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  • 1
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    The spectrum of HM Sagittae - A planetary nebula excited by a Wolf-Rayet Star (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 19; 3, 19; 1978
    Format: text
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  • 2
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    Coordinated photometric and spectroscopic observations of strong extragalactic 90 GHz sources (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Nearly simultaneous radio and infrared-optical observations were obtained for several extragalactic radio sources which are strong at 90 GHz. The spectral-flux distributions are generally peaked or flat over the radio portion of the spectrum with a steeper, power-law behavior at infrared-optical frequencies. For all sources, the radio and infrared-optical portions of the spectral-flux distributions can be smoothly joined by physically sensible interpolations over the spectral gap, although spectral breaks are required. For many of the sources, this is consistent with a common (synchrotron) origin of the radio, millimeter, and infrared-optical radiation. However, proof, in terms of correlated temporal variations and polarization properties, is still generally lacking.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 224
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  • 3
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    Properties of the 2-6 keV pulse profiles of Hercules X-1 (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 4
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    Ortho- and para-hydrogen in dense clouds, protoplanets, and planetary atmospheres (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: If ortho- and para-hydrogen achieve a thermal ratio on dynamical time scales in a molecular hydrogen cloud, then the specific heat is high enough in the temperature range 35-70 K to possibly induce hydrodynamic collapse. The ortho-para ratio in many interstellar cloud fragments is expected to meet this condition. The same may have been true for the primitive solar nebula. Detailed hydrodynamic and hydrostatic calculations are presented that show the effects of the assumed ortho-para ratio on the evolution of Jupiter during its protoplanetary phase. Some possible consequences of a thermalized ortho-para ratio in the atmospheres of the giant planets are also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 223
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  • 5
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    Bar-driven spiral waves in disk galaxies (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The response of rotating disks of gas to barlike perturbations in galactic gravitational fields is investigated. In particular, two-dimensional time-dependent numerical hydrodynamical calculations have been performed in order to determine the steady-state response of disks of gas to rotating barlike perturbations. Two types of barlike perturbations are considered: oval distortions in the axisymmetric gravitational field of the disk, and heterogeneous prolate spheroids. The calculations reveal that in the absence of gaseous self-gravity, a viscous differentially rotating disk of gas responds to a rotating barlike perturbation by forming a central gas bar with two trailing spiral waves. The local phase of the gas response is primarily a function of the number and spacing of the principal resonances in the disk. This result may be understood in terms of particle orbit theory. The gas response to barlike perturbations also depends on the relative strength and the effective axial ratio of the bar. In these calculations strong narrow bars produce offset shocks in the central gas bar. These shocks correspond in position to the long narrow dust lanes observed in many barred spiral galaxies.
    Keywords: ASTROPHYSICS
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  • 6
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    Ultraviolet observations of cool stars. VII - Local interstellar hydrogen and deuterium Lyman-alpha (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: High-resolution Copernicus spectra of Epsilon Eri and Epsilon Ind containing interstellar hydrogen and deuterium L-alpha absorption lines are presented, reduced, and analyzed. Parameters of the interstellar hydrogen and deuterium toward these two stars are derived independently, without any assumptions concerning the D/H ratio. Copernicus spectra of Alpha Aur and Alpha Cen A are reanalyzed, and limits on the D/H number-density ratio consistent with the data for all four stars are considered. A comparison of the present estimates for the parameters of the local interstellar medium with those obtained by other techniques shows that there is no compelling evidence for significant variations in the hydrogen density and D/H ratio in the local interstellar medium. On this basis the hypothesis of an approaching local interstellar cloud proposed by Vidal-Madjar et al. (1978) is rejected
    Keywords: ASTROPHYSICS
    Type: PB-289017 , Astrophysical Journal; vol. 225
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  • 7
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    Correlated photometric and polarimetric phenomena in AM Herculis (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Via simultaneous multicolor photometry and polarimetry of AM Herculis, we find correlations among polarization, flux, and color in the V and I bands in periodic and nonperiodic (i.e., flickering) activity. The primary minimum observed in both bands is accompanied by a blueward shift of the (B - R) color and a decrease in the absolute value of the percent circular polarization in the V band. Outside primary minimum, peaks of flickering activity tend to be associated with an increase in the absolute value of the circular polarization and the concurrent reddening of the (B - R) and (R - I) colors. The visual light curve of AM Her can be explained by a flickering, circularly polarized light source which is obscured at primary minimum, and is redder than the total system color in the URVRI bands.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 225
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  • 8
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    Collisional excitation of interstellar formaldehyde (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Previous calculations for rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Rates for para-H2CO have also been computed. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%. Excitation of formaldehyde by collisions with H2 molecules is also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 37; July 197
    Format: text
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  • 9
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    Photometry of AM Herculis - A slow optical pulsar (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Multicolor photometry of the X-ray binary AM Her suggests that the red component of the optical flux is closely related to the source of optical circular polarization in the system. It is concluded from the periodic modulation of flux in the U through R bands, which is particularly well-defined when plotted as color curves, that the primary and secondary minima are neither eclipses by a secondary star nor eclipses by a hot spot. It is suggested that the primary minimum in the visual light curve is the eclipse of a region of intense optical emission in the magnetic field near the surface of a degenerate dwarf by that dwarf itself.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
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  • 10
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    CNO abundances and hydrodynamic studies of the Nova outburst. V - 1.00-solar-mass models with small mass envelopes (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper reports on an investigation into the consequences of thermonuclear runaways in accreted hydrogen envelopes of 100 millionths of a solar mass on 1-solar-mass white dwarfs. These evolutionary sequences predict that from 10 to 50 millionths of a solar mass will be ejected with speeds from 300 to 3800 km/s (kinetic energies of 10 to the 44th-45th power ergs). Absolute visual magnitudes as high as -8.1 are attained, well within the observed range for fast novae. In addition, the shapes of the theoretical light curves are more reminiscent of an observed fast-nova light curve than those in earlier studies. The ejected material is strongly enhanced in the products of incomplete CNO burning; the most abundant of the ejected nuclei is C-13, followed by N-14 and C-12. The differences from previous studies are attributable to the lower peak temperatures reached in these sequences. These models also produce a large overabundance of Li-7, suggesting that novae may represent significant contributors to the galactic enrichment of this nucleus.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 226
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