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  • ASTROPHYSICS  (709)
  • 2000-2004
  • 1985-1989  (709)
  • 1955-1959
  • 1985  (709)
  • 1952
  • 101
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    Bipolar Ejection of Matter from Hot Stars (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: A general program on the internal velocities in H II regions was carried out within the past decade by the use of photographic Fabry-Perot interferometry, in the H (alpha) line and lately also in the N IIlambda 6584 line. Among the score of objects studied three H II regions and one planetary nebula possess pronounced symmetry around their ionizing stars. Velocity data combined with morphological properties suggest strongly that the nebulae were formed essentially by matter ejected from the central star and that ejection occurred preferentially from diametrially opposite regions on the star, that is, in a bi-polar fashion. The nebulae are discussed individually and a model for the ejection mechanism is presented.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 91-100
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  • 102
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    Ultraviolet Spectral Morphology of O-type Stellar Winds (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The highly systematic behavior of the stellar wind features among the majority of O-type spectra, and their strong correlations with the well-calibrated optical spectral types, are consistent with those wind models which incorporate a structural dependence on the fundamental stellar parameters. On the contrary, wind models which postulate a predominance of random rotational or magnetic effects, unrelated to the fundamental stellar parameters, are not supported by the ultraviolet spectral morphology; rather, such effects may contribute to the observed properties of some of the exceptionally peculiar objects.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 66-69
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  • 103
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    New Instabilities in Line Driven Winds (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The physical mechanisms which potentially lead to instabilities in line driven winds, the drift instability and the line shape instability, are discussed. A general three dimensional treatment of the stability problem of line driven winds which leads to the general dispersion equation is proposed. From this dispersion equation automatically a third physical mechanism driving instability in stellar winds is deduced; the thermal drift instability which is related to changes in absorption of radiation caused by temperature perturbations. This mechanism results in growing inwardly propagating sound waves.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 226-232
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  • 104
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    Magnetic Effects in the Heating and Modification of Flows in the Outer Stellar Atmospheres with Application to Early Type Star Case (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Possible magnetic effects in the heating and modification of flows in early type star atmospheres are discussed by referring to the physically related phenomena dealt with for late type stars, young stars, and close binary systems. It is pointed out as the result of that the magnetic field may play important roles also in early type star atmospheres in converting the energy of the radiatively driven outflow into heat, or in modifying the outflow by nozzling or by initial modification of temperature and/or momentum by which the effect of the radiation pressure may be made the most of in accelerating the outflow.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 199-220
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  • 105
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    Effect of Scattering on Instabilities in Line-driven Stellar Winds (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Line driven O-B stellar winds are unstable to perturbations of short spatial wavelength and the growth rates for such instabilities are very rapid. The nature of the nonlinear development of this instability is unknown, but might possibly be one of blobs of gas driven through ambient gas or a quasiregular train of outward moving shocks. In either case the resulting dissipation of mechanical energy might explain the observed anomalous heating n O-B stars as evidenced by their X-ray emission and high ionization state. It also might explain the observed fine structure of the absorption lines and their time variability. The driving due to the absorption of the stellar continuum flux was considered and the effects of the diffuse, scattered radiation field were neglected. It was shown that under certain special conditions the effect of scattering could reduce the instability growth rate to zero. A stability analysis that includes scattering, but that uses the more physically realistic assumption of complete redistribution instead of coherent scattering, and that includes the effects of transverse velocity gradients, which become important as the flow moves away from the stellar surface is presented. It is found that the instability is eliminated right at the base of the wind, but that as the flow moves outward the instability rate rapidly becomes equal to a substantial fraction of the calculated value, the fraction asymptotically reaching 80% at large radii. Since this still implies many e folds in a characteristic outflow time, the primary conclusion that these winds are highly unstable is unchanged.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 221-225
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  • 106
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    Summary of the Origin of Nonradiative Heating/momentum in Hot Stars (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Nonradiative heating in the atmospheres of stars and the deposit of nonradiative momentum in the stellar atmosphere were examined. Observations made from space have been very important in changing the concept of what a star is like. In order to interpret the spectroscopic information gained in the wavelength region inaccessible from the surface of the Earth, chiefly in the domain of X-rays and of ultraviolet radiation. The assumptions which underlie the theory of stellar atmospheres will have to be reused. Improved observation facilities are major reasons to consider new ideas for interpreting the spectra of stars. The photometric precision and sensitivity for observing at high and at moderate spectral resolutions have increased greatly. The development of high dispersion, high resolution spectrographs for observing is noted.
    Keywords: ASTROPHYSICS
    Type: The Origin of Nonradiative Heating(Momentum in Hot Stars; p 243-254
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  • 107
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    Radiative Amplification of Acoustic Waves in Hot Stars (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The discovery of broad P Cygni profiles in early type stars and the detection of X-rays emitted from the envelopes of these stars made it clear, that a considerable amount of mechanical energy has to be present in massive stars. An attack on the problem, which has proven successful when applied to late type stars is proposed. It is possible that acoustic waves form out of random fluctuations, amplify by absorbing momentum from stellar radiation field, steepen into shock waves and dissipate. A stellar atmosphere was constructed, and sinusoidal small amplitude perturbations of specified Mach number and period at the inner boundary was introduced. The partial differential equations of hydrodynamics and the equations of radiation transfer for grey matter were solved numerically. The equation of motion was augmented by a term which describes the absorption of momentum from the radiation field in the continuum and in lines, including the Doppler effect and allows for the treatment of a large number of lines in the radiative acceleration term.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 233-235
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  • 108
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    A Leaky Waveguide Model for MHD Wave Driven Winds from Coronal Holes (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: Magnetohydrodynamic (MHD) waves, driven by the large scale convective motions of the photosphere are suggested as a possible source of additional acceleration for the stellar wind. Most of the turbulent power in a coronal hole is carried by MHD waves with periods of a few hundred seconds or longer. This is evident from direct observations of turbulence in the solar photosphere, as well as in situ observations of turbulence in the solar wind. But waves with periods this long have wavelengths which are typically as large as the transverse scale of the coronal hole flux tube itself. For these waves boundary effects are important and the coronal hole must be treated as a waveguide. The propagation of MHD waves using this waveguide approach is discussed. The simple model presented demonstrates that coronal holes can act as waveguides for MHD waves. For typical solar parameters the waves are compressible and can generate a wave tensile force which tends to cancel at least part of the wave pressure force. This effect tends to decrease the efficiency of MHD wave acceleration.
    Keywords: ASTROPHYSICS
    Type: The Origin of Nonradiative Heating(Momentum in Hot Stars; p 183-187
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  • 109
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    Non-radiative Energy from Differential Rotation in Hot Stars (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: A model of differential rotation is proposed for the upper radiative envelopes of hot stars, and it is suggested that the actions of such motions can be the source of energy for heating the coronae.
    Keywords: ASTROPHYSICS
    Type: The Origin of Nonradiative Heating(Momentum in Hot Stars; p 164-168
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  • 110
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    Is the Ratio of Observed X-ray Luminosity to Bolometric Luminosity in Early-type Stars Really a Constant? (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The observed X-ray emission from early-type stars can be explained by the recombination stellar wind model (or base coronal model). The model predicts that the true X-ray luminosity from the base coronal zone can be 10 to 1000 times greater than the observed X-ray luminosity. From the models, scaling laws were found for the true and observed X-ray luminosities. These scaling laws predict that the ratio of the observed X-ray luminosity to the bolometric luminosity is functionally dependent on several stellar parameters. When applied to several other O and B stars, it is found that the values of the predicted ratio agree very well with the observed values.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 159-163
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  • 111
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    Laboratory and astronomical identification of cyclopropenylidene, C3H2 (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Twenty-seven rotational lines of C3H2 have been identified in the laboratory or in astronomical sources, and the rotational and centrifugal distortion constants of this previously unobserved carbene ring determined to high accuracy. The assigned astronomical transitions include the strong, ubiquitous interstellar lines at 85,338 MHz and 18,343 MHz, which are the lowest lying transitions of ortho C3H2:2(12) to 1(01) and 1(10) to 1(01), respectively. Interstellar C3H2 can be rapidly formed by dissociative recombination of the very stable ion C3H3(+), which in turn can be produced from acetylene in only two stars. In standard molecular sources such as Ori A and Sgr B2, C3H2 is only moderately abundant, but in diffuse molecular clouds it may be one of the most abundant molecules. There is some radio spectroscopic evidence for two related molecules in Sgr B2 or TMC-1: ethynylmethylene HCCCH, a hypothetical carbon chain isomer, and cyclopropene, C3H4, a known, stable three-membered ring.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 299; L63-L66
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  • 112
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    Source counts at 5 gigahertz from the MG survey (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The MIT-Green Bank (MG) radio survey (reported by Bennett and colleagues in 1984 and 1985) is the largest 5 GHz survey to date. In this paper the source counts from the MG survey are examined. They are consistent with past measurements, but due to the large size of the MG survey the Poisson errors have been reduced. Radio source evolution models (such as that reported by Condon in 1984) are consistent with these new measurements.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 299; 373
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  • 113
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    Soft X-rays, winds, and the cataclysmic variable boundary-layer problem (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Models are presented for the effects of a stellar wind on the UV and soft X-ray spectra of cataclysmic variables (CVs). It is shown that P Cygni absorption lines observed from many CVs are consistent with the existence of a strong wind, and that such a wind can also account for the soft X-ray upper limits if the wind mass loss rate is about 10 to the -8th solar masses per yr. The implications of such a wind for the CV momentum and energy budget are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 299; 277-285
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  • 114
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    Emission features in the 4-13 micron spectra of the reflection nebulae NGC 7023 and NGC 2023 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Spectroscopy from 4 to 13 microns of the visual reflection nebulae NGC 7023 and NGC 2023 has been obtained. These data, together with previous work from 1 to 4 microns, show that the spectra of these sources consist of a relatively flat continuum from 1 to 13 microns and six emission features at 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 microns. The observations rule out equilibrium thermal emission for the features and continuum in reflection nebulae, and point toward a nonequilibrium emission mechanism such as thermal emission from thermally fluctuating small grains or fluorescence from large molecules. The similarity of the emission feature spectra in reflection nebulae to those in other sources suggests a universal emission mechanism, thus implying nonequilibrium emission mechanisms in other sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 299; 416-423
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  • 115
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    Temperatures within comet nuclei (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Knowledge of the temperature distribution within comet nuclei is critical to the understanding of the state and behavior of comets. The present study is concerned with the temperature profile below the surface of the nucleus and below any dust mantle which may be present. With respect to the physics, the considered model is in some respects similar to that discussed by Weissman and Kiefer (1981, 1984). However, the new model is improved in various respects. It represents the first attempt to investigate directly the detailed nature of thermal profiles within a comet nucleus. Included in the investigation are calculations which consider the effects of variations in latitude, nucleus spin axis orientation, surface albedo, and thermal emissivity. It is shown that the application of the model, together with in situ measurements of temperatures within a cometary nucleus, could significantly constrain the range of possible subsurface physical properties.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 12
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  • 116
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    Optical region elemental abundance analyses of B and A stars. IV - Re-evaluation with new critically compiled Fe II oscillator strengths and improved estimates of the damping constants (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new critical compilation of Fe II f-values has recently been completed by Martin et al. To see how these values affect the derived stellar abundances both directly in changing the values of log Fe/H for individual lines and through the determination of the microturbulent velocities, the data for 11 (six normal and five slightly peculiar) sharp-lined B and A stars have been reanalyzed. At the same time, the choice of line damping constants has been investigated, especially for Fe I and Fe II lines.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 152; 2, No
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  • 117
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    On the ultraviolet energy distributions and the temperatures of peculiar B and A stars (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Color temperatures have been estimated by comparing ultraviolet observations of HgMn and magnetic Ap stars with those of normal stars. Ultraviolet data from the OAO-2, ANS, TD-1, and IUE satellites generally give similar results. The values for the normal stars were derived from comparison of fluxes predicted by solar-composition fully line-blanketed model atmospheres with optical region spectrophotometry. The ultraviolet temperatures of the HgMn stars cover a narrower temperature range than do their optical region values. Magnetic Ap stars with similar optical region temperatures can show substantial differences in their ultraviolet color temperatures. This may result from magnetic field configuration and abundance differences.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 97; 970-975
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  • 118
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    Spatially extended 10 micron emission from the infrared reflection nebula GSS30 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A surface brightness map and point-wise photometry at 10 microns of the infrared reflection nebula GSS30 were made with the Wyoming 2.3-m telescope. Extended emission is detected as far as 10 arcsec north of the illuminating star, IRS1. The photometry shows that the nebular surface brightness is a factor of three more than that expected from thermal emission from dust grains. If the 10 micron flux is due to scattering, then grains with a radius of 1.6 microns are required. Alternatively, the 10 micron flux is consistent with the flux expected from the unidentified IR emission features at 7.7, 8.6, and 11.3 microns.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 97; 924-929
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  • 119
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    Outer solar system materials - Ices and color systematics (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Our program of VJHK colorimetric observations and spectrophotometry is reviewed and updated. Attention is given to the probable connections between VJHK colors and the ratios of bright ices and dark soils on many outer solar system small bodies' surfaces. VJHK color systematics may clarify ice/soil behaviors in bodies too faint for high resolution spectra. Comets appear colored by soils most closely resembling D-class Trojan asteroid soils. Our recent model of comet surface properties, involving weakly-bonded ice/soil regoliths, helps explain comet eruptive phenomena. The work suggests the importance of considering ices in the context of their intimate mixture with non-volatile soils.
    Keywords: ASTROPHYSICS
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  • 120
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    High-dispersion ultraviolet spectra of the peculiar star RX Puppis (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High spectral resolution observations of the peculiar star RX Puppis obtained with the International Ultraviolet Explorer suggest the presence of a complex gaseous ring system which surrounds an accreting hot secondary. The anomalous line intensity ratio of the C IV 1548, 1550 A doublet during the observations exceeded the optically thick limit, implying the presence of a high-velocity wind. Additionally, the C IV doublet exhibits about four or five narrow emission components, which are redshifted up to velocities of at least about + 300 km/s (with respect to the rest wavelength).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 59; 785-798
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  • 121
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    Time dependent chemistry in dense molecular clouds. I - Grain surface reactions, gas/grain interactions and infrared spectroscopy (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: For the fist time, a time-dependent model is described which includes the role of grains in the production of molecules in dense clouds including ion-molecule gas phase chemistry. The approach provides information regarding the coupling between the two phases. Although the coupling between the two chemistries is extremely strong, the two domains maintain their own identities. While H2O, CH4, and NH3 are made efficiently, with a high production rate on grains and released back to the gas phase, the gas phase is essentially responsible for the formation of CO, a very stable molecule which may or may not react on grains with atomic oxygen and may or may not form CO2.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 152; 1, No
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  • 122
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    CO emission structure in the Taurus molecular cloud complex (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A survey is reported of the J = 1 - 0 2.6-mm transition of CO, covering 11.5 square degrees toward the Taurus dark cloud complex, including Heiles Cloud 2 and DL 2. The main finding is the presence of systematic velocity structure in the Barnard 18 region of DL 2. This structure is tentatively interpreted as an expanding shell of molecular gas of diameter about 3 pc centered on a cluster of young T Tauri stars. The estimated momentum of the shell is consistent with that expected from winds from the young stars seen in the shell.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 298; 818-826
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  • 123
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    Visibility of Halley's nucleus from the Giotto spacecraft (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An effort is made to estimate the visibility of the patterns on the nucleus of Comet Halley from the Giotto spacecraft through the comet's dusty coma. The visibility computation is based on the theory of contrast reduction by a scattering and absorbing medium (a planetary atmosphere). It is shown that some details may be seen on the surface of the cometary nucleus even for an optical thickness as high as 2. It is noted that the surprisingly large apparent contrast for such large optical thicknesses can be explained by the strong forward scattering by the dust.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 64; 20-26
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  • 124
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    Evidence for supermassive stars in three Seyfert galaxy nuclei from IUE spectra (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The variability in the ultraviolet continua and the C IV 1550 A emission profiles in the three Seyfert 1 galaxies NGC 4151, NGC 5548, and Fairall 9 are consistent with origin in supermassive stars undergoing explosive mass loss. Blackbody fits to continua of each imply a single thermal source whose area either remains constant or increases moderately as its temperature decreases, with the surface area consistent with stars having masses from 10 to the 6th to 10 to the 8th solar mass. Line emission profiles of C IV 1550 A in the same spectra are individually consistent with uniform expansion of shells of emitting gas expelled from the stars at radial velocities from 10,000 to 16,000 km/s. The kinetic energy removed by repetitive production of such massive shells approximately balances the nuclear energy production expected from supermassive stars of the indicated size. Finally, the observed nature and time scale of the variability of NGC 4151 is consistent with the relatively sudden appearance, and subsequent cooling, of the underlying superstellar surface as one such shell becomes transparent during its expansion.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 611-620
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  • 125
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    Protostellar disks and star formation (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The status of theoretical work on protostellar disks is reviewed. Accretion disk theory and its application to models of the solar nebula and protostellar disks are discussed. A unified view of the process of star formation is presented, starting from the evolution of molecular clouds, and leading naturally to the formation of protostellar disks. The models used to describe this process are idealized, but are believed to provide good prototypes that well represent the essential hydromagnetic phenomena involved in star and disk formation. Several possible evolutionary paths and final configurations are qualitatively discussed, showing how the outcomes depend on the relative efficiencies of various angular momentum transport processes.
    Keywords: ASTROPHYSICS
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  • 126
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    Short-lived nuclei in the early solar system (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An overview is given of the existence and abundance of short-lived nuclei that were present in the early solar system. It is shown that there are excesses of certain isotopes that may be assigned to the decay of short-lived radioactive nuclei corresponding to an abundance of about 0.0001 relative to a neighboring stable isotope. This abundance is roughly similar to the level of general nonlinear isotopic anomalies present in meteoritic material (excluding oxygen) which are not attributable to short-lived nuclei. If these results are representative of the bulk solar system, they indicate that about 0.0001 solar mass of freshly synthesized material of peculiar composition was added to the protosolar nebula as it was formed from the interstellar medium. This material must have been synthesized about three million yr before the formation of the solar system.
    Keywords: ASTROPHYSICS
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  • 127
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    The chemical state of dense interstellar clouds - An overview (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The currently known interstellar molecules and isotopes are listed, procedures for determining relative chemical abundances in molecular clouds are discussed, and current best estimates for such abundances in regions of differing physical properties are presented. Among the results are a general chemical similarity across a range of density and temperature for quiescent clouds, and some striking differences among regions which are not easily related to such physical parameters and may instead reflect cloud history and evolution. The possibility of constraining chemical models via measurements of relative abundances for the isomeric pairs HNC/HCN, CH3NC/CH3CN, and HOC(+)/HCO(+) is discussed in detail.
    Keywords: ASTROPHYSICS
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  • 128
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    Protostars and planets - Overview from a planetary perspective (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Today the simultaneous formation of a star and planetary system is understood to be natural and coupled consequences of the collapse of an interstellar cloud of molecular gas and dust. Ideas put forward to account for the existence of the solar system seem generally applicable to star formation throughout the universe. If this is indeed the case, then planetary systems should be present in large numbers throughout the universe. Even the gross structural features of the planetary system in the solar system seem largely to be the result of nearly deterministic processes, rather than the result of chance alone; many planetary systems throughout the universe may resemble this one. This chapter summarizes and examines some of the implications of ideas about the formation of stars and planetary systems.
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  • 129
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    X-ray observations of GX 1 + 4 with the monitor proportional counter on board the Einstein Observatory (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The results of X-ray observations of GX 1 + 4 with the monitor proportional counter on board the Einstein Observatory (HEAO 2) are presented. Using data from the time interval processor, the value of the approximately 2 minute pulse period at the time of the observations was determined. Previous determinations are discussed, along with evidence for a suggested value of approximately 4 minutes for the pulse period. The phase of first harmonic of the Fourier decomposition of pulse profile is stable within its errors but the phases of higher harmonics are not. The spin-up time scale is determined to be approximately 40 years.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 288-295
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    A wide-latitude CO survey of molecular clouds in the northern Milky Way (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A wide-latitude, low angular resolution survey of CO along most of the first Galactic quadrant and part of the second was undertaken in order to investigate molecular clouds associated with the Great Rift and the diffuse component of Galactic gamma rays. The main nearby clouds have masses between a few times 10,000 and a few times 100,000 solar masses, versus a few times a million solar masses for the largest complexes elsewhere. The CO emission in the survey comes nearly equally from local clouds associated with the Great Rift and from distant clouds in the inner arms of the Galaxy 4-7 kpc from the Galactic center. The half-thickness at half-intensity of the local molecular cloud layer is greater than 50 pc and is estimated to be 75 + or - 25 pc. The results strongly support the notion that all dark nebulae are molecular clouds, and vice-versa.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 751-765
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  • 131
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    Highly supersonic bipolar mass ejection from a red giant OH/IR source - OH 0739 - 14 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: From long-slit spectrophotometry of the bipolar nebula associated with the unusual OH source, OH 0739 - 14, the presence of a blue companion to the M9 III central star was shown and a Herbig-Haro-like knot beyond each nebular lobe was discovered. From differential colors of the lobes and from radial velocities of these knots it was demonstrated that the system inclines its northern lobe in the forward direction. It was also shown that the nebulous knots are shocks being driven into an extensive circumstellar envelope, and that this material is very overabundant in nitrogen, suggesting that it is matter lost from a star of mass greater than 3 solar masses. A model of biconical ejection from a central binary is consistent with the OH observations, and a possible relation of OH 0739 - 14 to the symbiotic stars and to bipolar planetary nebulae is suggested.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 702-709
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  • 132
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    The infrared echo of Type II supernovae with circumstellar dust shells. II - A probe into the presupernova evolution of the progenitor star (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper studies the spectral appearance and evolution of the infrared light curve, also referred to as the infrared echo, of Type II supernovae embedded in carbon- or oxygen-rich circumstellar dust shells. The distinct spectral signature of the echo and its temporal evolution can be used to estimate the mass of the shell and identify the composition of the dust. Since the shell mass and dust composition are determined by the combined effect of stellar mass loss and the dredging of newly synthesized heavy elements to the stellar surface, observations of the infrared echo may provide useful clues to the presupernova evolution of the progenitor star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 719-723
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  • 133
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    Time-dependent interstellar chemistry (1985)
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    Publication Date: 2011-08-19
    Description: Some current problems in interstellar chemistry are considered in the context of time-dependent calculations. The limitations of steady-state models of interstellar gas-phase chemistry are discussed, and attempts to chemically date interstellar clouds are reviewed. The importance of studying the physical and chemical properties of interstellar dust is emphasized. Finally, the results of a series of studies of collapsing clouds are described.
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  • 134
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    The nature and origin of Herbig-Haro objects (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A brief description of the nature of Herbig-Haro nebulae is given, and the shock-wave origin of the nebulae is discussed. Kinematical evidence suggests that Herbig-Haro objects are ejected in bipolar flows from young stars. Evidence from infrared observations of the stars that excite Herbig-Haro objects is summarized; these stars appear to be T Tauri stars. The origin of these nebulae is discussed emphasizing energy required to power them, and a number of questions are posed pertaining to outflow mechanisms associated with the exciting stars.
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  • 135
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    Young stellar objects and their circumstellar dust - An overview (1985)
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    Publication Date: 2011-08-19
    Description: The basic observational classes of young stellar objects are briefly reviewed and some of the theoretical and observational problems in premain sequence stellar evolution are discussed. The evidence which indicates that the infrared excesses in recently formed stars are primarily due to thermal emission from circumstellar dust is summarized. Various indirect lines of evidence on the spatial distribution of the circumstellar dust are examined, and it is concluded that the concentration of the dust in a large disk structure is the most viable model at this time.
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  • 136
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    Semiclassical instability of compactification (1985)
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    Publication Date: 2011-08-19
    Description: It is shown that several schemes for compactification of the extra dimensions in Kaluza-Klein theories are unstable to a quantum gravitational process of barrier penetration: The universe can tunnel from a state with static extra dimensions to a de Sitter expansion of all dimensions. The tunneling rate is estimated, and it is found that the present state of the universe is probably long-lived (in good agreement with observation).
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 55; 1435-143
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  • 137
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    The origin of comets - Implications for planetary formation (1985)
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    Publication Date: 2011-08-19
    Description: Primordial and episodic theories for the origin of comets are discussed. The implications of the former type for the origin of the solar system are considered. Candidate sites for the formation of comets are compared. The possible existence of a massive inner Oort cloud is discussed.
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  • 138
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    Star formation - An overview (1985)
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    Publication Date: 2011-08-19
    Description: Methods for studying star formation are reviewed. Stellar clusters and associations, as well as field stars, provide a fossil record of the star formation process. Regions of current star formation provide a series of snapshots of different epochs of star formation. A simplified picture of individual star formation as it was envisioned in the late 1970s is contrasted with the results of recent observations, in particular the outflow phenomenon.
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  • 139
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    Laboratory and astronomical detection of the deuterated ethynyl radical CCD (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Two rotational transitions of CCD, N = 1-2 at 144 GHz and 2-3 at 216 GHz, were detected in a laboratory glow discharge through deuterated acetylene and helium, after which one, N = 2-1, was detected toward the rich molecular cloud behind the Orion Nebula. The 144 GHz transition is a well-resolved spin doublet split by 55 MHz, the components of which contain hyperfine structure of the order of 1 MHz, so far only partially resolved. From observations toward two positions in Orion, at and near the Kleinmann-Low nebula, the column density of CCD is determined to be 1.8 x 10 to the 13th/sq cm and the isotopic ratio CCD/CCH = 0.05. CCD was not detected at two positions in TMC-1.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 296; L35-L38
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  • 140
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    A precise measurement of the cosmic microwave background temperature from optical observations of interstellar CN (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Very precise observations (with S/N greater than 2000) of the 3874-angstrom band of interstellar CN toward zeta Per and omicron Per are presented. In the zeta Oph, zeta Per, and omicron Per lines of sight, the saturation-corrected CN line strengths yield respective excitation temperatures of 2.72 plus or minus 0.05 K, 2.76 plus or minus 0.05 K, and 2.78 plus or minus 0.07 K for the J = 0-1 rotational transition at 2.64 mm. By confirming the blackbody character of the cosmic microwave background spectrum at wavelengths near the peak of its flux, the simplest explanation of the background as primeval fireball radiation from a hot bang is reinforced.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 119-132
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  • 141
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    Narrow-band forbidden O III imaging of the QSO 4C 18.68 - A tidal tail revealed? (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The z = 0.313 quasar 4C 18.68 and its surroundings in the light of redshifted forbidden O III were imaged. The QSO appears much more extended than in broad-band images, with a large halo and possibly a faint tidal tail discerned. A broad-band I CCD image taken in 1 - 1.2 arcsec seeing resolves the QSO from a companion galaxy 3.6 arcsec distant, similar to many others seen in the field. It is suggested that the elongated and asymmetric shapes of some QSOs may be due to not-quite-resolved companion galaxies, and that caution be exercised in interpreting luminosity and color profiles as evidence for underlying spiral or elliptical structure.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 296; 399-401
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  • 142
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    Cometary dynamics (1985)
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    Publication Date: 2011-08-19
    Description: Modern theories of cometary dynamics are described. Attention is given to Oort's hypothesis that the Solar System is surrounded by a spherically symmetrical cloud of about 10 to the 11th to 10 to the 12th comets extending out to interstellar distances. Dynamical modelling and statistical analyses of cometary motion have confirmed the ability of the Oort hypothesis to explain the observed distribution of energies for the long-period cometary orbits. Some of the sources cometary motion perturbations are discussed, including: random passing stars; interstellar clouds; and the galactic gravitational field. Perturbations in cometary motion in the planetary region are attributed to the gravitational fields of the major planets and nongravitational forces resulting from jetting of volatiles on the surfaces of cometary nuclei. Observational evidence for the existence of a massive inner Oort cloud extending from just beyond the orbit of Neptune to 10,000 AU is presented.
    Keywords: ASTROPHYSICS
    Type: Space Science Reviews (ISSN 0038-6308); 41; 299-349
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  • 143
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    Is the Kolmogoroff model applicable to large-scale turbulence? (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In view of the present discussion, the Heisenberg-Kolmogoroff (HK) model of turbulence that is often used for turbulent phenomena on all scales is actually valid for a turbulent spectrum wavelength band typically much smaller than the size of the system, and cannot describe phenomena at large scales in astrophysical systems. The results of mixing length theory cannot be accommodated within the HK model's framework without the adoption of an unreasonable coupling constant. It is also noted that the use of the observed velocity-size relationship in molecular clouds with turbulent velocity values of about l to the 1/2-power, within the HK model, gives rise to a growth rate that does not correspond to any known physical processes suspected of operating in molecular clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 116; 2, No; 367-375
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  • 144
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    He2-36 - A planetary nebula with a high velocity jet? (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The ultraviolet spectrum of the planetary nebula He2-36 was observed in the low-dispersion mode of the IUE. Strong emission lines of semiforbidden C III, He II, and C IV are observed, as well as some weak line and a moderately strong stellar continuum, suggesting a hot companion to the visual A2 III central star. The extinction to He2-36 was determined from the He II I (1640)/I (4686) ratio. The C IV line has an unusual split structure. If the 1545 component is due to a blueshifted component from the 'jet' emanating from the nebula, its velocity would be -600 km/s, which is unique for a planetary nebula.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 2550-255
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  • 145
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    High-spatial-resolution studies of young stellar objects. II - A thick disk surrounding Lynds 1551, IRS 5 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Heavily oversampled, small (2 arcsec) beam 2 micron maps of the region surrounding Lynds 1551, IRS 5 provide the basis for reconstructing maximum-entropy 'images' which have an effective spatial resolution of about 0.6 arcsec. These images reveal an extended, cusp-like structure surrounding IRS 5. This structure most likely results as light from IRS 5 is scattered in our direction by dust grains located in a thick disk of diameter 1000 AU. The disk is viewed nearly edge-on and has a mass in dust grains of 2 to 5 x 10 to the -5th solar masses. Its polar axis lies along the observed direction of the bipolar mass outflow inferred from molecular line observations of the L1551 cloud. It is possible that the observed infrared disk may represent the inner regions of a much larger thick-disk structure, whose shape derives from the combined effects of disk rotation and the gravitational field of IRS 5.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 2575-258
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  • 146
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    Images in the rocket ultraviolet - The stellar population in the central bulge of M31 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Imagery of the bulge of M31 obtained with a rocket-borne telescope in two broad bands centered at 1460 A and 2380 A is discussed. The UV spatial profiles over a region about 200 arcsec wide are identical with those at visible wavelengths. The absence of detectable point sources indicates that main-sequence stars hotter than B0 V are not present in the bulge. It is suggested that the far-UV flux in old stellar populations originates in post-AGB stars. The UV flux from such stars is extremely sensitive to age and the physics of their previous mass loss.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 298; L37-L40
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  • 147
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    Evolution of massive stars in very young clusters and associations (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Statistics concerning the stellar content of young galactic clusters and associations which show well defined main sequence turnups have been analyzed in order to derive information about stellar evolution in high-mass galaxies. The analytical approach is semiempirical and uses natural spectroscopic groups of stars on the H-R diagram together with the stars' apparent magnitudes. The new approach does not depend on absolute luminosities and requires only the most basic elements of stellar evolution theory. The following conclusions are offered on the basis of the statistical analysis: (1) O-tupe main-sequence stars evolve to a spectral type of B1 during core hydrogen burning; (2) most O-type blue stragglers are newly formed massive stars burning core hydrogen; (3) supergiants lying redward of the main-sequence turnup are burning core helium; and most Wolf-Rayet stars are burning core helium and originally had masses greater than 30-40 solar mass. The statistics of the natural spectroscopic stars in young galactic clusters and associations are given in a table.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 298; 521-527
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  • 148
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    Collisional excitation of molecules in dense interstellar clouds (1985)
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    Publication Date: 2011-08-19
    Description: State transitions which permit the identification of the molecular species in dense interstellar clouds are reviewed, along with the techniques used to calculate the transition energies, the database on known molecular transitions and the accuracy of the values. The transition energies cannot be measured directly and therefore must be modeled analytically. Scattering theory is used to determine the intermolecular forces on the basis of quantum mechanics. The nuclear motions can also be modeled with classical mechanics. Sample rate constants are provided for molecular systems known to inhabit dense interstellar clouds. The values serve as a database for interpreting microwave and RF astrophysical data on the transitions undergone by interstellar molecules.
    Keywords: ASTROPHYSICS
    Type: Nuovo Cimento C, Serie 1 (ISSN 0390-5551); 8; 435-449
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  • 149
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    An X-ray, optical and radio study of PKS 0745-191 - A massive cooling flow (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The X-ray source 3A 0745-191 is identified with intracluster gas surrounding the giant galaxy containing the radio source, PKS 0745-191, which lies at z = 0.1. The gas is cooling at the unprecedented rate of 1000 solar mass/yr. Optical line-emitting gas extends more than 10 kpc from the centre of the galaxy and corroborates the high mass-flow rate. The optical spectrum is similar to that of distant 3CR radio galaxies reported by others. It is concluded that formation of a giant galaxy was observed.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 216; 923-932
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  • 150
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    Spectrophotometry of peculiar B and A stars. XVIII - The helium rich variable stars HR 1890, Sigma Orionis E, and HD 37776 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Optical region spectrophotometry at 3300-7850 A has been obtained for three helium rich stars, HR 1890, Sigma Ori E, and HD 37776, of the Orion OB1 Association. New uvby-beta photometry of HR 1890 and HD 37776 as well as published data are also used to investigate the variability of these stars. A new period of 1.53862 days was determined for HD 37776. For all three stars H-beta varies in antiphase with strong He I lines. The spectrophotometric bandpass containing the strong He I line at 4471 A varies in phase with the R index of Pedersen and Thomsen (1977). Evidence is found for weak absorption features which appear to be an extension of the 5200 A feature seen in cooler CP stars.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 62; 279-290
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  • 151
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    Probing the local interstellar medium (1985)
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    Publication Date: 2011-08-19
    Description: A sophisticated model of solar wind expansion is applied to deduce a range of parameters for the local interstellar medium that predicts a location for the heliospheric shock of about 30 AU. It is found that either the interstellar magnetic field is more than double the presently accepted value of 0.3 nT, or the pressure due to galactic cosmic rays with energies near 0.1 MeV is that obtained by simple extrapolation of the observed flux at higher energies inside the heliosphere. Alternatively, some combination of these two external effects yields an effective interstellar pressure approximately quadruple present estimates.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 317; 702
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  • 152
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    Thermal infrared and nonthermal radio - Remarkable correlation in disks of galaxies (1985)
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    Publication Date: 2011-08-19
    Description: A tight, linear correlation is established between the far-infrared flux measured by IRAS and the nonthermal radio flux density (at 1.4 GHz) from disks of spiral galaxies. This correlation defines a ratio of infrared to radio fluxes that is characteristic of star formation activity. Galaxies with nuclear starbursts seem to follow the correlation. If the far-infrared is reradiated luminosity from young massive stars, then the supernova remnants alone account for less than 10 percent of the radio emission. These results indicate a close coupling between dust heating and cosmic-ray generation and confinement in a wide range of conditions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 298; L7-L11
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  • 153
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    An optical and infrared study of the region surrounding Herbig-Haro objects 1 and 2 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Optical and near-IR observations of the environs of H-H objects 1 and 2 provide the basis for identifying a recently discovered radio continuum as the star responsible for powering the highly collimated mass outflow traced by these objects. Polarimetric observations show that the source (designated as VLA 1), located at the midpoint between HH 1 and 2, illuminates a biconical reflection nebula. It is suggested that VLA 1 is probably surrounded by an optically thick disk viewed edge on; an optical 'jet' emanates from the vicinity of HH 1 and is directed along the axis of the putative disk toward HH 1; its spectrum resembles that of HH 1 and other Herbig-Haro objects.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 2281-229
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  • 154
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    Stellar activity cycles (1985)
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    Publication Date: 2011-08-19
    Description: The variety of stellar chromospheric and coronal activity provides a framework for understanding solar and stellar magnetic activity. It is pointed out that the recognition of an 11-yr periodicity within the record of sunspot numbers is a relatively recent discovery of just over a century ago. The solar activity cycle is examined, taking into account the sunspot cycle, and solar dynamo models. Time-averaged stellar chromospheric activity levels are considered along with long-term activity fluctuations of cool stars. Attention is given to the direct measurement of stellar magnetic fields, solar luminosity variations, the RS Canum Venaticorum and BY Draconis variables, continuum variations in lower main sequence stars, chromospheric variations in lower main sequence stars, and chromospheric variations in evolved stars.
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  • 155
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    Comments on techniques for spectral deconvolution (1985)
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    Publication Date: 2011-08-19
    Description: Current observational questions in asteroseismology require high spectral resolution that can be only be obtained with observations spanning many days or months. The primary constraint in the full utilization of single mid-latitude observing sites is the presence of diurnal data gaps. Several methods for removing the effect of these gaps in the spectral obtained from velocity observations have been suggested. In the case of data coverage of less than 50%, none of the methods considered has been successful at unambiguously recovering the true spectrum from test spectra with realistic complexity. The limitations of these methods and their applicability to the helioseismology problem is discussed.
    Keywords: ASTROPHYSICS
    Type: Contributions to Proceedings from the NATO Advanced Research Workshop on the Seismology of the Sun and the Distant Stars; p 19-22
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  • 156
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    Milliarcsecond structures, VLBI and optical positions of 8 HIPPARCOS radio stars (1985)
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    Publication Date: 2011-08-19
    Description: Mark 3 VLBI observations show evidence for complex radio structures on the milliarcsecond angular scale of 8 HIPPARCOS radio stars. Their VLBI positions and optical positions measured with the automatic meridian circle in Bordeaux are presented. Comparison between the optical and VLBI positions of these stars shows that the JPL VLBI reference frame and the FK4 fundamental catalog are aligned at the level of precision of the optical measurements (O".05).
    Keywords: ASTROPHYSICS
    Type: ESA The European Astrometry Satellite HIPPARCOS: Scientific Aspects of the Input Catalog Preparation; p 251-253
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  • 157
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    Improved cross section calculations for astrophysical applications (1985)
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    Publication Date: 2011-08-19
    Description: Modifications are proposed for the semiempirical equations and parameters of Silberberg and Tsao (1973) for partial cross section calculations of proton-nucleus reactions in cosmic rays. These modifications include: adjustment of general parameters; modification of energy dependence; effects of nuclear alpha-particle structure, deuteron emission, and even-charged products; peripheral reactions; fission reactions; averaging cross sections near boundaries of different parameters; elimination of certain special cases; and treatment of the Pt to Pb group that cannot yet be generalized to Z(t) less than 76.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 58; 873-881
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  • 158
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    The Sigma-D relation for shell-like supernova remnants (1985)
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    Publication Date: 2011-08-19
    Description: A large fraction of Galactic supernova remnants, including a dozen shell-like remnants, can be associated with large molecular clouds or cloud complexes with well-determined distances. The Sigma-D relation for these shell-like remnants, derived using distances to the associated molecular clouds, shows substantially smaller scatter than previous relations and establishes a good distance scale for shell-like remnants from Type II events.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 295; L13-L16
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  • 159
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    An attempt to detect mass loss from Alpha Lyrae with the VLA (1985)
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    Details
    Publication Date: 2011-08-19
    Description: The interpretation of the infrared excess from Alpha Lyrae as seen by the Infrared Astronomy Satellite in terms of thermal emission from a circumstellar shell of large particles follows from the recognition that small dust grains would be removed from the vicinity of the star by radiation pressure and Poynting-Robertson drag. However, this explanation is viable only if there is no resupply of small grains via mass loss from Alpha Lyr itself. Radio-continuum observations were used to constrain the stellar mass loss to less than 3.4 x 10 to the -10th solar mass/yr. The observations thus support the conclusion that the infrared excess is due to residual solid matter from the prestellar nebula.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 646-648
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  • 160
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    Observations of the low-redshift broad absorption line QSO PG 1700 + 518 - Limits on the fraction of QSOs with broad absorption lines at low redshift and the physical conditions in the broad absorption line region (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 294; L1-L5
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  • 161
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    Seyfert galaxy narrow-line regions. I - Observations of forbidden O III lambda 5007 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High-resolution (23 km/s) spectra of the forbidden O III emission line at 500.7 nm from the nuclear regions of 32 Seyfert galaxies and low-redshift QSOs have been obtained at the Smithsonian Institution/University of Arizona Multiple Mirror Telescope. The properties of the data are summarized by a group of measures which efficiently describe the entire line profiles, are stable in the presence of noise, and have easily visualized geometric meaning. The distributions of line profile measures are shown. In particular, typical forbidden O III FWHM values of 200-520 km/s (mean + or - 1 sigma) and a highly significant tendency for the lines to fall off more slowly on the blue than on the red side of the peak have been found, in agreement with previous work. Using galaxian system velocities obtained from absorption-line measurements, the distribution of differences between forbidden O III emission-line velocities and galaxian system velocities has been determined; in disagreement with previous work, this distribution has been found to be consistent with symmetry about zero difference velocity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 106-120
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  • 162
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    Where's the gas? (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The recent finding of hot interstellar hydrogen gas in elliptical galaxies is discussed. The belief held until recently that elliptics had no such gas and thus were past their star-forming stage is contradicted by new evidence obtained primarily with the X-ray images from the Einstein satellite. The hot gas is present in far greater amounts than could be accounted for by an outflowing galactic wind. The gas exists in isolated elliptics as well as in cluster members and thus is not part of the intracluster medium. It is concluded that the gas must be forming new small stars, since few massive hot stars are visible in elliptical galaxies.
    Keywords: ASTROPHYSICS
    Type: Natural History (ISSN 0028-0712); 94
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  • 163
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    Nucleus precession of periodic comet Comas Sola (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The nuclear properties of the periodic comet Comas Sola are studied based on a precession model applied previously to the periodic comets Encke, Kopff, and Giacobini-Zinner. The results imply that, for a few revolutions about the sun, Comas Sola was precessing more rapidly than any comet studied to date. An explanation is offered for this behavior in terms of a perturbation in the comet's obliquity shortly after the 1952 passage through perihelion. The equatorial radius of the nucleus is close to 1 km and its rotation period is 1.5-2.3 days, according to the model results. The calculated shape of the nucleus is compared with those of other comets studied using this technique.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 1370-138
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  • 164
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    Evidence of a hot population in the SMC/LMC bridge detected by the very wide field camera of Spacelab-1 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Deep 66-degree field photographs of the sky have been taken by the SL - 1 Very Wide Field Camera (experiment 1-ES-022) at 1650, 1930 and 2530 A, with a limiting magnitude of 9.3 at 1930 A. A 1, 2 x 2, 4 Kpc ultraviolet extension of the Shapley's wing of the Small Magellanic Cloud is revealed.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 3, 19
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  • 165
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    Effects of multiquantum transitions on molecular populations in grain-forming circumstellar environments (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Simplification of astrophysical calculations can be achieved by invoking the condition of local thermodynamic equilibrium; however, recent investigations suggest that this assumption may not be valid for certain astrophysical regions. To examine the effects of multiquantum translation to vibration transitions in expanding circumstellar envelopes, vibrational populations of the lowest 20 levels of CO have been calculated as a function of pressure and radiation density for H atom-CO collisions. Significant departure from local thermodynamic equilibrium is indicated, which implies lower dissociation rates for molecular components and a subsequent enhancement in the rate of grain formation by many orders of magnitude. Stabilization of intermediate species before they can dissociate may facilitate the formation of refractory grain cores in very hot, dilute outflows. As the present calculations indicate, laboratory measurements of state-to-state translation to vibration rates are needed for a more complete understanding of circumstellar chemistry.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 293; 463-469
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  • 166
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    The ultraviolet spectrum of the planetary nebula M3-27 (1985)
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    Publication Date: 2011-08-19
    Description: The planetary nebula M3-27 was observed in the low-dispersion mode of the IUE satellite in the region 1150 A-3200 A. A fairly strong continuum was seen to extend down to 1150 A, superposed with a relatively small number of emission lines. A high electron density is inferred from forbidden O III but regions of lower density also exist. The ultraviolet characteristics of M3-27 are compared to those of M1-2. A carbon abundance of log C = 7.72 was estimated from the semiforbidden C III nebular line for an adopted Te = 15,000 K; no emission lines of C IV 1549 A, C II 2326 A, or He II 1640 A were detected. Based on the UV observations, M3-27 would be classified as of slightly lower excitation class than M1-2 or IC 4997.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 97; 404-406
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  • 167
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    Mass outflows from young stellar objects (1985)
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    Publication Date: 2011-08-19
    Description: The process of mass loss from young stellar objects is examined in a review of recent observational investigations and theoretical models. Consideration is given to the interaction of the stellar wind with surrounding molecular clouds, the high degree of collimation seen in some embedded objects, alignment of outflows from stars embedded in the same cloud complex, initially isotropic and intrinsically anisotropic models of mass outflow, and the kinds of observations needed to determine the actual mechanisms involved.
    Keywords: ASTROPHYSICS
    Type: Comments on Modern Physics, Part C - Comments on Astrophysics (ISSN 0146-2970); 10; 179-186
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  • 168
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    Ionized polycyclic aromatic hydrocarbons and the diffuse interstellar bands (1985)
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    Publication Date: 2011-08-19
    Description: A good case has recently been made that the unidentified infrared emission features arise from positively charged, partially hydrogenated polycyclic aromatic hydrocarbons (PAHs). In this letter it is suggested that these exceedingly stable ions are also the carriers of the diffuse interstellar bands. Although a large variety of PAH isomers is possible, the more condensed forms are substantially more stable than the less condensed forms and are expected to be dominant in the harsh interstellar environment. While neutral PAHs do not absorb in the visible, their ionized counterparts do. Because of their low ionization potential, a substantial fraction of the interstellar PAHs will be ionized. Visible spectra of the most stable PAH cations isolated in glasses are compared directly to the interstellar band spectra. Although the laboratory spectra are on an extremely compressed scale and solid state shifts are present, the comparison is favorable. Since little information is available concerning the spectroscopic properties of these species in the gas phase, a considerable amount of laboratory and theoretical work is called for to test this hypothesis.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 293; L45-L48
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  • 169
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    Adsorption and recombination of hydrogen atoms on a model graphite surface (1985)
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    Publication Date: 2011-08-19
    Description: The adsorption and recombination of atomic hydrogen on a model graphite grain have been examined in a series of calculations in which a modified, iterative, extended Hueckel program was used. The hydrogen atom is found to be chemisorbed at a site with a zero-point binding energy of 0.7 eV and at an equilibrium distance of 2.25 A above the site. Despite a barrier of about 0.4 eV between adjacent sites, calculations suggest that at temperatures as low as 10 K, an H atom will tunnel through to adjacent sites in less than one nanosecond. However, a potential barrier to the recombination of two hydrogen atoms has been found which displays high sensitivity to the mutual arrangement of the two hydrogen atoms with respect to the graphite surface. Results show that at very low temperatures, recombinations can occur only by tunneling. Consistent with experiment, the region in which H2 begins to form exhibits a repulsive potential with respect to possible chemisorption of the incipient H2 entity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 293; 243-250
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  • 170
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    Photodissociation regions. I - Basic model. II - A model for the Orion photodissociation region (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A theoretical parameter study of the temperature and chemical structure of dense photodissociation regions and their resultant spectrum is presented. Models are discussed which are relevant not only to the dust and gas between molecular clouds and H II regions, but also apply to any neutral cloud illuminated by intense FUV fluxes. The models relate observed line and continuum emission from these regions to physical parameters such as the gas density and temperature, the elemental and chemical abundances, the local radiation field, and the grain properties. The results are applied to observational data from the OMC-1 region. The model shows that the observed high brightness temperature of the C I 609 microns line can be explained by emission from the C(+)/C/CO transition region. This difference with previous chemical models is due to a higher gas phase elemental abundance of carbon, to the charge exchange reactions of C(+) with S and SiO, and to carbon self-shielding.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 291; 722-754
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  • 171
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    X-ray emission from red quasars (1985)
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    Publication Date: 2011-08-19
    Description: A dozen red quasars were observed with the Einstein Observatory in order to determine their X-ray properties. The observations show that for all these sources, the infrared-optical continuum is so steep that when extrapolated to higher frequencies, it passes orders of magnitude below the measured X-ray flux. The X-ray emission is better correlated with the radio than with the infrared flux, suggesting a connection between the two. By applying the synchrotron-self-Compton model to the data, it is found that the infrared-optical region has a size of 0.01 pc or more and a magnetic field more than 0.1 G, values considerably different than are found in the radio region. Unlike other quasars, the ionizing continuum is dominated by the X-ray emission. The peculiar line ratios seen in these objects can be understood with a photoionization model, provided that the photon to gas density ratio (ionization parameter) is an order of magnitude less than in typical quasars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 291; 505-510
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  • 172
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    Multifrequency observations of blazars. I - The shape of the 1 micron to 2 millimeter continuum (1985)
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    Publication Date: 2011-08-19
    Description: Near-simultaneous measurements in 11 wavebands between 1 micron and 2 mm of a sample of 13 'blazars' are presented. These measurements represent the first comprehensive attempt to determine the infrared-to-millimeter-wave properties of this class of object, which emit the bulk of their luminosity in the far-infrared region. Most of the sources have very flat millimeter/submillimeter spectra up to the highest observed frequency. However, 3C 279 and 3C 446 show evidence of turnovers in their submillimeter spectra. The 1-4 micron spectra can be characterized by simple power laws, all steeper than -0.9; several sources, however, show evidence of spectral beaks in the 10-20 micron region, suggestive of energy losses. It is shown that the spectral properties are consistent with synchrotron emission from relativistic jets aligned close to the line of sight and the observations are discussed in relation to such models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 291; 511-517
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  • 173
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    Numerical simulation of comet nuclei. I - Water-ice comets (1985)
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    Publication Date: 2011-08-19
    Description: A one-dimensional numerical model of pure water-ice cometary nuclei is presented, and the influence of the nuclear interior as a heat reservoir on the behavior of the nuclear surface is examined. It is shown that a number of effects, including the thermal inertia due to heat stored in the core and the release of latent heat, which goes entirely into heating the adjacent layers or into sublimation on passing through a phase transition from amorphous to crystalline ice, can help to explain such characteristics as the asymmetrical lightcurve of Comet Halley. Results are given for the cases of Comet Schwassmann-Wachmann 1 and Comet Encke. Consideration is also given to the insulating effect of an evolving dust mantle. The role of this mantle in determining the surface temperature of the ice core is studied as a function of the mass fraction of the dust in the ice-dust mixture and the thermal conductivity of the nucleus. The loose-lattice model of Mendis and Brin (1977) indicates that both high dust to ice ratios and high-core conductivities inhibit mantle blowoff.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 61; 252-277
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  • 174
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    Shock evolution in the outer heliosphere - Voyager and Pioneer observations (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations are reported of 35 interplanetary shocks detected at heliocentric distances between 6.5 and 9.4 AU in mid-1980 by the Voyager 1, Voyager 2, and Pioneer 11 spacecraft. These shocks were all evidently generated by the interaction of corotating streams. Measurements of the pre- and postshock plasma parameters are used to determine the shock normals and speeds for each shock. Twelve of these 35 events are observed at all three spacecraft. The shock parameters at each spacecraft are compared to determine the time history for the 12 shocks. The single-spacecraft determinations of shock normal and speed are compared wih the results of several techniques for determining shock velocities using all three spacecraft. It is found that shocks undergo significant evolution as they travel past the three spacecraft. Every shock seen by both end spacecraft was also seen by the middle spacecraft. Shock formation possibly may be occurring at a heliocentric distance as great as 7 AU. It appears that the shock surfaces have a complex three-dimensional structure with 'ripples' on a scale of 0.001-1.0 AU.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 9454-946
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  • 175
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    Turbulence in molecular clouds - A new diagnostic tool to probe their origin (1985)
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    Publication Date: 2011-08-19
    Description: A method is presented to uncover the instability responsible for the type of turbulence observed in molecular clouds and the value of the physical parameters of the 'placental medium' from which turbulence originated. The method utilizes the observational relation between velocities and sizes of molecular clouds, together with a recent model for large-scale turbulence (constructed by Canuto and Goldman, 1985).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 294; L125-L12
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  • 176
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    Does orientation affect the smoothness of parsec-scale radio jets? (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The compact, nonthermal radio sources which are studied with very-long-baseline interferometry (VLBI) are often found to have a linear structure with a bright, nearly unresolved component at one end. This asymmetric structure is usually referred to as a 'core-jet' morphology. In some sources there are bright bumps or knots - regions of enhanced radio emission - along the 'jets', while other sources have relatively smooth, featureless jets. This paper reports the result of a study of the differences between compact radio sources with bumpy and smooth jets. It is concluded that most, if not all, of the difference in jet smoothness can be attributed to the orientation of the radio axis with respect to the line of sight. Thus, the VLBI observations do not necessarily imply that there are intrinsic differences in the smoothness of parsec-scale radio jets.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 1446-144
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  • 177
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    Pulsar magnetospheres in binary systems (1985)
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    Publication Date: 2011-08-19
    Description: The criterion for stability of a tangential discontinuity interface in a magnetized, perfectly conducting inviscid plasma is investigated by deriving the dispersion equation including the effects of both gravitational and centrifugal acceleration. The results are applied to neutron star magnetospheres in X-ray binaries. The Kelvin-Helmholtz instability appears to be important in determining whether MHD waves of large amplitude generated by instability may intermix the plasma effectively, resulting in accretion onto the whole star as suggested by Arons and Lea and leading to no X-ray pulsar behavior.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 293; 25-30
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  • 178
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    Images in the rocket ultraviolet - The initial helium abundance and distance modulus of the globular cluster M5 from photometry of horizontal-branch stars (1985)
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    Publication Date: 2011-08-19
    Description: A natural laboratory for the study of postmain-sequence evolution of low-mass (less than one solar mass) metal-poor stars is provided by globular clusters. These clusters are, therefore, a critical aid for developing an understanding of advanced stages of stellar evolution and of the chemical evolution of the Galaxy. Bohlin et al. (1983) have described a study of the postasymptotic branch star near the center of M5. The present investigation is concerned with the fainter horizontal-branch stars. The observations were made with the aid of a rocket-borne 38 cm f/9.0 Ritchey-Chretien telescope. Attention is given to payload and flight data, preflight bandpass calibration, the reduction of flight data, star selection, position measurement, photometry, the minimum observed horizontal-branch mass and inferences on mass loss, and individual UV-bright stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 687-695
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  • 179
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    Condensation onto grains in the outflows from mass-losing red giants (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In the outflows from red giants, grains are formed which are driven by radiation pressure. For the development of a model of the outflows, a detailed understanding of the interaction between the gas and dust is critical. The present investigation is concerned with condensation processes which occur after the grains nucleate near the stars. A physical process considered results from the cooling of the grains as they flow away from the star. Molecules which initially do not condense onto the grains can do so far from the star. It is shown that for some species this effect can be quite important in determining their gas-phase abundances in the outer circumstellar envelope. One of the major motivations of this investigation was provided by the desire to understand the physical conditions and molecular abundances in the outflows from the considered stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 487-493
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  • 180
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    Polycyclic aromatic hydrocarbons and the diffuse interstellar bands (1985)
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    Publication Date: 2011-08-19
    Description: This paper discusses some of the thermodynamic and spectroscopic properties of polycyclic aromatic hydrocarbons which make them attractive candidates as carriers of the Diffuse Interstellar Bands (DIBs). It is pointed out that, in the diffuse medium, many of these species will be partially hydrogenated and positively charged, and will absorb in the visible. The observed lineshapes and widths of the DIBs can be explained by rovibronic band contours and linebroadening due to internal conversion. Since little information is available concerning the spectroscopic properties of such species in the gas phase, a considerable amount of laboratory and theoretical work is needed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 146; 1, Ma; 76-80
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  • 181
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    Desorption from interstellar grains (1985)
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    Publication Date: 2011-08-19
    Description: Different desorption mechanisms from interstellar grains are considered to resolve the conflict between the observed presence of gaseous species in molecular clouds and their expected depletion onto grains. The physics of desorption is discussed with particular reference to the process of grain heating and the specific heat of the dust material. Impulsive heating by X-rays and cosmic rays is addressed. Spot heating of the grains by cosmic rays and how this can lead to desorption of mantles from very large grains is considered. It is concluded that CO depletion on grains will be small in regions with A(V) less than five from the cloud surface and n(H) less than 10,000, in agreement with observations and in contrast to expectations from pure thermal equilibrium. Even in very dense and obscured regions and in the absence of internal ultraviolet sources, the classical evaporation of CO or N2 and O2-rich mantles by cosmic rays is important.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 144; 1, Ma; 147-160
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  • 182
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    Molecular clouds in the Carina arm (1985)
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    Publication Date: 2011-08-19
    Description: From a new survey of the 2.6 mm line of CO in the southern Milky Way, 37 molecular clouds were identified along the Carina arm from l = 282 deg to 336 deg with masses generally greater than 10 to the 5th solar mass. The clouds lie approximately every 700 pc along a spiral segment that is nearly 25 kpc long and has a pitch of about 10 deg. The total mass of these clouds is 40 x 10 to the 6th solar mass, or rougly 1 x 10 to the 6th solar mass each on average. The abrupt tangent point in molecular clouds at l = 280 deg and the characteristic loop structure in the l-v diagram are unmistakable evidence of a CO spiral arm in Carina. This arm apparently connects with the northern hemisphere Sagittarius arm to form a single 10 deg spiral which extends more than two-thirds of the way around the Galaxy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 290; L15-L20
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  • 183
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    Hydrogen-like atoms on the surface of neutron stars - Intense magnetic field effects (1985)
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    Publication Date: 2011-08-19
    Description: It is known that very strong (greater than 1-TG) magnetic fields exist on the surface of some neutron stars. The properties of atoms in fields of this nature are considerably different from those of atoms in field-free regions. Because of the mixing of spherical and cylindrical symmetries, the analytical solution to the problem of a hydrogen atom in a uniform magnetic field is impossible to obtain. In this work, a variational wave function is used to describe the properties of hydrogen like atoms in intense magnetic fields including first-order relativistic effects. Special attention is given to the transition matrix elements for the 2p(0) - 1s(0) transition in Fe XXVI.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 289; 782-791
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  • 184
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    Gamma-ray burster recurrence time scales (1985)
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    Publication Date: 2011-08-19
    Description: In the decade since gamma-ray bursters (GRBs) were discovered by Klebesadel et al. (1973), many models have been proposed to explain the GRB phenomenon. A difficulty is related to the small number of predictions which would make it possible to evaluate the models. One verifiable prediction is the recurrence time scale, tau-gamma. One method to measure tau-gamma is to look for possible cases of recurrence as indicated by overlapping error boxes. The analysis considered in the present investigation is composed of three procedures. One of these involves a search through known error regions for cases where the error regions overlap. In addition, the number of overlaps expected by chance coincidence alone has been determined, and a calculation has been performed regarding the number of overlaps which are expected due to recurrence for various assumed tau-gamma and luminosity functions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 289; 490-493
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  • 185
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    Ultraviolet spectra of N, R, and S stars (1985)
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    Publication Date: 2011-08-19
    Description: Ultraviolet IUE spectra of N, R, and S stars are displayed and discussed. Carbon stars of type N have IUE spectra similar to M stars except that the Mg II lines are much weaker and low-excitation lines from neutral metals are stronger. Spectra of early R stars (R0-R3) closely resemble those of late G or early K in both lines and continuum with no significant emission lines. Late R stars (R5-R8) show spectra like late K or early M stars except that lines from low levels of excitation are stronger. Ultraviolet spectra of S stars show a wide variation in the strength of Mg II lines.
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  • 186
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    Niobium in R And (S6, 6e) and HR 1105 (S5, 3) (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Lines of the first multiplet of niobium are strong in R And and HR 1105. These lines are also present in other S stars: HR 8714, R Cam, V Cnc, R CMi, and T Sgr. They are also visible in the M stars, Beta-Peg and Mu-UMa. An approximation to the abundance ratio, Nb/Fe, has been deduced from pairs of lines having nearly equal intensity. In R And, the ratio is about 200 times the solar value. It is hoped that good plates will soon be obtained for the near infrared region, so that the significant Nb/Rb abundance ratio may be determined.
    Keywords: ASTROPHYSICS
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  • 187
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    CNO isotopes in red giant stars (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The production and distribution of the CNO nuclides is discussed in light of observed abundance ratios in red giants and in the interstellar medium. Isotope abundances have been measured in the atmospheres and in the recent ejecta of cool giants, including carbon stars, S-type stars and red supergiants as well as in oxygen-rich giants making their first ascent of the giant branch. Several of the observations suggest revision of currently accepted nuclear cross-sections and of the mixing processes operating in giant envelopes. By comparing red giant abundances with high-quality observations of the interstellar medium, conclusions are reached about the contribution of intermediate-mass stars to galactic nuclear evolution. The three oxygen isotopes, O-16, -17 and -18, are particularly valuable for such comparison because they reflect three different stages of stellar nucleosynthesis. One remarkable result comes from observations of O-17/O-18 in several classes of red giant stars. The observed range of values for red giants excludes the entire range of values seen in interstellar molecular clouds. Furthermore, both the observations of stars and interstellar clouds exclude the isotopic ratio found in the solar system.
    Keywords: ASTROPHYSICS
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  • 188
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    A wide latitude CO survey of molecular clouds in the III galactic quadrant (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Molecular clouds in the third galactic quadrant from 180-280 galactic longitude were surveyed in the 115.271 GHz line of CO at an angular resolution of 0.5 deg. In galactic latitude the survey covers from b = -5 to +5 deg, with a few extensions to higher latitudes. A preliminary analysis of the data allowed the determination of distances and masses of at least 30 molecular clouds related to the Perseus arm and to the Cygnus, or outer, arm. The studied clouds are located between 2.5 kpc and 10.7 kpc from the sun with most of the masses between 30,000-700,000 solar masses, and only three up to two million solar masses. The most interesting result comes from the distribution of the clouds distance from the galactic plane that indicates a warp in the arms to which these clouds belong.
    Keywords: ASTROPHYSICS
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  • 189
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    Radio polarization characteristics of two RS CVn binaries (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The results of multifrequency epoch VLA observations of polarized radio emission from the nearby active RS CVn binaries UX Arietis and HR 1099 are reported. For both systems, there is an excellent correlation between handedness of circular polarization and frequency. Helicity reversal is almost always seen between 1.4 and 5.0 GHz, possibly due to optical depth effects. There may also be an anticorrelation between total intensity and fractional circular polarization, especially at 5 GHz. This is consistent with models in which intense flares are associated with compact selfabsorbed synchrotron sources, while the quiescent emission arises from larger gyrosynchrotron-emitting plasma.
    Keywords: ASTROPHYSICS
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  • 190
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    Dust emission of Comet Halley at large heliocentric distances (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Comet Halley is currently approaching the inner solar system. Four spacecrafts (NASA's spacecraft, two Russian Vega probes and the Japanese MS-T5 spacecraft) have already been launched to encounter the comet in March 1986. Two additional Halley probes (the European Giotto spacecraft and another Japanese Planet-A probe) will be launched in mid-85 to join the armada. Observations of dust emissions from Halley's Comet are discussed. The evaporation of cometary ices causes the emission of particulates from the nucleus. These observations will be used to determine the fly-by strategy of the Giotto spacecraft by taking into account the distribution of dust in the vicinity of the nucleus and the associated hazard for the space mission.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst. 16th Lunar and Planetary Sci. Conf.; p 28-31
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  • 191
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    Interstellar Al-26 and excess Mg-26 (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Evidence of a possible supernova explosion that occured very near the Earth is presented by the presence of radioactive 26 Aluminum (26 Al). The time of the supernova explosion is placed at approximately 100,000 years ago and is partially supported by cosmic gamma ray measurements from both HEAO 3 and the Solar Maximum Mission.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst. 16th Lunar and Planetary Sci. Conf.; p 9-11
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  • 192
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    Mining cosmic dust from the blue ice lakes of Greenland (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Extraterrestrial material, most of which invisible settles to Earth's surface as dust particles smaller than a millimeter in size were investigated. Particles of 1/10 millimeter size fall at a rate of one/sq m/yr collection of extraterrestrial dust is important because the recovered cosmic dust particles can provide important information about comets. Comets are the most important source of dust in the solar system and they are probably the major source of extraterrestrial dust that is collectable at the Earth's surface. A new collection site for cosmic dust, in an environment where degradation by weathering is minimal is reported. It is found that the blue ice lakes on the Greenland ice cap provide an ideal location for collection of extraterrestrial dust particles larger than 0.1 mm in size. It is found that the lakes contain large amounts of cosmic dust which is much better preserved than similar particles recovered from the ocean floor.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst. 16th Lunar and Planetary Sci. Conf.; p 51-53
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  • 193
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    Periodic cometary showers: Real or imaginary? (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Since the initial reports in 1980, a considerable body of chemical and physical evidence has been accumulated to indicate that a major impact event occurred on earth 65 million years ago. The effects of this event were global in extent and have been suggested as the cause of the sudden demise or mass extinction of a large percentage of life, including the dinosaurs, at the end of the geologic time period known as the Cretaceous. Recent statistical analyses of extinctions in the marine faunal record for the last 250 million years have suggested that mass extinctions may occur with a periodicity of every 26 to 30 million years. Following these results, other workers have attempted to demonstrate that these extinction events, like that at the end of the Cretaceous, are temporally correlated with large impact events. A recent scenario suggests that they are the result of periodic showers of comets produced by either the passage of the solar system through the galactic plane or by perturbations of the cometary cloud in the outer solar system by a, as yet unseen, solar companion. This hypothesized solar companion has been given the name Nemesis.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst. 16th Lunar and Planetary Sci. Conf.; p 24-27
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  • 194
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    A spectacular nitrogen isotope anomaly in Bencubbin (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of isotopic measurements on an unusual stony-iron meteorite named Bencubbin, which was found in Western Australia in 1930, are reported. Nitrogen from both the metallic and stony parts of the Bencubbin meteorite was analyzed, and in both materials large excesses of (15)N were found, resulting in values of the (14)N/(15)N abundance ratios as low as 137. That is, (15)N is enriched in Bencubbin by about a factor of two relative to terrestrial nitrogen. This is the largest (15)N enrichment of any known natural material. The effect is so large that chemical processes are probably inadequate to account for it. Nuclear processes which may be responsible for the anomalous isotope abundance are discussed.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst. 16th Lunar and Planetary Sci. Conf.; p 71-73
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  • 195
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    Protostars and planets II (1985)
    In:  Other Sources
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    Publication Date: 2016-03-09
    Description: Various papers on the formation of stars and planets are presented. The general topics addressed include: molecular clouds and star formation, young stellar objects and circumstellar disks, chemistry and grains in molecular clouds and the solar nebula, formation of giant planets, and models of the solar nebula and other planetary systems. Individual papers address: molecular cloud cores, physical conditions in isolated dark globules, rotation in dark clouds, and turbulence in molecular clouds. Also discussed are: fragmentation and hierarchical structure in the interstellar medium, formation of bound stellar clusters, ambient radiation field of young solar systems, and magnetic fields.
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  • 196
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    Instellar Gas Experiment (IGE): Testing interstellar gas particles to provide information on the processes of nucleosynthesis in the big bang stars and supernova (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Interstellar Gas Experiment (IGE) is designed to collect particles of the interstellar gas - a wind of interstellar media particles moving in the vicinity of the solar system. These particles will be returned to earth where the isotopic ratios of the noble gases among these particles will be measured. IGE was designed and programmed to expose 7 sets of six copper-beryllium metallic collecting foils to the flux of neutral interstellar gas particles which penetrate the heliosphere to the vicinity of the earth's orbit. These particles are trapped in the collecting foils and will be returned to earth for mass-spectrographic analysis when Long Duration Exposure Facility (LDEF) on which IGE was launched, is recovered.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-186713 , NAS 1.26:186713
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  • 197
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    Radio continuum emission from T Tauri stars and associated structures (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The current status of radio continuum observations of low mass, pre-main sequence stars (T Tauri stars) is discussed. The majority of T Tauri radio sources have been detected by the VLA telescope and a guide to both these and earlier observations is presented. Both nonthermal and thermal radio continuum emission has been detected from T Tauri stars. The likely emission processes and specific examples of their occurrence are outlined. The detected radio sources are often associated with the surroundings of the star, such as bipolar flows or diffuse extended optical nebulosity, rather than regions very close to the stellar surface. Only recently have radio continuum observations reached a sensitivity appropriate to the expected level of thermal free-free emission from the winds of ordinary T Tauri stars and it is possible that many more radio sources will now be found associated with these stars.
    Keywords: ASTROPHYSICS
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  • 198
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    Evolution and interaction of large interplanetary streams (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer simulation for the evolution and interaction of large interplanetary streams based on multi-spacecraft observations and an unsteady, one-dimensional MHD model is presented. Two events, each observed by two or more spacecraft separated by a distance of the order of 10 AU, were studied. The first simulation is based on the plasma and magnetic field observations made by two radially-aligned spacecraft. The second simulation is based on an event observed first by Helios-1 in May 1980 near 0.6 AU and later by Voyager-1 in June 1980 at 8.1 AU. These examples show that the dynamical evolution of large-scale solar wind structures is dominated by the shock process, including the formation, collision, and merging of shocks. The interaction of shocks with stream structures also causes a drastic decrease in the amplitude of the solar wind speed variation with increasing heliocentric distance, and as a result of interactions there is a large variation of shock-strengths and shock-speeds. The simulation results shed light on the interpretation for the interaction and evolution of large interplanetary streams. Observations were made along a few limited trajectories, but simulation results can supplement these by providing the detailed evolution process for large-scale solar wind structures in the vast region not directly observed. The use of a quantitative nonlinear simulation model including shock merging process is crucial in the interpretation of data obtained in the outer heliosphere.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-86192 , NAS 1.15:86192
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  • 199
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    Magnetohydrodynamic model of the Crab Nebula and its radiation (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The interaction of the Crab pulsar with its surrounding nebula is modeled as a steady state, spherically symmetric relativistic wind which is confined by the outer layers of the supernova remnant. The pulsar wind is assumed to contain only positrons and electrons, and is terminated by a strong shock at a distance of 10 arcseconds from the pulsar, at the outer edge of the underluminous region. Down-stream of the shock, the flow decelerates and increases its pressure in order to match the boundary conditions imposed by outer nebula. Consistent flow solutions can be found if the magnetic luminosity of the pulsar wind is about 0.3 percent of its particle luminosity. The immediate postshock plasma is modeled as a power law distribution whose density and pressure moments satisfy the strong shock Rankine-Hugoniot relations. Using the downstream flow solution, the synchrotron continuum is calculated. The parameters of the pulsar wind and assumed power law spectral index are adjusted until the calculated total synchrotron power and the spectral distribution of the nebular continuum from optical to gamma-rays, are in reasonable accord with observations.
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  • 200
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    Solar-geophysical data number 494, October 1985, Part 2: (Comprehensive reports). Data for April 1985, January-June 1984 and miscellanea (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Contents include: detailed index for 1985; data for April 1985 (Meudon carte synoptique, solar radio bursts at fixed frequencies, solar X-ray radiation form GOES satellite, mass ejections from the sun, active prominences and filaments); data for January to June 1984 (solar flares January 1984, solar flares February 1984, solar flares March l984, solar flares April 1984, solar flares May 1984, solar flares June 1984, and number of flates August 1966 to June 1984); and miscellaneous data (interplanetary solar wind July 1984 to March 1985, errata solar X-rays event list January 1985).
    Keywords: ASTROPHYSICS
    Type: NASA-CR-176676 , NAS 1.26:176676 , PB86-143252 , SGD-494-PT-2
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