 keV.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 232
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  • 169
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    A search for stellar remnants of supernovae (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The slitless spectra of the stars in the central regions of six galactic supernova remnants Cas A, Kepler, Tycho, SN 1006, RCW 86, and the Cygnus Loop were obtained with the prime focus transmission gratings at the 4M telescopes on Kitt Peak and Cerro Tololo. It was found that no stellar remnant with an unusually blue or peculiar spectrum is present in any of the remnants down to the limit of m sub pg of 18.5. Except for the Cygnus Loop, the area searched in each remnant is large enough that objects with transverse velocities of 1000 km/s would be well within the field. The results are also compared with a computation of emission from gas near a neutron star and with the unpulsed emission from the Crab pulsar; in both cases upper limits were set which place constraints on a possible condensed stellar remnant.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 170
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    Evidence for a carbon-rich dust cloud in front of HD 193793 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The wavelength dependence of the interstellar extinction toward HD 193793 is shown to be anomalous. Although radiative transfer effects could play a role, it is shown that relatively small graphite grains forming in the stellar wind can explain the observations if the particles are slowed down by the interstellar medium at a distance of less than about 10 million solar radii from the star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 171
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    Supernova remnants in the Large Magellanic Cloud (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: X-ray emission from 10 previously identified supernova remnants (SNR) in the Large Magellanic Cloud has been discovered in a partially completed survey of this nearby galaxy with the imaging proportional counter on the Einstein Observatory. The X-ray luminosities (0.5-3.0 keV) of these remnants range from 3 x 10 to the 35th to 4 x 10 to the 37th ergs/s. N157B and N158A, whose identifications as SNR were previously based solely on their radio spectra, have been detected as strong X-ray emitters. Two other objects from an optically selected list of candidate SNR were found to coincide with X-ray sources and therefore probably are SNR. The value of obtaining such a uniform sample of SNR at a known distance is illustrated by comparing the properties of the remnants and by fitting standard evolutionary models to the results.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 172
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    High-resolution X-ray observations of the Cassiopeia A supernova remnant with the Einstein Observatory (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Cas A was observed with the imaging detectors on the Einstein X-ray Observatory. The mass of the expanding shell due to the interaction of the blast wave and the ambient medium is determined. This indicates that Cas A is probably not in the free expansion phase, but has not yet reached the adiabatic phase of expansion. Detailed comparison of X-ray, optical, and radio images shows various degrees of correlation, indicating that several processes for emission are present. An upper limit of 1,500,000 K is established for any stellar remnant that is below the expected temperature of a neutron star by a factor of about 5. The total mass of the SNR is found to be 10-30 solar masses
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 173
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    High-resolution X-ray spectroscopy of M87 with the Einstein observatory - The detection of an O VIII emission line (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper deals with high-resolution X-ray spectroscopy performed to study the extended source surrounding the giant elliptical galaxy, M87, in the Virgo cluster. From observations carried out with a focal plane crystal spectrometer, L-alpha emission was detected from hydrogenic oxygen (O VIII). Upper limits could be set on lines from intermediate ionization states of iron. The presence of a quantity of cooler matter surrounding M87 was revealed, which has important implications for cluster models and favors a radiatively controlled accretion mechanism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 174
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    X-ray observations of galaxies in the Virgo cluster (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: X-ray emission from individual galaxies (other than M87) in the Virgo cluster has been detected using observations from the Einstein X-ray Observatory. One of the galaxies, M86, exhibits extended emission which is interpreted as thermal bremsstrahlung from hot gas being stripped from the galaxy by the ram pressure of the intracluster medium. The observations are discussed in relation to models for the dynamical evolution of clusters of galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 175
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    Einstein observations of the X-ray structure of Centaurus A - Evidence for the radio-lobe energy source (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The X-ray source at the center of the radio galaxy Centaurus A has been resolved into the following components with the imaging detectors on board the Einstein X-ray Observatory: (1) a point source coincident with the infrared nucleus; (2) diffuse X-ray emission coinciding with the inner radio lobes; (3) a 4-arcmin extended region of emission about the nucleus; and (4) an X-ray jet between the nucleus and the NE inner radio lobe. The 2 x 10 to the 39th ergs/s detected from the radio lobes probably arises from inverse Compton scattering of the microwave background. The average magnetic field in the SW lobe is determined to be not less than 4 microgauss. The extended region may be due to emission by a cloud of hot gas, cosmic-ray scattering, or stellar sources. The jet provides strong evidence for the continuous resupply of energy to the lobes from the nucleus.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 176
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    X-ray studies of quasars with the Einstein Observatory (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results of an investigation of the X-ray properties of quasars conducted using the Einstein Observatory (HEAO 2) are reported. The positions, fluxes and luminosities of 35 known quasars were observed by the Einstein high-resolution imaging detector and the imaging proportional counter. Assuming optical redshifts as valid distance indicators, 0.5-4.5 keV X-ray luminosities ranging from 10 to the 43rd to 10 to the 47 ergs/sec are obtained, with evidence of very little cold gas absorption. Flux variability on a time scale of less than 10,000 sec is observed for the quasar OX 169, which implies a mass between 8 x 10 to the 5th and 2 x 10 to the 8th solar masses for the black hole assumed to be responsible for the emission. Preliminary results of the quasar survey also indicate that quasars contribute significantly to the diffuse X-ray background.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 177
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    Streaming of interstellar grains in the solar system (1979)
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    Publication Date: 2019-06-27
    Description: Results of a theoretical study of the interactions between interstellar grains streaming through the solar system and the solar wind are presented. It is shown that although elongated core-mantle interstellar particles of a characteristic radius of about 0.12 microns are subject to a greater force due to radiation pressure than to gravitational attraction, they are still able to penetrate deep inside the solar system. Calculations of particle trajectories within the solar system indicate substantial effects of the solar activity cycle as reflected in the interplanetary magnetic field on the distribution of 0.12- and 0.0005-micron interstellar grains streaming through the solar system, leading to a 50-fold increase in interstellar grain densities 3 to 4 AU ahead of the sun during years 8 to 17 of the solar cycle. It is noted that during the Solar Polar Mission, concentrations are expected which will offer the opportunity of detecting interstellar grains in the solar system.
    Keywords: ASTROPHYSICS
    Type: Nature; 282; Nov. 15
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  • 178
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    An absorption feature in the spectrum of the pulsed hard X-ray flux from 4U0115 + 63 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A spectral feature, apparently an absorption line, has been observed at an energy of 20.1 + or - 0.5 keV in the pulsed flux of the 3.61-s X-ray pulsar 4U 0115+63 by using the UCSD/MIT instrument on HEAO 1. The line strength, expressed as equivalent width, is 3.1 + or - 0.5 keV. Although essentially unresolved, the feature has a depth more than 60% of the continuum flux. If the feature arises by cyclotron resonance absorption near the magnetic poles of the neutron star, it implies a magnetic field of between approximately 1.8 and 2.5 x 10 to the 12th G, depending on the gravitational redshift (no more than about 5-40%).
    Keywords: ASTROPHYSICS
    Type: Nature; 282; Nov. 15
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  • 179
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    Ultraviolet scattering properties and the size distribution of interstellar grains (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
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  • 180
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    Sudden grain nucleation and growth in supernova and nova ejecta (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The thermal conditions leading to the rapid nucleation and growth of dust in astronomical explosions are examined. The contribution to nucleation physics lies only in the clarification of the ambient conditions where it apparently occurs. In both nova and interior shells of supernovae, dust precipitates in gas densities of the order of 10 to the -14th g/cu cm a few months after the explosion. The ambient conditions differ widely, however. Supernova condensation occurs in a thermal equilibrium, with photons, ions, electrons, and grains having equal temperatures. In novae huge disequilibria exist, with photon and electron temperatures near 50,000 K, photon energy density near 750 K, and forming refractory grains near 1800 K. In neither type of explosion can the condensed matter easily maintain chemical equilibrium with the total system. Interesting isotopic anomalies are trapped in both types of refractory condensate in the interstellar medium. The nova provides the best astronomical laboratory for observing the condensation.
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  • 181
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    Relativistic blast waves in two dimensions. I - The adiabatic case (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Approximate solutions are presented for the dynamical evolution of strong adiabatic relativistic blast waves which result from a point explosion in an ambient gas in which the density varies both with distance from the explosion center and with polar angle in axisymmetry. Solutions are analytical or quasi-analytical for the extreme relativistic case and numerical for the arbitrarily relativistic case. Some general properties of nonplanar relativistic shocks are also discussed, including the incoherence of spherical ultrarelativistic blast-wave fronts on angular scales greater than the reciprocal of the shock Lorentz factor, as well as the conditions for producing blast-wave acceleration.
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  • 182
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    The excitation of density waves at the Lindblad and corotation resonances by an external potential (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The linear response of a differentially rotating two-dimensional gas disk, both with and without self-gravity, to a rigidly rotating external potential is calculated on the assumptions that the speed of sound is much smaller that the orbital velocity and that the external potential varies on the scale of the disk radius. The results show that: (1) the external potential exerts torques on the disk only at the Lindblad and corotation resonances; (2) the torque is positive at the outer Lindblad resonance and negative at the inner Lindblad resonance; (3) the torque at corotation has the sign of the radial vorticity gradient; and (4) the torques are of the same order of magnitude at both types of resonance and independent of the speed of sound in the disk. It is found that the external potential also excites density waves in the vicinity of the Lindblad and corotation resonances, that the long trailing wave is excited at a Lindblad resonance, and that short trailing waves are excited at the corotation resonance. The behavior of particle disks is briefly discussed, and the external torques on particle disks are proven to be identical to those on gas disks
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  • 183
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    Spectrophotometry of Michigan-Tololo quasars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The Michigan-Tololo sample of quasars is discussed using observational data for 48% of this sample. Emission-line quasar characteristics are confirmed for 80% of the objects observed, including at least four new quasars with spectral features indicative of 'supernova-like' outflow. Approximately 73% of the redshifts predicted from the discovery plates are found to be accurate, with a mean error in z of 0.03; a large range of z (from about 0.1 to 3.16) is represented in the sample. The interpretation of the observed redshift distribution for quasars is strongly dependent upon the significance ascribed to wavelength-dependent selection effects. It appears that the behavior of the comoving quasar density above z = 2.0 may be represented by a constant or an exponential increase.
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  • 184
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    Primordial inhomogeneities in the expanding universe. III - The density velocity distributions in cluster halos as a cosmological probe (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
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  • 185
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    Optical studies of the Seyfert 2 X-ray galaxy NGC 2110 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Spectrophotometry of the nucleus of the X-ray galaxy NGC2110 shows a typical Seyfert Type 2 spectrum with a strong galactic continuum. The widths of the forbidden lines are about 360 km/s (FWHM), H-beta being somewhat broader. The moderate Balmer decrement implies that the interstellar reddening is approximately 2.1 mag. The average electron density and temperature in the line-emitting region are approximately 300 per cu cm and 35,000 K, respectively. From measurements of the nebulium line, it is found that the extent of the nucleus measured along the major axis of the galaxy is about 10 arcsec (2100 pc) and the full range of gas velocities is about 700 km/s. A direct plate is discussed which shows faint spirallike features in NGC2110, a galaxy currently classified as elliptical. NGC2110 is a member of a new class (about 5 members) of very nearby (cz less than 2500 km/s) X-ray galaxies. Bradt et al. (1978) tentatively concluded that they are Seyfert Type 2 galaxies. This conclusion is supported, and it is shown that this is not inconsistent with the narrowness (less than 500 km/s FWHM) of their emission line.
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  • 186
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    Chromospheres of the active dwarf binaries EQ Pegasi and Xi Bootis (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Ultraviolet spectroscopic measurements of the M dwarf binary EQ Peg and the G8 V star Xi Boo A have been made with the International Ultraviolet Explorer satellite. High-temperature emission lines (N V, C IV, Si IV) are present with similar strengths in both stars. The surface fluxes of chromospheric and transition-region lines are enhanced relative to those of normal main-sequence stars and are comparable to those observed in solar active regions. If inhomogeneities are present, the surface fluxes may be markedly higher than the derived values. It is likely that the emission observed from EQ Peg was not the result of major flare activity; however, the quiescent radiative losses observed in the ultraviolet are comparable to the time-averaged optical flare losses. The similarity of the line emissions of active dwarfs of diverse spectral types suggests that the character of the transition region is independent of the stellar effective temperature.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 187
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    HEAO 1 observation of a type I burst from MXB 1728-34 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results are presented for an analysis of data on a type I X-ray burst from MXB 1728-34 observed by three large-area instruments on HEAO 1. The measurements cover the energy range from 2 to 150 keV and provide the capability of resolving significant intensity variations on a time scale of milliseconds and spectral changes on a scale of tenths of seconds. The initial rise of the burst is discussed, millisecond intensity variations are examined, and the spectral evolution of the burst is described. Physical parameters are estimated for various source models, and the total X-ray flux at energies of 85 to 180 keV during the burst is shown to have been no more than about 6% of the total observed X-ray flux at energies below 25 keV.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 188
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    Influence of a weak gravitational wave on a bound system of two point-masses (1979)
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    Publication Date: 2019-06-27
    Description: The problem of a weak gravitational wave impinging upon a nonrelativistic bound system of two point masses is considered. The geodesic equation for each mass is expanded in terms of two small parameters, v/c and dimensionless wave amplitude, in a manner similar to the post-Newtonian expansion; the geodesic equations are resolved into orbital and center-of-mass equations of motion. The effect of the wave on the orbit is determined by using Lagrange's planetary equations to calculate the time evolution of the orbital elements. The gauge properties of the solutions and, in particular, the gauge invariance of the secular effects are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 189
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    Primordial inhomogeneities in the expanding universe. II - General features of spherical models at late times (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This paper studies the density profile that forms around a spherically symmetric bound central core immersed in a homogeneous-background k = 0 or k = -1 Friedmann-Robertson-Walker cosmological model, with zero pressure. Although the density profile in the linearized regime is almost arbitrary, in the nonlinear regime certain universal features of the density profile are obtained that are independent of the details of the initial conditions. The formation of 'halos' ('holes') with densities greater than (less than) the average cosmological density is discussed. It is shown that in most regions 'halos' form, and universal values are obtained for the slope of the ln (density)-ln (radius) profile in those 'halos' at late times, independently of the shape of the initial density profile. Restrictions are derived on where it is possible for 'holes' to exist at late times and on how such 'holes' must have evolved.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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  • 190
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    Helium synthesis, neutrino flavors, and cosmological implications (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The problem of the production of helium in big bang cosmology is re-examined in the light of several recent astrophysical observations. These data, and theoretical particle physics considerations, lead to some important inconsistencies in the standard big bang model and suggest that a more complicated picture is needed. Thus, recent constraints on the number of neutrino flavors, as well as constraints on the mean density (openness) of the universe, need not be valid.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-80604
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  • 191
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    Physical characteristics of ionized gaseous nebulae (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The high angular resolution and the capability of the space telescope to observe ultraviolet radiation are discussed in relation to investigating planetary nebulae. The physical characteristics of planetary nebulae particulary the abundances of the common light elements, the H2 regions, the angular size, and the surface brightness are reviewed. Differences between supernova remants and planetary nebulae and H2 regions are discussed.
    Keywords: ASTROPHYSICS
    Type: CONTRIB-420 , NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 99-121
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  • 192
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    Interplanetary medium data book, supplement, 1975 - 1978 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Since the issurance of the Interplanetary Medium Data Book (NSSDC/WDC-A-R&S 77-04, 1977) which contains plots and listings of hourly average interplanetary field and plasma parameters covering the period November 27, 1963 through December 30, 1975, additional data are available which fill some 1975 data gaps and which extend the data coverage well into 1978. This supplement contains all the presently available data for the years 1975-1978, Interplanetary magnetic field (IMF) data are from the IMP 8 triaxial fluxgate magnetometer experiment. Derived plasma parameters are form the IMP 7 and IMP 8 instruments. Some of the early 1975 IMF data are from a HEOS 1 experiment.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-80759 , NSSDC/WDC-A-R/S-79-08-SUPPL-1
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  • 193
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    Gravitational redshift space-probe experiment (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A Scout D rocket was launched from Wallops Island, Virginia, carrying an atomic hydrogen maser oscillator system as the payload. The frequency of signals from the oscillator was monitored on the ground at Merritt Island, Florida, by using two hydrogen masers as comparison oscillators. The first-order Doppler shift in the signals was eliminated by a go-return transponder link to the payload, and the resulting data, representing the relativistic shifts, were recovered and recorded. The objective was to measure directly the effect of gravitational potential on the frequency of an atomic hydrogen maser assuming it to be a 'proper' clock. A gravitational effect amounting to some 4.5 parts in 10 to the 10th power was measured with an oscillator having a stability better than 1 part in 10 to the 14th power. Therefore, to make the best possible use of the oscillator, all frequency shifts at the 2 to 5 X 10 to the -15 power level in delta f/f in the system must be accounted for. This includes all the phase variations that can cause such a shift to appear. The experiment, the data available and the manner in which they were processed, and the results are described.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-161409
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  • 194
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    The Penrose photoproduction scenario for NGC 4151: A black hole gamma-ray emission mechanism for active galactic nuclei and Seyfert galaxies (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A consistent theoretical interpretation is given for the suggestion 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. In the case of NGC 4151, the dominant process is shown to be Penrose Compton scattering in the ergosphere of a Kerr black hole, assumed to exist in the Seyfert's active galactic nucleus.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-80624
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  • 195
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    On the Physical Environment in the Galactic Nuclei (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Galactic nuclei and quasars emit radiation over the entire electromagnetic spectrum. This suggests that concurrent observations over a wide frequency range may provide useful information in determining appropriate models for the physical environment in which the radiation is produced. In conjunction with observations by the high energy spectrometer on OSO-8, four sources have been studied in this manner; the nucleus of the elliptical galaxy, Centaurus A (NGG 5128); the quasar, 30273; the Seyfert galaxy, NGC 4151 and the nucleus of the Milky Way (GCX). Concurrent observations are used to construct the composite spectra (from radio to X-ray) for Cen A and NGC 4151 while the composite spectra of 30273 and GCX are derived from the OSO-8 data and from other observers. A skymap technique used to analyze observations of the galactic center region yielded data consistent with a significant, hard X-ray source at the radio and infrared position of the nucleus of the Milky Way. A theoretical analysis of the temporal variability of the Cen A data is undertaken and its implications discussed. Similarities between the composite spectra of the observed sources suggest that radio-bright and radio-quiet quasars may represent the emission from galactic nuclei with elliptical and Seyfert-like morphologies, respectively.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-80569
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  • 196
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    A non-LTE treatment of beryllium lines - Misidentification of the solar Be I feature at 2650 A (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The formation of beryllium lines, with particular reference to the solar Be spectrum, is investigated in a non-LTE context with a 25-level model atom in which 15 levels are allowed to depart from LTE. In some transitions, particularly the Be I 2650-A line, the non-LTE effects can be quite dramatic, changing the deduced abundances by a factor of 4. Based on the non-LTE calculations and Copernicus observations of other stars, it is found that a solar spectral feature at 2650 A, previously identified by numerous investigators as a Be I line, cannot be produced by Be I. Non-LTE effects on the Be II 3131-A line, used for most Be abundance determinations in the literature, are small by comparison.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 84; Nov. 197
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  • 197
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    High time resolution spectrophotometry of nova DQ Herculis /1934/ (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Thirty-four spectra of DQ Her are analyzed which were obtained with a time resolution greater than 0.01 cycle. It is found that: (1) the 18th mag visual companion of DQ Her has an energy distribution similar to that of a late F star and is not likely to be a member of the system; (2) the time of minimum has no wavelength dependence and agrees better with the elements of Patterson et al. (1978) than with a linear ephemeris; (3) only very weak evidence exists for the detection of a late-type star, which is of spectral type M4 or later, even at mideclipse; (4) the spectrum of the residual light at mideclipse can be represented by optically thin free-free plus bound-free emission at a temperature of 35,000 K, an electron density of (1-10) trillion per cu cm, and a star contributing about 90% of the red flux; and (5) there is a definite asymmetry in the light curve, as well as strong evidence for a localized bright spot on the side of the disk eclipsed last.
    Keywords: ASTROPHYSICS
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  • 198
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    VLA observations of stellar planetary nebulae (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Coordinates, dimensions, 4885-MHz flux densities, and brightness temperatures of K3-2, NGC 6833, Ps 1, II 5117, Me 2-2, Hb 12, Vy 1-1, and M1-5 are reported. In two other cases, H3-29 and H3-75, confused extended structure was detected in which the nebula could not be identified with certainty. He 2-467, M1-2, and Peterson's H-alpha object in M15 were also included in the observations but not detected with an upper limit of less than 10 mJy. The observations are compared with some of the previous optical and radio data, such as log S(H-beta). Distances are computed from the present data with standard assumptions. Corresponding linear radii range below 0.1 pc, among the smallest in previous distributions of radius.
    Keywords: ASTROPHYSICS
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  • 199
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    Disequilibrium condensation environments in space - A frontier in thermodynamics (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The thermal-disequilibrium aspect of the problem of dust-particle formation from a gas phase in an open space environment is discussed in an effort to draw attention to the space condensation environment as an interesting arena for application and extension of the ideas and formalisms of nonequilibrium thermodynamics. It is shown that quasi-steady states with a disequilibrium between the gas-phase kinetic temperature and the condensed-phase internal temperature appear to be the norm of condensation environments in space. Consideration of the case of condensation onto a bulk condensed phase indicates that these quasi-steady states may constitute Prigogine dissipative structures. It is suggested that a proper study of the process of condensation in a space environment should include any effects arising from thermal disequilibrium.
    Keywords: ASTROPHYSICS
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  • 200
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    Effect of hard X-rays on the emission lines of Seyfert galaxies and QSOs (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Models of photoionized emission-line regions show that inclusion of a hard X-ray component in the ionizing continuum has relatively minor effects on most optical line intensities but helps to explain the strong O VI emission observed from QSOs. The optical-forbidden lines of NGC 4151 indicate roughly solar abundances ratios of N/O/Ne/Fe. The X-ray absorption arises largely in neutral portions of the emission-line clouds.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 79; 1-2,; Oct. 197
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