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  • ASTROPHYSICS  (459)
  • SOLAR PHYSICS  (258)
  • 1995-1999
  • 1980-1984
  • 1975-1979  (717)
  • 1976  (717)
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Years
  • 1995-1999
  • 1980-1984
  • 1975-1979  (717)
Year
  • 1
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    Some basic considerations of measurements involving collimated direct sunlight (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: For abstract, see N77-26622.
    Keywords: SOLAR PHYSICS
    Type: Terrest. Photovoltaic Meas., 2; p 233-246
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  • 2
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    The solar spectrum at typical clear weather days (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The solar spectrum in the range of 300 is less than lambda is less than 1500nm is given for five typical clear weather days. These days are selected to represent typical seasonal conditions in respect to airmass water vapor, ozone, and turbidity. Present data are reviewed, and specific conditions are selected. The spectral distribution of the irradiance is given for the direct component, the scattered skylight, the total flux on a horizontal surface, and the flux on an inclined surface normal to the direct beam.
    Keywords: SOLAR PHYSICS
    Type: NASA. Lewis Res. Center Terrest. Photovoltaic Meas., 2; p 17-58
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  • 3
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    Monitoring solar radiation: The ERDA program (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: An overview of the Energy Research and Development Administration planned insolation data network is described. The design of the network is predicated on an analysis and definition of user requirements. Research and analysis projects covering data collection, forecasting and extrapolation are presented.
    Keywords: SOLAR PHYSICS
    Type: NASA. Lewis Res. Center Terrest. Photovoltaic Meas., 2; p 1-17
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  • 4
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    The long term variability of HDE 226868 = Cygnus X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Investigation of blue-sensitive photographs of HDE 226868 = Cygnus X-1 reveal no (+ or - 0.06 mag) long-term changes in brightness since the beginning of the century nor any abrupt intensity changes similar to what was observed at X-ray and radio frequencies. From the double sinusoidal fluctuation with 5.6 day period, an attempt is made to derive a more precise value for the orbital period, but problems are encountered and discussed. There exists evidence that the amplitude of the orbital fluctuations is increasing slowly with time.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 513-520
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  • 5
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    The interacting binary SCO X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Spectroscopic observations of Sco X-1 show conclusively that the emission lines vary in radial velocity with a period of .787 sup d + or - .006 and a full range of approximately 120 km/s. The period is identical to that found by Gottleib et al (1975) from photometric data; light minimum occurs when the emission line region is at superior conjunction. The observations indicate that the emission lines originate in an accretion disk surrounding a neutron star which is orbiting about a normal, although somewhat evolved companion. The light variation is due to a heating effect on the non degenerate star, viewed at a small inclination angle.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 683-690
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  • 6
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    Evidence for a 17d periodicity from Cyg X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Data which indicate a periodicity of 17d from Cyg X-3 are reviewed. The data are taken from the Ariel 5 satellite All-Sky Monitor and the Sky Survey Experiment.
    Keywords: ASTROPHYSICS
    Type: X-ray Binaries; p 245-253
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  • 7
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    Her X-1 spectral evidence for a strong magnetic field (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The steep high energy cutoff observed in the spectrum for Her X-1 is analyzed in terms of the severely modified Thomson scattering that dominates the radiative transfer in a highly magnetized plasma near the surface of a neutron star. The data are shown to indicate a field of about 10 to the 13th power G near the magnetic poles and the stopping of accreting matter by nuclear collisions in the neighboring plasma.
    Keywords: ASTROPHYSICS
    Type: X-ray Binaries; p 113-118
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  • 8
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    Soft X-rays from Her X-1 during the off phase (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Weak 0.28-keV radiation was observed from Her X-1 5 days before turn-on in the 35 day cycle. The observations were made from an Aerobee rocket. The 0.28-keV intensity is about 1/25 that observed during the on phase. Some evidence for X-rays above 1 keV is also present, and it is possible that the spectrum is different only in intensity from the spectrum in the on phase. The radiation may be X-rays from the vicinity of the neutron star, scattered by ionized material in the inner accretion disk, or may be thermal radiation from the inner accretion disk, or both.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 127-139
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  • 9
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    An X-ray determination of the orbital elements of 3U 0900-40 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The orbital elements of the 3U 0900-40 binary system were determined by measuring the variations in the arrival times of the 283-second X-ray pulses. The best-fit values of the system parameters and their 95% confidence limits are listed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 661-667
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  • 10
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    Mass determination for the X-ray binary system Vela X-1 (equals 3U 0900-40) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: From a radial velocity study of lines of He I and the heavier ions of HD 77581 (=Vela X-1), orbital elements for this X-ray binary system are derived. Together with the orbital elements given by Rappaport and McClintock from X-ray pulsar results, this enables determination of masses for both the X-ray and the early type supergiant component.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 643-657
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  • 11
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    The 'other' galactic X-ray sources (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: There is a standard model for X-ray sources comprising a binary system containing a compact star and powered by mass accretion. It can be argued that the majority and perhaps all the galactic X-ray sources are of this kind. Three kinds of sources which may be qualitatively different from these are discussed: namely, low luminosity sources such as 3U0352 + 30, the sources associated with the globular clusters, and the transient X-ray sources.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 669-676
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  • 12
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    The broad emission features in 'wake' in HD 153919 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: It is shown that the broad emission features in the spectrum of HD 153919 are associated with the X-ray secondary and not significantly with the primary star. When the primary is at maximum velocity towards us, the HeI line lambda 4471 develops a blue shifted secondary component with a velocity of -470 km/sec relative to the primary.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 569-574
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  • 13
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    Effects of radiation pressure on the equipotential surfaces in X-ray binaries (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Equipotential surfaces incorporating the effect of radiation pressure were computed for the X-ray binaries Cen X-3, Cyg X-1 = HDE 226868, Vela XR-1 = 3U 0900-40 = HD 77581, and 3U 1700-37 = HD 153919. The topology of the equipotential surfaces is significantly affected by radiation pressure. In particular, the so-called critical Roche (Jacobian) lobes, the traditional figure 8's, do not exist. The effects of these results on modeling X-ray binaries are discussed.
    Keywords: ASTROPHYSICS
    Type: X-ray Binaries; p 499-511
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  • 14
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    Absorption dips at low X-ray energies in Cygnus X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Absorbing material in Cygnus X-1 jitters near the line joining the two stars, out of the orbital plane is described. Three looks with the Copernicus satellite at Cygnus X-1 have produced four examples of absorption dips (decreases in the 2 to 7 keV flux from Cygnus X-1 with an increase of spectral hardness consistent with photoelectric absorption).
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 425-427
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  • 15
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    The May 1975 transient radio event in Cyg X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Radio observations of Cyg X-1 (HDE 226868) taken during the period May-June 1975 at 2,695 and 8,085 MHz are presented and discussed in the context of both the previous four years of data at these frequencies and subsequent data for September-October 1975. The data show that the radio event was a transient one with a time scale of the order of a few to several weeks, and that the observed radio decay was qualitatively similar to the observed decay of the enhanced X-ray state.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 495-497
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  • 16
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    The galactic distribution (in radius and Z) of interstellar molecular hydrogen (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Observations of the galactic longitude and latitude distributions of gamma = 2.6 mm CO emission are presented. Analysis of this spectral line data yields the large scale distribution of molecular clouds in the galactic disk and their z-distribution out of the disk. Strong maxima in the number of molecular clouds occur in the galactic nucleus and at galactic radii 4-8 kpc. The peak at 4-8 kpc correlates well with a region of enhanced 100 Mev gamma ray emissivity. This correlation strongly supports the conclusion that the gamma rays are produced as a result of cosmic ray interactions in molecular H2 clouds rather than HI. One important implication of this is that the interstellar magnetic field lines to which cosmic rays are confined must therefore not be excluded from these dense clouds. The width of the cloud layer perpendicular to galactic plane between half density points is 105 + or - 15 pc near the 5.5 kpc peak. The total mass of molecular gas in the interior of the galaxy exceeds that of atomic hydrogen.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 163-176
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  • 17
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    Artificial solar eclipse experiment MA-148 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: On July 19, 1975, the Apollo spacecraft successfully occulted the solar disk from the field of view of a camera mounted in the Soyuz spacecraft while performing a spacecraft separation maneuver to permit the outer solar corona to be viewable by the Soyuz camera. The camera operated automatically, and 55 frames were developed for scientific analysis.
    Keywords: SOLAR PHYSICS
    Type: Apollo-Soyuz Test Project; 5 p
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  • 18
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    Infrared astronomy and high energy astrophysics (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Observations of the diffuse far infrared flux from the galactic plane as well as far infrared measurements of the properties of dense molecular clouds, when combined with recent high-energy gamma ray measurements and radio observations of carbon monoxide, can yield new information about the total mass of molecular clouds, the large scale structure of the inner galaxy, and the density of cosmic rays. These observations are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 222-238
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  • 19
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    Stratospheric aerosol measurement experiment MA-007 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Apollo Soyuz Test Project Stratospheric Aerosol Measurement Experiment was flown to demonstrate that direct solar occultation measurements by photometers and photographs can be used for defining stratospheric aerosol concentrations. Supporting ground truth data were provided by laser radar and balloon borne dustsonde. Initial results show a significant difference in aerosol concentrations between the Northern and Southern Hemispheres.
    Keywords: SOLAR PHYSICS
    Type: Apollo-Soyuz Test Project; 8 p
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  • 20
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    Ultraviolet observations of local gas (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: From satellite measurements of ultraviolet spectra of stars, an average density of approximately 1.1/cu cm for hydrogen atoms, in both atomic and molecular form, is estimated for regions of space along the galactic plane within about 1 kpc of the sun. About 20% of the atoms are bound in molecular form although this figure is uncertain since the ultraviolet measurements avoid the very dense interstellar clouds. Discrete values for this percentage are observed to vary markedly; regions with less than average density seem to have fractional abundances of H2 several orders of magnitude lower than average. A ratio of CO/H is observed for regions in front of stars observed by the Copernicus satellite.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 239-263
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  • 21
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    Remarks on the overall distribution of hydrogen in the galactic disk (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Several current problems concerning the overall distribution of hydrogen in the galaxy are discussed in general terms. These problems include the degree of saturation characterizing low-latitude emission observations of HI, and the optical-depth corrections to the derived column and volume densities; the amount of fine-scale velocity and spatial structure diluted by the instrumental limitations of the presently available surveys; and the general problem of detailed mapping of the HI in the galaxy. Comparison is made between the distribution of HI and that of CO and several other galactic tracers. The galactic disk as defined by atomic hydrogen has a diameter fully twice as large as that defined by the ionized and molecular states of hydrogen, as well as by other molecules, supernova remnants, pulsars, gamma radiation, synchroton radiation, and the youngest stars. It is also less confined to the galactic equator than most of the other constituents. The degree of small-scale structure apparent in the molecular observations is much greater than in the HI observations. Parameters describing the small-scale structure were determined using Monte Carlo techniques to simulate the observations.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 177-205
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  • 22
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    Density wave theory (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The prospect that density waves and galactic shock waves are present on the large-scale in disk-shaped galaxies has received support in recent years from both theoretical and observational studies. Large-scale galactic shock waves in the interstellar gas are suggested to play an important, governing role in star formation, molecule formation, and the degree of development of spiral structure. Through the dynamics of the interstellar gas and the galactic shock wave phenomenon, a new insight into the physical basis underlying the morphological classification system of galaxies is suggested.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 128-162
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  • 23
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    The X-ray variability of Vela X-1 (3U 0900-40) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: From observations of Vela X-1 with the MSSL 2.5-7.5 keV detector onboard Copernicus, the behavior of the source can be characterized by three phases: (1) high intensity, (2) low intensity, and (3) eclipse. Combining data from the 1972 Uhuru observations with eclipse observation yields a binary period of 8.963 + or - 0.001 days with zero phase on 1975 Feb. 6.97 + or - 0.04 UT. The low intensity phase is interpreted as being due to increased absorption in an accretion wake traveling across the line of sight (the spectral slope remains relatively constant throughout the cycle). Another period of enhanced absorption immediately after exit from eclipse may be due to a bow shock. Comparison of the two observations suggests that these structures vary from cycle to cycle and, since the orbital period is long, probably during each cycle.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 629-642
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  • 24
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    Short time transient periodicities from Cyg X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The temporal behavior of three new events of modulated optical emission from Cyg X1, detected in July 1975, is presented. Short time periodicities in the optical band are investigated. Single photon pulses from the photomultiplier are recorded on magnetic tape together with a very accurate 1 kHz reference frequency. During playback of the tape, the reference signal gives a 1 ms timing to a scaler interfaced with a small processor and the number of photon per millisecond is recorded on a digital tape.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 485-492
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  • 25
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    DSS 14 operating noise temperature during Helios 1 near-sun tracking (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: When spacecraft are tracked near the line-of-sight of the sun, the ground antenna sidelobes see the solar noise. The solar noise increases the ground system operating noise temperature and degrades the downlink RF reception performance. At specific antenna azimuthal angles relative to the sun, noise peaks and nulls occur periodically throughout a day's tracking pass due to the quadripod support leg-generated sidelobes. This article documents this effect while tracking Helios 1, illustrates the time of the peaks, and compares the predicted time of the noise temperature peaks with the measured data.
    Keywords: SOLAR PHYSICS
    Type: The Deep Space Network; p 68-76
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  • 26
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    The solar wind and its influence on the atmospheres of moon, Mercury and Venus (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The solar wind is expected to have an important influence on the atmospheres of the moon, Mercury and Venus and therefore a brief outline of solar wind theory is presented along with the predicted properties of the wind at the orbits of these planets. Since the atmospheres of the moon and possibly Mercury are formed primarily by solar wind accretion, we present the latest accretion models for these bodies. The expected role the solar wind plays on both the ionization and termination of the ionosphere of Venus is discussed.
    Keywords: SOLAR PHYSICS
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  • 27
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    The solar brightness temperature at millimeter wavelengths (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Measurements of the brightness temperature of the sun near 36 GHz and 93 GHz were made using the new moon as a calibration source. Provided the brightness temperature of the moon is known and all measurements are reduced to the same zenith angle, a simple expression can be used for the sun-to-new moon ratio which is independent of antenna gain, atmospheric absorption and reemission, and radiometer calibration constants. This ratio was measured near 36 GHz and at two frequencies near 93 GHz with a Dicke switched superheterodyne radiometer system and a 2.4 m Cassegrain antenna. The slopes of the solar brightness temperature spectrum based on these ratios were measured. The absolute solar brightness spectrum derived from all current available measurements supplemented by the present ones is also plotted and discussed.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 48; May 1976
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  • 28
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    Can Malin's gravitational-field equations be modified to obtain a viable theory of gravity (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Malin's (1975) gravitational theory, which was recently shown by Lindblom and Nester (1975) to be incorrect, is modified by means of a recently proposed method for obtaining viable gravitational theories. The resulting self-consistent theory, which is in effect a Rastall-type modification of the Einstein theory, exhibits nonconservation of momentum, yet agrees with all experimental limits known to date within the post-Newtonian approximation framework.
    Keywords: ASTROPHYSICS
    Type: Nuovo Cimento; vol. 35B
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  • 29
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    2-4 micron spectrophotometric observations of compact H II regions (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectrophotometric observations from 2 to 4 microns of the compact H II regions W51-IRS 2, K3-50, and NGC 7538 are reported. Spectral features observed include hydrogen recombination lines and an absorption attributed to interstellar ice. Extinctions to the various sources are derived based on the observed hydrogen lines and radio fluxes. Thermal dust emission is found to dominate free-free and bound-free emission for wavelengths not less than 2 microns. The ice absorption is analyzed and compared with the extinction and 10 microns silicate absorption. A 3.3 micron emission feature (potentially due to the same material as in NGC 7027) was observed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 1
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  • 30
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    Interstellar cloud evolution and the abundance of formaldehyde (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The time scale for essentially complete conversion of C(+) to CO in interstellar clouds can be comparable to, or greater than, dynamical time scales for evolution, therefore suggesting steady state time independent abundances to be inappropriate. The solutions for the time-dependent carbon chemistry in dense clouds, with density not less than 500/cu cm, indicate that significant amounts of neutral carbon will be present throughout a cloud's lifetime. These nonequilibrium values of C I can explain the relatively large abundances observed for formaldehyde, isotopes of carbon monoxide, and other trace molecules
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 1
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  • 31
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    Emission object in Orion (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The note draws attention to a structural feature in the Orion nebula, consisting of a parachute-shaped object converging on 64 Orionis, noted on H alpha photographs of the Orion nebula taken with the 76-cm Allegheny refractor. The same feature shows up clearly on a photograph taken in 1909 with the Mount Wilson 152-cm reflector, and on a photograph taken with the Palomar 5-m reflector. Measurements made on these three plates indicate a possible expansion of the object of about 3.6 seconds of arc per century, corresponding to a tangential velocity of about 90 to 100 km/sec. If the expansion continued at a linear rate, an explosive event may have occurred approximately 900 years ago.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 88
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  • 32
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    Evidence for the regulation of solar wind heat flux at 1 AU (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observational evidence favoring the local regulation of solar-wind heat flux at 1 AU is reviewed, and four months of IMP 6 plasma and magnetic-field data are merged and analyzed in order to investigate what might be regulating the heat flux. A statistical analysis of the data shows that the solar-wind Alfven speed is probably regulating the heat flux locally at 1 AU and that the Alfven speed, the velocity difference between the peak of low-energy electrons and the bulk plasma velocity, and the solar-wind velocity component projected along the local spiral angle are statistically well correlated for Alfven speeds not exceeding about 70 km/s. A time-series analysis of the data indicates that only the Alfven speed and the velocity difference between the peak of low-energy electrons and the bulk plasma velocity are well correlated both qualitatively and quantitatively on a microscopic time scale. It is strongly suggested that, at times, the solar-wind heat flux is locally regulated by the magnitude of the Alfven speed at 1 AU. Uncertainties in the results are discussed.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 81; Oct. 1
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  • 33
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    High-speed solar wind flow parameters at 1 AU (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Nineteen high-speed solar-wind streams observed at 1 AU between March 1971 and July 1974 are studied to develop a more realistic set of constraints for theories on such streams. The streams were chosen because their speeds exceeded 650 km/s for at least several consecutive three-hour periods and because their properties met certain other criteria. A comparison of average stream parameters with predictions of existing steady-state models shows that no single model is adequate to explain the observations. In particular, it is found that no existing model consistent with reasonable coronal conditions predicts the particle fluxes, the convected proton bulk-flow-energy fluxes, and the convected proton enthalpy fluxes observed at 1 AU when the flow speed exceeds 650 km/s.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 81; Oct. 1
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  • 34
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    A new interpretation of luminous blue stars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A major revision of current theoretical ideas about the brightest blue stars must be made if Carson's (1976) radiative opacities are adopted in stellar models. Unlike earlier opacities, these exhibit a large 'bump' due to CNO ionization, which leads to very strong central condensation, convective instability, and pulsational instability in hot diffuse stellar envelopes. Despite a number of theoretical uncertainties, the new picture of the structure of very luminous stars is reasonably successful in accounting for a variety of previously unexplained observations. The stellar models for the phase of core hydrogen burning predict large radii and rather cool effective temperatures for O stars and a spreading out of the main-sequence band in the H-R diagram toward luminous cool supergiants for masses higher than about 20 solar masses. In massive X-ray binary systems, circular orbits and supergiant-like visual companions are expected to be quite common. Long-period variability is predicted to exist for massive blue supergiants of luminosity class Ia. The models for helium stars predict large radii and rather cool effective temperatures for Wolf-Rayet stars, as well as multimodal pulsational instability and, possibly, surface turbulence for these stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Nov. 1
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  • 35
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    Forbidden transition probabilities for ground terms of ions with p or p5 configurations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Forbidden transition probabilities are given for ground term transitions of ions in the isoelectronic sequences with outer configurations 2s2 2p (B I), 2p5 (F I), 3s2 3p (Al I), and 3p5 (Cl I). Tables give, for each ion, the ground term interval, the associated wavelength, the quadrupole radial integral, the electric quadrupole transition probability, and the magnetic dipole transition probability. Coronal lines due to some of these ions have been observed, while others are yet to be observed. The tales for the Al I and Cl I sequences include elements up to germanium.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 46; Jan. 197
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  • 36
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    A theory of ring formation around Be stars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A theory for the formation of gaseous rings around Be stars is developed which involves the combined effect of stellar rotation and radiation pressure. A qualitative scenario of ring formation is outlined in which the envelope formed about a star from ejected material is in the form of a disk in the equatorial plane, collisions between ejected gas blobs are inevitable, and particles with high angular momenta form a rotating ring around the star. A quantitative description of this process is then formulated by considering the angular momentum and dynamical energy of the ejected matter as well as those of the ring alone, without introducing any other assumptions.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 88
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  • 37
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    Radius of the Vela pulsar (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Lasker (1976) has proposed to identify a B roughly equals 23.7 mag star as thermal radiation from the hot neutron star associated with the Vela pulsar. It is shown that this identification, if correct, together with existing X-ray surveys of the Vela supernova remnant, requires that the radius of this pulsar certainly exceed 45 km, and probably 95 km.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Aug. 15
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  • 38
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    Hectometric and kilometric solar radio emission observed from satellites in August 1972 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Type II, type III, and continuum solar radio events, as well as intense terrestrial magnetospheric radio emissions, were observed at low frequencies (10 MHz to 30 kHz) by the IMP-6 satellite during the period of high solar activity in August 1972. This review covers briefly the unique direction-finding capability of the experiment, a detailed chronology of the low-frequency radio events, and, where possible, their association with both ground-based radio observations and solar flares. The attempted observation of solar bursts in the presence of intense magnetospheric noise may, as illustrated, lead to erroneous results in the absence of directional information. The problem of assigning an electron-density scale and its influence on determining burst trajectories is reviewed. However, for the disturbed conditions existing during the period in question, it is felt that such trajectories cannot be determined accurately by this method. The capabilities, limitations, and observing programs of present and future satellite experiments are briefly discussed.
    Keywords: SOLAR PHYSICS
    Type: Space Science Reviews; 19; Oct
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  • 39
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    Diamagnetic boundary layers - A kinetic theory (1976)
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    Publication Date: 2011-08-17
    Description: A kinetic theory is presented for boundary layers associated with MHD tangential 'discontinuities' in a collisionless magnetized plasma, such as those observed in the solar wind. The theory consists of finding self-consistent solutions of Vlasov's equation and Maxwell's equation for stationary one-dimensional boundary layers separating two Maxwellian plasma states. Layers in which the current is carried by electrons are found to have a thickness of the order of a few electron gyroradii, but the drift speed of the current-carrying electrons is found to exceed the Alfven speed, and accordingly such layers are not stable. Several types of layers in which the current is carried by protons are discussed; in particular, cases are considered in which the magnetic-field intensity, direction, or both, changed across the layer. In every case, the thickness was of the order of a few proton gyroradii, and the field changed smoothly, although the characteristics depended somewhat on the boundary conditions. The drift speed was always less than the Alfven speed, consistent with stability of such structures. These results are consistent with observations of boundary layers in the solar wind near 1 AU.
    Keywords: SOLAR PHYSICS
    Type: Astrophysics and Space Science; 45; Dec. 197
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  • 40
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    The solar physics Shuttle/Spacelab program and its relationship to studies of the flare build-up (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The main phase of solar physics (including flare-buildup) research on Shuttle/Spacelab during the 1980s centers around the use of facility instruments for multiple-user, multiple flight operations. Three main facilities are being considered: a meter-class optical telescope for visible and near-UV wavelengths, an EUV/XUV/soft X-ray facility, and a hard X-ray imaging facility (including a full-sun 5-600 keV spectrometer, a nuclear gamma ray spectrometer, and an X-ray polarimeter for the 5-100 keV range). Smaller instruments designed for specific observations and other classes of instruments such as solar monitors that are not on the facility level are also being considered.
    Keywords: SOLAR PHYSICS
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  • 41
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    Absolute flux calibration for the Mg II observations near 2800 angstroms (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of the Mg II features near 2800 A, obtained with a balloon-borne ultraviolet stellar spectrometer for five stars, have been calibrated against the absolute flux measures from OAO-2 spectrometer results. Equivalent widths of the Mg II resonance doublet and their respective subordinate lines, as well as the emission intensities, were evaluated where applicable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 15
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  • 42
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    Plasma irregularities in the comet's tail (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Scintillation theory is invoked to explain fluctuations in radio intensity observed during occultation of the extragalactic radio source PKS 2025-15 by the plasma tail of comet 1973 XII on Jan. 5, 1975. Plasma irregularities and turbulence in the tail of the comet (Kohoutek 1973f) are fitted to a Gaussian spectrum and to a Kolmogorov power-law spectrum in analyzing the scintillation data. The rms fluctuation of electron density in the cometary tail is reported at 80 electrons per cu mm, the inner scale of the fluctuation at 800 km, and the largest scale of fluctuation at possibly 400,000 km. A hump in the comet power-law spectrum is noted. Use of the power spectrum of electron density fluctuations to predict the power spectrum of magnetic field fluctuations for irregularities associated with hydromagnetic turbulence is recommended.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Nov. 15
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  • 43
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    Millimeter emission lines in Orion A (1976)
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    Publication Date: 2011-08-17
    Description: During the course of a search of Orion A for signals from three large organic molecules, several millimeter-wave lines from known interstellar molecules were observed. Results are reported for observations of methanol (CH3OH), methyl cyanide (CH3CN), methyl acetylene (CH3CCH), acetaldehyde (CH3CHO) and (Si-29)O. Emission signals from two hydrogen recombination lines (H41-alpha and H42-alpha) detected from the H II region of Orion A are also reported. Negative results were obtained for several millimeter-wave transitions of ethylene oxide, acetone, and cyclopropenone.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Nov. 1
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  • 44
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    A search of the SAS-2 data for pulsed gamma-ray emission from radio pulsars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Data from the SAS-2 high-energy (above 35 MeV) gamma-ray experiment have been examined for pulsed emission from each of 75 radio pulsars which were viewed by the instrument and which have sufficiently well-defined period and period-derivative information from radio observations to allow for gamma-ray periodicity searches. When gamma-ray arrival times were converted to pulsar phase using the radio reference timing information, two pulsars, PSR 1747-46 and PSR 1818-04, showed positive effects, each with a probability of less than 1 part in 10,000 of being a random fluctuation in the data for that pulsar. These are in addition to PSR 0531+21 and PSR 0833-45, previously reported. The results of this study suggest that gamma-ray astronomy has reached the detection threshold for gamma-ray pulsars and that work in the near future should give important new information on the nature of pulsars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Oct. 15
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  • 45
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    The 1976 Helios and Pioneer solar conjunctions-continuing corroboration of the link between Doppler noise and integrated signal path electron density (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observed Doppler noise (rms phase jitter) from the 1976 solar conjunctions of the Helios 1 and 2 and the Pioneer 10 and 11 spacecraft was processed with a recently developed Doppler noise model ISEDB. Good agreement is obtained between the observed data and the model. Correlation is shown between deviations from the ISEDB model and sunspot activity, but it is insufficient to be modeled. Correlation is also shown between ISEDB model deviations for (spacecraft) signal paths on the same side of the sun.
    Keywords: SOLAR PHYSICS
    Type: The Deep Space Network; p 121-137
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  • 46
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    An interpretation of beta Lyrae. II - Disk luminosity, mass ratio, and nature of the secondary component (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Sept. 15
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  • 47
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    Interplanetary disturbances caused by the August 1972 solar flares as observed by Pioneer 9 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Pioneer 9 plasma and field observations at 0.78 AU were used as the basis of the analysis of the dynamic behavior of the interplanetary medium during early August, 1972. The following investigations were carried out: (1) energy and mass estimates for the solar flares of Aug. 2, 4, and 7; (2) shock wave characteristics; and (3) a numerical simulation of the first two flare-generated disturbances on Aug. 2, 4, and 7.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 81; Sept. 1
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  • 48
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    Structure of the extended solar magnetic field and the sunspot cycle variation in cosmic ray intensity (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: It is proposed that a relation exists between the extent of interplanetary-magnetic-field sectors and observed variations in cosmic-ray intensity at earth. Changes that take place in the sector magnetic fields and solar polar fields during a sunspot cycle are described. It is argued that a geometrical effect arising from changes in sector-field and polar-field extent during sunspot cycles may be the principal cause of the 11-yr modulation of cosmic-ray intensity observed at earth. The fraction of the heliosphere occupied by sector fields is estimated as a function of time through an average sunspot cycle, the solid angle of the heliosphere occupied by the extended solar polar fields is plotted through the same cycle, and monthly averages of observed absolute intensities of primary cosmic rays with a rigidity greater than 0.5 GV are compared with the plot of polar-field extent. It is found that the average sunspot-cycle variation of the solid angle of the extended polar fields is rather similar to the observed variation in the flux of the cosmic rays considered.
    Keywords: SOLAR PHYSICS
    Type: Nature; 262; Aug. 26
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  • 49
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    Observations of intensity and linear polarization of CTB 80 at 6 and 2.8 cm (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper presents observations of the distribution of intensity and linear polarization over the radio source CTB 80 at 6 and 2.8 cm. The physical nature of the source is examined, particularly the relation between the strong central component and a ridgelike structure that extends across the northern half in the E-W direction. The structure, nonthermal spectrum, and polarization of the central component are found to be very similar to those of a supernova remnant, but the ridge is shown to be unlike any feature of any other SNR. It is suggested that the ridge may have resulted from expansion of the remnant shell into a dense interstellar cloud or, alternatively, that CTB 80 might be a nearby extragalactic radio source similar to Centaurus A.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 51; 1, Au; Aug. 197
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  • 50
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    X-ray evidence for the supernova origin of the North Polar spur (1976)
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    Publication Date: 2011-08-16
    Description: Soft X-ray observations during four scans across the North Polar radio continuum spur have provided additional evidence that the spur encircles an old supernova remnant. From the measured intensity of the X-ray emission, and the known diameter of the remnant, it is estimated that its age is several hundred thousand years and that the supernova was of Type II, with an energy between 10 to the 51st and 10 to the 53rd ergs.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 207; Aug. 1
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  • 51
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    Coronal temperatures and temperature gradients from OSO-7 spectroheliograms (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Temperatures and temperature gradients for the outer corona are obtained from brightness gradients of EUV lines that were measured with the spectroheliograph on OSO-7. Brightness gradients show considerable deviations from isothermal model calculations that include collisional excitation and photoexcitation. A negative temperature gradient that gives both positive and negative ion-abundance gradients appears to be able to account for the discrepancy. For the 284-A of Fe XV, perhaps the strongest line from the outer corona, measurements during 1972 appear to be consistent with a temperature near 2.3 million K near the equator at about 1.3 solar radii from the solar center and with temperature-gradient values near -0.7 that extend from as low as 1.2 to about 1.8 solar radii. Temperatures from strong lines of Fe XIV and Fe XVI indicate that variations of about 200,000 K exist along lines of sight where emission is appreciable. There appears to be some agreement between these results and temperature measurements from ion abundances in the solar wind and the Doppler width of the 5303-A line.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 47; Apr. 197
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  • 52
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    Nonlinear coupling between pulsation and convection in late type stars (1976)
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    Publication Date: 2011-08-17
    Description: A simple idealized nonlinear model applicable to long-period variable stars has been formulated which assumes that the convective envelope of M giants is composed of giant convection cells comparable in size to the stellar radius. The simplicity of this model essentially constitutes a physical analog to the strong dynamic coupling that occurs if the convective envelope of the star undergoes both modes of motion. As shown implicitly in the time scales associated with these motions, the coupling produces asymmetrical fluctuations of the entire star, the mean velocity of which is comparable to the escape velocity of the star at particular values of the ratio of the pulsation and convection time scales. It is suggested that this can account for the mass loss from late-type stars and the circumstellar dust shells that are associated extensively with long-period variables. For critical values of the pulsation and convection time scales, the solutions correspond to the rapid expansion of the entire convective envelope and are the basis of a mechanism that simulates the manner in which pulsating stars ballistically accelerate their convective shells to form planetary nebulae.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science; 45; Nov. 197
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  • 53
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    Limb-brightening observations from the OSO-7 satellite. II - Comparison of Abel-inverted intensities of Fe XIV and Fe XIII EUV emission lines with predictions (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Intensities of Fe XIV and Fe XIII EUV emission lines obtained at coronal locations beyond the limb by the Goddard spectroheliograph on the OSO 7 satellite have been corrected for the wavelength dependence of the instrument's sensitivity and have been Abel-inverted to provide a valid comparison with theoretical predictions for each ion. Details of the Abel-inversion procedure are given, including explicit formulas for application of Bracewell's (1956) method. The intensity ratios of pairs of lines originating from a common level are compared with expected theoretical transition probability ratios over a range of heliocentric distance; deviations in some cases yield information about adjacent unclassified lines. Comparison of the observations with predictions for Fe XIV and Fe XIII shows generally good agreement, with a few interesting discrepancies that may imply a corresponding need for more accurate collisional excitation cross sections. The same comparison yields the variation of electron density with heliocentric radius for each ion separately; the two density functions are found to agree within a factor of three.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics; 53; 2, De; Dec. 197
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  • 54
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    Scalar-tensor theory of gravitation with negative coupling constant (1976)
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    Publication Date: 2011-08-17
    Description: The possibility of a Brans-Dicke scalar-tensor gravitation theory with a negative coupling constant is considered. The admissibility of a negative-coupling theory is investigated, and a simplified cosmological solution is obtained which allows a negative derivative of the gravitation constant. It is concluded that a Brans-Dicke theory with a negative coupling constant can be a viable alternative to general relativity and that a large negative value for the coupling constant seems to bring the original scalar-tensor theory into close agreement with perihelion-precession results in view of recent observations of small solar oblateness.
    Keywords: ASTROPHYSICS
    Type: Nuovo Cimento; vol. 35
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  • 55
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    Theoretical models of Beta Cephei stars constructed with new radiative opacities (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Equilibrium models for the main-sequence and early post-main-sequence phases of evolution are constructed for stars of 10.9 and 15 solar masses with two different initial hydrogen and metals abundances. Carson's (1976) radiative opacities are used in the calculations. It is found that the models which lie off the zero-age main sequence have cooler effective temperatures than corresponding models based on other opacities and cross the observed Beta Cephei strip in the H-R diagram only during the main phase of core hydrogen burning. The stability of radial and nonradial pulsations is studied by applying linear nonadiabatic perturbations to the models. The results show that all the modes examined are stable and that the margin of stability decreases with advancing evolution. It is suggested that the closeness of the periods of the two lowest nonradial quadrupole p-modes may be responsible for the 'beat' phenomenon observed in many Beta Cephei stars, if these modes are somehow excited. Possible instability mechanisms are evaluated, particularly the ultimate ionization of CNO elements.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 1
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  • 56
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    Radioactivity in the galactic plane (1976)
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    Publication Date: 2011-08-17
    Description: The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.
    Keywords: ASTROPHYSICS
    Type: Nature; 264; Nov. 4
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  • 57
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    Pulsar average wave forms and hollow-cone beam models (1976)
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    Publication Date: 2011-08-17
    Description: Pulsar wave forms have been analyzed from observations conducted over a wide radio-frequency range to assess the wave-form morphologies and to measure wave-form widths. The results of the analysis compare favorably with the predictions of a model with a hollow-cone beam of fixed dimensions and with random orientation of both the observer and the cone axis with respect to the pulsar spin axis. A class of three-component wave forms is included in the model by adding a central pencil beam to the hollow-cone hypothesis. The consequences of a number of discrepancies between observations and quantitative predictions of the model are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Nov. 1
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  • 58
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    Pulsating X-ray sources - Slowly rotating neutron stars (1976)
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    Publication Date: 2011-08-17
    Description: The origin of the slowly pulsating X-ray sources is considered. It is shown that tidal forces in a presupernova binary system will lead to synchronization of the stellar rotation with the orbital period. Consideration of the structure of the presupernova star then indicates that X-ray periods of the correct order of magnitude will be produced in these systems.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Oct. 15
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  • 59
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    The astrometric binary Mu Cassiopeiae - Photographically almost resolved (1976)
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    Publication Date: 2011-08-17
    Description: Photographic observations of the Population II subdwarf astrometric binary Mu Cas are described which almost resolve the components and permit an estimate of their magnitudes and separation. Red- and blue-light photographs of the system were taken during an observing period when the component separation was maximum. The separation of the two components is estimated to be about 1.5 arcsec, position angles of about 194 and 201 deg are determined for the two years of the observing period, and the apparent magnitude of the faint companion is found to be approximately 10.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Oct. 15
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  • 60
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    SAS-2 gamma-ray observations of PSR 1747-46 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Evidence is reported for the observation of gamma-ray emission from the radio pulsar PSR 1747-46 by the gamma-ray telescope aboard SAS 2. The evidence is based on the presence of both an approximately 3-sigma enhancement of gamma rays at the pulsar's location and an approximately 4-sigma peak in the phase plot of 79 gamma-ray events whose phase was calculated from the pulsar's known period. The gamma-ray pulsation is found to appear at a phase lag of about 0.16 from that predicted by the radio observations. The pulsed gamma-ray fluxes above 35 MeV and 100 MeV are estimated, and it is shown that the gamma-ray pulse width is similar to the radio pulse width. It is concluded that PSR 1747-46 is a most likely candidate for pulsed gamma-ray emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 17; 4, 19; 1976
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  • 61
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    On the theory of the type III burst exciter (1976)
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    Publication Date: 2011-08-17
    Description: In situ satellite observations of type III burst exciters at 1 AU show that the beam does not evolve into a plateau in velocity space, contrary to the prediction of quasilinear theory. The observations can be explained by a theory that includes mode coupling effects due to excitation of the parametric oscillating two-stream instability and its saturation by anomalous resistivity. The time evolution of the beam velocity distribution is included in the analysis.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 46; Feb. 197
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  • 62
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    Directivity of low frequency solar type III radio bursts (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The occurrence rate of type III solar bursts in the frequency range 4.9 MHz to 30 kHz is analyzed as a function of burst intensity and burst arrival direction. We find that (1) the occurrence rate of bursts varies inversely with the 1.5 power of the flux, and (2) the distribution of burst arrival directions at each frequency shows a significantly larger number of bursts observed west of the earth-sun line than east of it. This western excess in occurrence rate appears to be correlated with the direction of the average interplanetary magnetic field, and is interpreted as beaming of the observed burst radiation along the magnetic field direction.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 46; Feb. 197
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    The 35-d X-ray profile of Her X-1 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Results of an analysis of more than 500 days of Ariel 5 All-Sky Monitor data are reported which support the view that enhanced X-ray emission from Her X-1 occurs regularly in the source's 35-day cycle. The data analyzed show that the enhancement is centered at phase 0.55 (+ or - 0.05) relative to the maximum, has an intensity of at least one-fourth of the maximum, and has an apparent duration not exceeding 10% of the 35-day cycle. It is strongly suggested that the enhancement occurs in every cycle at about one-third of the maximum.
    Keywords: ASTROPHYSICS
    Type: Nature; 263; Oct. 7
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  • 64
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    Results from the Ariel 5 All-Sky Monitor (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Results are summarized for the first year of operation of the Ariel 5 All-Sky Monitor. The monitor is described in detail, and representative observations of the transient sources A1524-62, Cen X-mas, A0535+26, and A0620-00 are discussed. It is shown that the transients are largely confined to the galactic plane and that about 100 such sources per year can be expected in the Galaxy. Long-term observations of Sco X-1, Cyg X-3, and Cyg X-1 are reported which illustrate that the large intensity variations in Sco X-1 appear to correlate on time scales greater than one Ariel 5 orbit, that Cyg X-3 has a widely varying intensity, and that the predominant feature of the intensity variation in Cyg X-1 is a minimum near superior conjunction.
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  • 65
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    The quiet sun chromospheric network observed from Skylab (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper analyzes spectra of a supergranulation cell interior and cell boundary obtained near the solar center at wavelengths between 1200 and 1560 A with a normal-incidence spectrograph aboard Skylab. Absolute intensities, relative intensities, and profiles are given for selected optically thin and optically thick lines over the cell interior, the boundary, and intermediate positions; the results are compared with spectra obtained at the limb. Characteristic lengths along the line of sight are derived for the Si III emitting region, and these are compared with the predictions of Gabriel's (1975) model. It is concluded that the present data are representative of a fairly typical cell interior and boundary, that nonthermal motions are isotropic and the same for the interior and boundary, and that the electron-density ratio between the interior and the boundary is about a factor of two or less.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; 209; Oct. 1
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  • 66
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    Gravitational collapse of a turbulent vortex with application to star formation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The gravitational collapse of a rotating cloud or vortex is analyzed by expanding the dependent variables in the equations of motion in two-dimensional Taylor series in the space variables. It is shown that the gravitational and rotational terms in the equations are of first order in the space variables, the pressure-gradient terms are of second order, and the turbulent-viscosity term is of third order. The presence of turbulent viscosity ensures that the initial rotation is solid-body-like near the origin. The effect of pressure on the collapse process is found to depend on the shape of the initial density disturbance at the origin. Dimensionless collapse times, as well as the evolution of density and velocity, are calculated by solving numerically the system of nonlinear ordinary differential equations resulting from the series expansions. The axial flow is always inward and allows collapse to occur (axially) even when the rotation is large. An approximate solution of the governing partial differential equations is also given in order to study the spatial distributions of the density and velocity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Oct. 1
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  • 67
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    The origin of OB associations and extended regions of high-energy activity in the Galaxy through supernova cascade processes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A number of observed characteristics of OB associations, including their positive total energies and subgroup structure, are explained by the hypothesis that an association is composed of stars formed by compression of interstellar clouds in blast waves of several generations of supernovae. The later-generation supernovae are simply the most massive stars formed by this mechanism in the earlier generations. This supernova cascade process may also be responsible for giant loops such as the North Polar Spur. Enhanced high-energy gamma-ray emission is expected from the loops.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 209; Oct. 1
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  • 68
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    Cloud acceleration by cosmic rays in the vicinity of compact luminous objects (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Nonrelativistic cosmic rays from a central source exert an outward pressure on the surrounding gas in a Seyfert nucleus or the envelope of a quasi-stellar object. This force is different from radiation pressure in that the momentum transfer to the gas is enhanced rather than reduced when the gas is ionized. Calculations are presented to show that particle energy flux comparable to observed photon luminosities will accelerate gas clouds as large as 100,000 solar masses to velocities on the order of 0.1c in the presence of a central mass of 100 million solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Sept. 15
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  • 69
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    An X-ray redshift measure for clusters of galaxies up to z not less than 1 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Correlated measurements of redshifted iron line emission and apparent surface brightness are suggested for unambiguously defining intrinsic X-ray characteristics for clusters of galaxies up to z not less than 1. If some of the weak unidentified high-galactic-latitude X-ray sources are clusters at z roughly equal to 1-3, then such correlated measurements should be feasible within the complement of instruments aboard the HEAO-B orbiting X-ray telescope observatory. In addition, those clusters at z less than 1 would require spectral data from broader bandwidth experiments, such as the all-sky survey to be provided by the proportional counters aboard the first mission of the High Energy Astronomy Observatory (HEAO-A).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Aug. 15
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  • 70
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    Search for X-ray emission from globular clusters using Uhuru data (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Aug. 15
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  • 71
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    An improved radiation metric (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An improved radiation metric is obtained in which light rays make a small nonzero angle with the radius, thus representing a source of finite size. Kaufmann's previous solution is criticized. The stabilization of a scatterer near a source of gravitational field and radiation is slightly enhanced for sources of finite size.
    Keywords: ASTROPHYSICS
    Type: General Relativity and Gravitation; 7; 2, 19; 1976
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  • 72
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    Two UV colours of the central part of M 31 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Two photographs of the galaxy M 31 have been obtained in the far UV with a Faust rocket experiment and in the near UV with the S 183 experiment aboard Skylab. Only the central part of the galaxy is detected. Reductions provide both the energy received and the angular area over M 31 from which it is emitted. The UV flux is brighter than expected from extrapolation of the visible spectrum. The distribution below 300 A is rather flat and different from previous OAO-2 observations. These results, combined with Lyman continuum flux evaluation, are used to discuss the temperature and the age of the stars which may be responsible for this anomalous UV distribution.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 50; 3, Au; Aug. 197
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  • 73
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    Competition of neutrino and gravitational radiation in neutron star formation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An investigation is conducted concerning the possibility that neutrino radiation rather than gravitational radiation may be the dominant way by which nonradial pulsations are damped out in a collapsing star. The effects of neutrino radiation on the nonradial oscillations of such objects are examined and damping times corresponding to a particular neutrino production mechanism are evaluated. The obtained results imply that neutrino radiation, by more rapid damping of the nonradial oscillations of a newly formed neutron star in a supernova explosion, would hinder gravitational radiation, thus reducing the possibility of its detection.
    Keywords: ASTROPHYSICS
    Type: Nature; 262; Aug. 19
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  • 74
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    ALSEP: Quasar differential VLBI (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A program of Apollo Lunar Surface Experiments Package (ALSEP)-Quasar Very Long Baseline Interferometry (VLBI) is being reported. These observations primarily employ a 4 antenna technique, whereby simultaneous observations with two antennas at each end of an intercontinental baseline are used to derive the differential interferometric phase between a compact extragalactic radio source (usually a quasar) and a number of ALSEP transmitters on the lunar surface. A continous ALSEP-quasar differential phase history over a few hour period leads to extremely high angular accuracy in measuring the lunar position against the quasar reference frame. This application of the 4 antenna technique has been underway for more than a year and is now producing high quality data utilizing Deep Space Network (DSN) stations in Australia, Spain, and Goldstone, California, as well as the Spaceflight Tracking and Data Network (STDN) Apollo station at Goldstone.
    Keywords: ASTROPHYSICS
    Type: The Deep Space Network; p 37-54
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  • 75
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    Spectral variability in the X-ray pulsar GX 1 + 4 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Observations of the galactic-center-region hard X-ray source GX 1 + 4 by the GSFC X-ray spectroscopy experiment on OSO-8 confirm that GX 1 + 4 is a slow X-ray pulsar. The amount of absorption by cold matter in the spectrum of GX 1 + 4 varies significantly within a 24-hour period, which is typical of many X-ray binary systems. The light curve for the pulsations from GX 1 + 4 appears to be energy-dependent.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 207; Aug. 1
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  • 76
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    Doppler wavelength shifts of transition zone lines measured in Skylab solar spectra (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Wavelengths of lines of the transition-zone ions Si IV, C IV, O IV, N V, and O V are observed to be redshifted relative to the wavelengths of chromospheric lines in XUV spectra obtained from the normal-incidence spectrograph on Skylab. The spectra cover the wavelength range from 1200 to 1565 A and were obtained with the slit positioned over chromospheric network and cell regions, on coronal holes, and above the limb. The network-area and coronal-hole spectra were obtained near the disk center. Only some of the spectra show redshifted transition-zone lines. The observed shifts are between 0.03 and 0.08 A, implying velocities of 15 km/s or less. The amount of wavelength shift does not always appear to be the same for lines of different ions. The shifts imply that descending plasma in the solar atmosphere produces more emission than ascending plasma at temperatures between approximately 70,000 and 200,000 K.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; 205; May 1
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  • 77
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    Inhomogeneities in the early universe (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper investigates certain nonlinear processes that are viable candidates for the mechanisms which produced large-scale inhomogeneities in the early Universe. Several nonlinear Lagrangians are presented for matter, the Korteweg-de Vries equation is analyzed, and the existence of solitons among its solutions is noted. A model based on the possibility of generating a cascade of solitons from an initial perturbation is proposed, and it is shown how large-scale inhomogeneities can be generated when an initial soliton fragments into many others through the nonlinear action of the terms in the Korteweg-de Vries equation. A second model is examined which is based on the interaction of matter with a strong radiation field (an almost monochromatic photon gas) and which involves changes in the refractive index of the vacuum. It is found that matter and radiation will not mix if the radiation field has a nonuniform intensity and that the matter will separate into dense portions or 'cosmological protogalaxies'. The evolution of these portions of matter is studied, and it is found that conditions would be appropriate for the interface between them and the surrounding radiation field to become unstable, giving rise to a turbulent layer.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; May 1
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  • 78
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    Long-term X-ray studies of Scorpius X-1. II - Evidence for flare-dominated intensity variations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Data on Sco X-1 obtained with the Ariel-5 All-Sky Monitor are analyzed for variability, and it is found that a large fraction of the X-ray emission at 3 to 6 keV can be represented by shot noise. The results indicate that almost all the emission in this range can be sensibly associated with a multiplicity of shotlike flares (about 200 a day), each having a duration of about 0.33 day. It is concluded that the overall consistency with a multiplicity of long-duration shots (rather than single flares superposed on a baseline continuum) may be generally characteristic of sources with an accretion disk.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 15
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  • 79
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    The emission-line spectrum above the limb of the quiet sun - 1175-1940 A (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Spectra of a quiet solar region obtained at positions within and above the solar white-light limb in the wavelength region from 1175 to 1940 A are discussed. The spectra were obtained by the slit spectrograph (SO82-B) on Skylab. The spectral resolution is 0.06 A, and the projected slit area on the sun was 2 x 60 arcsec (1450 x 43500 km). Relative line intensities are presented for lines formed in the temperature region of the solar atmosphere from about 8000 to 220,000 K. Representative line profiles of both optically thin and optically thick lines are shown as a function of height above the limb. Random mass-motion velocities are deduced from the optically thin lines, and the relative intensities and profiles of the lines are discussed in terms of current theoretical models. A wavelength list with identifications is given for the spectrum obtained at +4 arcsec above the white-light limb.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series; 31; July 197
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  • 80
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    A return to the pre-1971 intensity level and a 5.6-d modulation for Cyg X-1 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A 5-day modulation in the 'high-state' X-ray intensity data obtained by the Ariel V all-sky monitor for November 1975-January 1976 is reported. The light curve decrement (the fraction of the total source emission over one 5-day cycle which is deficient at superior conjunction) is 0.019 plus or minus 0.003, compared with 0.029 plus or minus 0.004 for a similar 5.6-day modulation observed before the April 1975 flare. The results are most easily explained by scattering from ionized material between the two stellar components which extends outside the orbital plane.
    Keywords: ASTROPHYSICS
    Type: Nature; 261; May 20
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  • 81
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    Magnetic monopoles and cosmology (1976)
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    Publication Date: 2011-08-16
    Description: The number density of magnetic monopoles is calculated in the framework of big-bang cosmology on the basis of a solution to the Boltzmann transport equation in evolutionary cosmological models. The product of the mass and the transition probability of the annihilation process for magnetic monopoles is obtained relative to those for protons and is shown to be greater than about 10 to the 20th power. Based on this result, two likely conclusions are made: (1) monopoles exist, but possess a pole-antipole bound state with binding energy of the order of the monopole rest mass; or (2) magnetic monopoles do not exist.
    Keywords: ASTROPHYSICS
    Type: Physics Letters; 61B; Apr. 12
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  • 82
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    Excitation of pulsations in the CNO ionization zone of luminous stars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Homogeneous models of luminous hydrogen-and-helium burning stars were constructed on the basis of Carson's new radiative opacities. These opacities exhibit a large 'bump' at moderate temperatures and low densities as a result of the ultimate ionization of the CNO group of elements and they induce in the envelopes of the more massive stars a strong local convection zone, a high central condensation and pulsational instability by means of the kappa-mechanism above a certain stellar mass. This critical mass for Population I hydrogen-burning stars is probably greater than 45 solar masses for the fundamental radial mode, with the overtones being more stable, while for the homogeneous helium-burning stars, the critical mass lies in the range 2-6 solar masses for all modes up to at least the third overtone. Convection is alternately treated by means of the mixing length theory and the assumption of strict adiabaticity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 83
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    Solar irradiance - Total and spectral and its possible variations (1976)
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    Publication Date: 2011-08-16
    Description: The present status of our knowledge of the total and spectral irradiance of the sun is briefly reviewed. The currently accepted NASA/ASTM standard values of the solar constant and the extraterrestrial solar spectral irradiance are presented. The uncertainties in these values are relatively high. Data on the variability of the solar constant are conflicting and inconclusive. The variability of solar spectral irradiance is almost totally unknown and unexplored. Some alleged sun-weather relationships are cited in support of the need to know more precisely the variations in total and spectral solar irradiance. An overview of the solar monitoring program of NASA is presented, with special emphasis on the Solar Energy Monitor in Space (SEMIS) experiment which has been proposed for several spacecraft missions. The monitor is a combination of a solar-constant detector and a prism monochromator.
    Keywords: SOLAR PHYSICS
    Type: Applied Optics; 15; Apr. 197
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  • 84
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    Ultraviolet observations of cool stars. V - The local density of interstellar matter (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A high-resolution Copernicus observation of the chromospheric Ly-alpha emission line of the nearby (3.3 pc) K dwarf epsilon Eri sets limits on the velocity, the velocity dispersion, and the density of atomic hydrogen in the local interstellar medium. Analysis shows that the interstellar Ly-alpha absorption is on the flat portion of the curve of growth. An upper limit of 0.12 per cu cm is derived for the atomic-hydrogen density. The value of this density is 0.08 (plus or minus 0.04 per cu cm if the velocity-dispersion parameter is 9 km/s, corresponding to a temperature of 5000 K. Also, the interstellar deuterium Ly-alpha line may be present in the spectrum.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 1
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  • 85
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    Suppression of bar instability by a massive halo (1976)
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    Publication Date: 2011-08-16
    Description: Numerical experiments are performed to determine the effect of a spherical uniform-density mass distribution or halo on the evolution of stellar disks. For a halo with radius much smaller than that of the disk, the large-scale bar-forming instability is prevented by a fixed halo (or core) component containing 60% of the total system mass. Similar results are obtained for a halo component corresponding to the Schmidt (1965) model of the Galaxy. For a uniform-density spherical halo with radius equal to that of the stellar disk, a halo component containing only 40% of the total mass is sufficient to stabilize the bar-forming mode. These results indicate that a large halo is more effective in stabilizing against bar formation than a more centrally condensed core-halo.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 81; Jan. 197
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  • 86
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    Isotopic abundances of Hg in mercury stars inferred from the Hg II line at 3984 A (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Wavelengths of the Hg II absorption feature at 3984 A in 30 Hg stars are distributed uniformly from the value for the terrestrial mix to a value that corresponds to nearly pure Hg-204. The wavelengths are correlated loosely with effective temperatures inferred from Q(UBV). Relative isotopic abundances derived from partially resolved profiles of the 3984-A line in iota CrB, chi Lup, and HR 4072 suggest that mass-dependent fractionation has occurred in all three stars. It is supposed that such fractionation occurs in all Hg stars, and a scheme whereby isotopic compositions can be inferred from a comparison of stellar wavelengths and equivalent widths with those calculated for a family of fractionated isotopic mixes. Theoretical profiles calculated for the derived isotopic composition agree well with high-resolution interferometric profiles obtained for three of the stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 87
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    Stellar evolution at high mass with semiconvective mixing according to the Schwarzschild criterion (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Evolutionary sequences for stellar models with 10, 15, 30, and 60 solar masses, as well as four different initial chemical compositions, are calculated to the end of core helium burning using the Schwarzschild criterion for convection. The results are analyzed in terms of the modifications of interior structure and surface parameters induced by semiconvective mixing as a result of adopting the Schwarzschild criterion. It is found that the main differences from results based on the Ledoux criterion are the great extent of the convectively unstable layers in the intermediate zone and the eventual development of a fully convective zone at the base of the semiconvective one. It is shown that semiconvection develops outside the convective core just after the ZAMS stage for masses greater than 12 solar masses and just before the stage of central hydrogen exhaustion for masses greater than 6 solar masses. The present models are found to be insufficiently hot in comparison with the bulk of observed stable blue supergiants and to predict far too many red supergiants fro the range above 20 solar masses. It is concluded that something is fundamentally wrong with the models, the most likely suspects being the stellar opacities adopted and the neglect of mass loss.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 1
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  • 88
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    Solar gamma-ray lines as probes of accelerated particle directionalities in flares (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Anisotropies of charged particles accelerated in solar flares can be studied by observing Doppler shifts of selected gamma-ray lines. The spectral shape of the 6.1-MeV line of O-16 is calculated. If the accelerated particles are isotropic, the line remains centered at an emitting-nucleus rest-frame energy of 6129.4 keV, and its width (FWHM) is about 100 keV. However, for particle anisotropies that may be produced in solar flares, the line is shifted to lower energies by about 30 to 40 keV.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; 203; Feb. 1
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  • 89
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    Limit on the secular change of the gravitational constant based on studies of solar evolution (1976)
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    Publication Date: 2011-08-16
    Description: The past and present observable properties of the sun have been theoretically calculated on the assumption that the gravitational constant G increases or decreases with time. Consideration of Davis's experimental upper limit on the present solar neutrino flux and of terrestrial paleontological data sets a limit on the absolute rate of change of G, namely, the absolute value of the quotient of the change in the gravitational constant and the gravitational constant is less than 1/10 billion/yr, if other standard constants do not also change with time.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 36; Apr. 12
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  • 90
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    Evidence for a 17-d periodicity from Cyg X-3 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Data are presented from the Ariel-V All-Sky Monitor which indicate a 17-day periodicity of the X-ray spectra from Cyg X-3 (3U2030+40). The data are consistent with data from the Ariel V Sky Survey Experiment. Assuming that the high intensity state of Cyg X-3 is well fitted by a structureless black body (Serlemitsos et al., 1975), and that the 17-day maxima correspond to increased electron scattering in the source, it is suggested that the 17-day effect is analogous to the 35-day variation in Her X-1. The possible explanation of this phenomenon as a result of the 17-day orbital period of the binary system containing Cyg X-3 is severely constrained by the stability of the well-known 4.8-hour variation.
    Keywords: ASTROPHYSICS
    Type: Nature; 260; Apr. 15
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  • 91
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    New galactic population class (1976)
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    Publication Date: 2011-08-16
    Description: It has been found that galactic gamma rays come from regions in which molecular hydrogen is dense and in which 'population I' objects are predominantly found. An interpretation of the existence of such regions leads to a proposal for a change in the Baade classification scheme. 'Population I' is to include all the objects associated with the H2 clouds. A new class, 'population 0' is to refer to the regions, relatively richer in atomic hydrogen, which lie further from the galactic center.
    Keywords: ASTROPHYSICS
    Type: Nature; 260; Apr. 1
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  • 92
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    Evolutionary problems of Cepheids and other giants investigated with new radiative opacities (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Comparison of evolutionary tracks, pulsation constants, and linearized pulsational-stability coefficients for stellar models applicable to the problems of classical Cepheids, whose structures were calculated using the Cox-Stewart (1965) opacities and a recently computed set of opacities. The latter are based on the hot 'Thomas-Fermi' statistical model of the atom for all elements heavier than hydrogen and helium; they contain larger helium and metals contributions, but a smaller hydrogen contribution than the former ones for the same chemical composition. The difference in metals contribution affects mainly the location and shape of the evolutionary tracks on the H-R diagram, while the difference in hydrogen and helium contributions has its greatest effect on the pulsational properties of the Cepheid models. From the comparison of evolutionary tracks it is concluded that: (1) the theoretical M/L relation for evolved giants is changed very little by using the second set of opacities; (2) Q-values for the fundamental mode of radial pulsation in Cepheid envelope models increase if the second set is used, but the classical mass discrepancy remains; and (3) the second set leads to pulsational-instability.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 1
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  • 93
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    Infrared observations of ices and silicates in molecular clouds (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Spectrophotometric observations from 2 to 4 microns and from 8 to 13 microns of several infrared sources associated with molecular clouds are reported. Narrow absorption features at 3.08 microns, attributed to interstellar ices, appear in all sources with a molecular cloud in the intervening line of sight. All sources showing ice absorptions also show broad absorption features, attributed to cold silicates, from 8 to 13 microns. The observed ice absorption profiles are all quite similar; however, they do not fit in detail Mie theory predictions of extinction for pure H2O or NH3 ices. The ratio of ice-to-silicate optical depths is found to vary, with most sources showing a ratio in the range 0.1-0.4. The ratio of visual extinction to ice absorption is found to increase rapidly from inside to outside the molecular cloud in NGC 2024.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 207; Aug. 1
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  • 94
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    The emission-line spectrum above the limb of a solar coronal hole - 1175-1940 A (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Emission-line spectra of a coronal hole that coincided with the north pole of the sun are discussed which were obtained with a slit spectrograph aboard Skylab at positions within and above the solar white-light limb in the wavelength range from 1175 to 1940 A. Relative line intensities, line profiles, and full widths at half-maximum are presented for selected chromospheric and transition-zone lines observed above the present polar coronal hole. Average mass motions in the transition zone are determined as a function of electron temperature from the widths of the optically thin lines by assuming ionization equilibrium. The line intensities and profiles are compared with corresponding results deduced from spectra obtained above a quiet solar region. The coronal-hole spectra are found to imply an angular dependence for the source function as well as a radial dependence such that the source function is the smallest at the south pole and increases with decreasing solar latitude.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal Supplement Series; 31; July 197
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  • 95
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    Electron parameter correlations in high-speed streams and heat flux instabilities (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Statistical electron parameter correlations associated with high-speed streams are determined with the aim of identifying one or more locally active solar wind heat flux instabilities. Evidence that points toward local regulation of the heat flux at 1 AU is presented, and the results of a search for special signatures expected from the action of the Alfven, magnetosonic, and whistler flux instabilities are discussed. It is shown that under certain conditions, the whistler mode can be active in regulating the heat flux at 1 AU.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 81; May 1
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  • 96
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    Cometary capture missions: Benefits for habitation and materials processing on the lunar surface (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Keywords: ASTROPHYSICS
    Type: Lunar Science Inst., Abstracts of Papers Presented at a Special Session of the Seventh Annual Lunar Science Conference on Utilization of Lunar Materials and Expertise for Large Scale Operations in Space; p 148-149
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  • 97
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    The dynamical interaction between galaxies and intracluster gas in clusters of galaxies (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The interaction between the hot gas inferred to exist in clusters of galaxies and the interstellar medium of a spherical galaxy has been studied by means of time-dependent numerical hydrodynamics. Galaxies moving at transonic speeds with respect to the ambient medium lose 80% to 90% of their interstellar gas before a crossing time has elapsed. The amount of gas remaining is consistent with current observational limits to the gas content of elliptical galaxies. Negligible heating of the intracluster gas results from this process. Implications of these results for spiral galaxies with halos, radio sources in clusters of galaxies, and globular clusters in galactic halos are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 15
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  • 98
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    Radiative transfer in circumstellar dust shells (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An iterative numerical procedure is developed to calculate the radiation field as a function of position, direction, and wavelength within a spherically symmetric circumstellar dust shell. The dust shell is assumed to consist of gray, isotropically scattering dust particles in thermal equilibrium with the radiation field and to be characterized by seven parameters: radius of the central star, inner radius of the shell, outer radius of the shell, total optical depth of the shell, an index which specifies the density distribution, albedo of the dust particles, and temperature of the central star. When the shell is close to the star, the angular distribution of the stellar component of the radiation field is determined by direct integration along lines of sight to the stellar surface, and the back-warming effect of the shell is included in the calculations to determine the net stellar flux. Using this procedure, the temperature distributions and radiation fields within several model dust shells are determined and used to calculate for each shell the spectral-energy and spatial-energy distributions of the radiation emitted at 11 wavelengths from 0.4 to 20 microns. For shells of moderate optical depth, it is found that the radiation field is quite anisotropic, especially at shorter wavelengths, and that the shape of the spectral-energy distribution is strongly dependent on all seven model parameters. The Eddington factor as a function of wavelength and optical depth is calculated for each model.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 15
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  • 99
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    The evolution of rotating stars. I - Method and exploratory calculations for a 7-solar-mass star (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A method is developed which allows the evolution of rotating stars to be studied well beyond the main-sequence stage. Four different cases of redistribution of angular momentum in an evolving star are considered. Evolutionary sequences for a 7-solar-mass star, rotating according to these different cases, were computed from the zero-age main-sequence to the double-shell-source stage. Each sequence was begun with a (typical) equatorial rotational velocity of 210 km/s. On the main sequence, the effects of rotation are of minor importance. However, as the core contracts during later stages, important effects arise in all physically plausible cases. The outer regions of the cores approach critical velocities and develop unstable angular-velocity distributions. The effects of these instabilities should significantly alter the subsequent evolution.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Nov. 15
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  • 100
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    Observational constraints on the masses of neutron stars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The present state of empirical knowledge about neutron-star masses is reviewed. It is shown how the mass function of a pulsar-containing binary system can be inferred from measurements of the pulsation period and the projected semimajor axis of the pulsar orbit plus independent information concerning the inclination of the orbital plane, the mass of the companion star, or both. Relevant observational properties, the type of information used to constrain the pulsar mass, and the range of allowable pulsar masses are summarized for the binary systems 3U 0900-40, Cen X-3, SMC X-1, Her X-1, and PSR 1913+16. It is found that as long as the general theory of relativity is correct, neutron-star masses should range from about 1.4 to 1.9 solar masses if the companion is a normal white dwarf or should be less than about 1.9 solar masses if the companion is some other object. It is concluded that these mass estimates are entirely consistent with the predictions of nuclear physics theory.
    Keywords: ASTROPHYSICS
    Type: Nature; 264; Nov. 18
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