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  • Chemical Engineering  (796)
  • ASTRONOMY  (597)
  • 1980-1984  (844)
  • 1975-1979  (549)
  • 1925-1929
  • 1981  (844)
  • 1977  (549)
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  • 1980-1984  (844)
  • 1975-1979  (549)
  • 1925-1929
Year
  • 1
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    Toward diffraction-limited seeing of dim astronomical objects from the Earth's surface using LIDAR (1977)
    In:  CASI
    Details
    Publication Date: 2005-02-28
    Keywords: ASTRONOMY
    Type: Res. in the Space Sci., Vol. 2, No. 1; 12 p
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  • 2
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    Infrared astronomy and high energy astrophysics (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    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, yield information about the total mass of molecular clouds, the large-scale structure of the inner galaxy, and the density of cosmic rays.
    Keywords: ASTRONOMY
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 203-214
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  • 3
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    Spectroscopy in X-ray astronomy (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: Detailed features in cosmic X-ray sources and their associated temporal variation over a wide energy range were studied. Excess emission and absorption at approximately 6 to 7 kiloelectron volts in the spectra of supernova remnants, binary X-ray sources, and clusters of galaxies were observed. A gas scintillation proportional counter (GSPC) will be used as the detector system. In the gas scintillator the principal limitation is due to the statistics of the initial ionization process only.
    Keywords: ASTRONOMY
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 4
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    Far ultraviolet astronomy using the FAUST telescope (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: The Far Ultraviolet Space Telescope (FAUST) a compact, wide field-of-view, far ultraviolet instrument designed for astronomical observations of extended and point sources is discussed. The design and application of the instrument are described. The prime objective is to observe faint astronomical sources with sensitivities higher than previously available. Scientific programs will include: (1) a search for ultraviolet stars which are predicted to exist at the stage of evolution prior to the final death of a star; (2) observations of galaxies and quasars; and (3) joint programs with other Spacelab 1 experiments. The secondary objective is to verify the suitability of the Spacelab as a platform for far ultraviolet astronomy: data will be provided on the ultraviolet background levels due to astronomical, terrestrial, and spacecraft generated sources; the levels of contaminants which affect ultraviolet instruments; and the capability of the Orbiter for stable pointing at celestial sources for useful periods of time.
    Keywords: ASTRONOMY
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 5
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    Stabilization of Kepler's problem (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A regularization of Kepler's problem due to Moser (1970) is used to stabilize the equations of motion. In other words, a particular solution of Kepler's problem is imbedded in a Liapunov stable system. Perturbations can be introduced into the stabilized equations.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 16; Sept
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  • 6
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    Aperture averaging effects in stellar scintillation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Stellar scintillation has been measured for apertures as low as 0.012 m by using photoncounting techniques. The scintillation measurements have been made for various aperture sizes in quick succession in order to determine experimentally the effects of aperture averaging. The results of the experiment are compared with the predictions of a model proposed earlier in the literature to quantify the phenomenon.
    Keywords: ASTRONOMY
    Type: Optics Communications; 22; Sept
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  • 7
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    Far-infrared scans of the Galactic plane (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for balloon-borne scans of the Galactic plane between longitudes of 348 and 32.5 deg, which were made in two broad spectral bands from 60 to 300 microns and from 150 to 300 microns. These results indicate that there are many bright H II regions embedded in a diffuse underlying band of emission in the examined longitude range, that the color temperatures range from 30 to 90 K, and that the width of the plane is at least 2 deg of arc in both spectral bands. A lower-limit IR luminosity of the order of 1 billion suns is computed for both the bright complex of sources at the nucleus and the underlying diffuse emission out to about + or -15 deg of arc from the nucleus. The strong relationship between far-IR emission and radio continuum expected for discrete sources is illustrated, and the results are compared with those of previous studies. It is concluded that the total far-IR luminosity of the central part of the Galaxy is understandable solely in terms of known distributions of stars and dust.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 214
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  • 8
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    90-GHz flux-density measurements of variable radio sources (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Results are presented for measurements of the flux densities of 10 variable extragalactic sources at 85.2 or 90 GHz, which were made over a period of almost seven years with the NRAO 36-ft millimeter-wave antenna. The primary flux-density calibration standards used include Jupiter, Saturn, Mars, and the small-diameter Galactic source DR 21. Measured flux densities are given as a function of time (in years) for the sources 3C 84, NRAO 150, 3C 120, OJ 287, 4C 39.25, 3C 273, 3C 279, 3C 345, BL Lac, and 3C 454.3. No statistically meaningful flux-density changes during an observing interval (1 to 3 days) are detected for any source, and a high degree of correlation between flux-density variations at 85.2 or 90 GHz and those observed at lower frequencies is found in all 10 sources. Some variations observed at different frequencies in several individual sources are briefly discussed.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; Apr. 197
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  • 9
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    Copernicus observations of the Ap star Epsilon Ursae Majoris (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectral scans of the Ap star Epsilon UMa made with the Copernicus satellite show strong line blanketing from profuse Cr II and Fe II lines. In the spectral region covering 1900 to 3000 A, about 500 lines are present which suppress the apparent continuum by at least 15-30%. An accurate line-identification list is compiled showing Eu II present in addition to Mn II and Ni II. The identification of Eu II, however, rests on very stringent identification limits for Fe II. If these are relaxed, the existence of Eu II is dubious. There are no broad features in this spectral region which would suggest strong photoionization discontinuities by metals, but one feature near 2137 A might contain the photoionization edge due to Cr I 5S lying 0.94 eV above the ground level. However, a significant correlation between the line-blanketing strength and the amplitude of the OAO-2 ultraviolet light curves was found such that both monotonically increase in the same proportion toward shorter wavelengths. This gives additional strength to the suggestion that variations in the metal line-blanketing cause the observed photometric variations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series; 33; Jan. 197
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  • 10
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    5 GHz observations of galactic supernova remnants (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Brightness and polarization distributions over several galactic supernova remnants have been observed at a wavelength of 6 cm. These observations have confirmed the nonthermal nature of most of the observed sources. It is suggested, however, that the objects G33.1-0.1 (KES 78), G35.6-0.0, G37.6-0.1, G37.7+0.1, and G37.9-0.4 are thermal. The results of these observations are presented in the form of total intensity contour maps with superimposed polarization vectors.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 55; 1, Fe; Feb. 197
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  • 11
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    Far-ultraviolet imagery of the Barnard Loop Nebula (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An electrographic Schmidt camera carried on a sounding rocket has yielded far-ultraviolet (1050-2000 A and 1230-2000 A) images of the Barnard Loop Nebula and of the general background in the Orion region due to scattering of ultraviolet starlight by interstellar dust particles. The total intensity in the Barnard Loop region agrees well with OAO-2 measurements, but the discrete Loop structure contributes only some 15% of the total. The measurements are consistent with a relatively high albedo for the dust grains in the far-ultraviolet.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 212
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  • 12
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    Apollo-16 far-ultraviolet spectra in the Large Magellanic Cloud (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Spectra in the wavelength ranges from 900 to 1600 A and 1050 to 1600 A of some OB associations in the Large Magellanic Cloud were obtained from the lunar surface by the Apollo-16 far-ultraviolet camera/spectrograph on April 22, 1972. The observed spectral distributions appear consistent with a stellar model having an effective temperature of 30,000 K, reddened by E(B-V) = 0.3, and characterized by the average far-ultraviolet extinction curve of Bless and Savage (1972). However, the absolute intensity of the far-ultraviolet spectrum of the associations NGC 2050 and 2055 seems somewhat too bright in comparison with ground-based photometry.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 211
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  • 13
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    Far infrared observations of IRC + 10216 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for measurements of IRC + 10216 at 100 microns made with the 91-cm telescope of NASA's Kuiper Airborne Infrared Observatory. The IR photometer employed consisted of a gallium-doped germanium photoconductive detector with a MOSFET preamplifier and load resistor. Signals obtained from the source at modulation frequencies of 30 and 100 Hz are plotted, and the 100-micron flux measurements are shown to be in agreement with previous bolometric measurements. It is noted that the sensitivity of the photoconductive detection system is comparable to that of the conventional bolometers that have been used in airborne IR observations.
    Keywords: ASTRONOMY
    Type: Nature; 265; Feb. 10
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  • 14
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    Comets (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The nature and origin of comets is discussed. Observations of the principal parts of comets, the dust and plasma tails, the hydrogen cloud, the coma and the cometary nucleus, are presented, and the icy conglomerate model of Whipple as extended by Delsemme accounting for the observed properties and their variation with heliocentric distance is examined. The origin of comets is considered in relation to the orbital statistics of the long-period comets and the existence of the Oort cloud on the edge of the solar system, and possible roles for comets in the solar nebula and the evolution of the solar system are indicated. Particular attention is then given to the discovery and properties of Halley's Comet, which is expected to reach perihelion in 1986, and to possible flyby and rendezvous missions to Halley's Comet and others.
    Keywords: ASTRONOMY
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  • 15
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    Electron densities for 10 planetary nebulae derived from the semiforbidden C III lambda 1907/1909 ratio. II (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Electron densities for IC 351, IC 2165, J900, IC 3568, NGC 6644, NGC 6891, IC 4997, NGC 7009, Hu 1-2, and IC 5217 are derived from high-dispersion semiforbidden C III spectrograms. For seven of these nebulae, the derived electron density is larger than the values derived from either surface brightness measurements or forbidden line ratios. Only one object, Hu 1-2, shows pronounced splitting of the semiforbidden C III emission lines due to a large expansion velocity.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 16
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    Medium energy gamma ray astronomy with transpacific balloon flights (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Transpacific balloon flights with the University of California, Riverside (UCR) double scatter telescope are discussed. With flight durations from 5 days up to perhaps 15 days the long observation times necessary for medium energy (1-30 MeV) gamma ray astronomy can be obtained. These flights would be made under the auspices of the Joint U.S.-Japan Balloon Flight Program at NASA. It is proposed that flights can provide at least 30 hours of observation time per flight for many discrete source candidates and 120 hours for detecting low intensity cosmic gamma ray bursts.
    Keywords: ASTRONOMY
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  • 17
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    Studies in astronomical time series analysis. I - Modeling random processes in the time domain (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Several random process models in the time domain are defined and discussed. Attention is given to the moving average model, the autoregressive model, and relationships between and combinations of these models. Consideration is then given to methods for investigating pulse structure, procedures of model construction, computational methods, and numerical experiments. A FORTRAN algorithm of time series analysis has been developed which is relatively stable numerically. Results of test cases are given to study the effect of adding noise and of different distributions for the pulse amplitudes. A preliminary analysis of the light curve of the quasar 3C 272 is considered as an example.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series; 45; Jan. 198
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  • 18
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    Three new 'nonterrestrial' molecules (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Eight new interstellar lines have been detected from three molecules not previously observed spectroscopically in space or in the laboratory. One is a linear or nearly linear molecule with microwave constants B0 equals 21,337.15 plus or minus 0.06 MHz, D0 equals 21.4 plus or minus 1.5 kHz. This is the thioformyl ion HCS(plus), first identified because B0 and D0 are close to those calculated, and now confirmed by laboratory detection of one of the present lines (Gudeman et al.). The second molecule, also linear or nearly so, has microwave constants B0 equals 10,691,406 plus or minus 0.043 MHz, D0 equals 1.84 plus or minus 0.91 kHz close to those expected for the isoelectronic systems HOCO(plus) and HOCN; a choice between the two cannot be made on the basis of the available astronomical data. The existence of a third molecule is deduced from an unidentified line at 85,338 MHz that has been found in many sources, is fairly intense in several, and may be self-absorbed in Sgr B2.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 19
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    Discovery of phase-locked variable polarization in an RS Canum Venaticorum-like star, HR 5110 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Using measurements on 79 nights in 1980 January-August, it is established that the polarization in the ultraviolet (U band) varies synchronously on the known binary period of 2.6132 days, with a peak-to-peak amplitude of 0.03%. The pattern is mainly second harmonic in character, as typical of binary star examples such as Algol and Upsilon Her. Reflection by the cooler star, by a plasma concentration, or both, is suggested. The scale of the polarization seems to be consistent with Rayleigh scattering by neutral hydrogen on the cooler star, and a roughly lambda to the -4th wavelength dependence should be searched for. The QU curve suggests a sizeable inclination for the system, of about 45 deg, but this is preliminary. Separately, a possible weak periodicity might be present on a subsidiary period, conceivably related to a rotating star spot.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 20
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    The 45 micron H2O ice band in the Kleinmann-Low Nebula (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 245
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  • 21
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    Concerning the Wolf-Rayet and other luminous early-type stars (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Effective temperatures, radii, and luminosities were determined from S2/68, ANS, UBV, and uvby photometry for four B0/B1 supergiants, four O4 stars, and four WN7/WN8 stars as well as for four test stars having spectral types between B1.5 V and 09 V and five stars with known angular diameters and effective temperatures. The effective temperatures of B1 Ia+ stars are found to be near 17,000 K, those of O4 stars near 45,000, and those of WN7/WN8 stars near 26,000 K. The question of modeling the atmospheres of hot luminous stars is examined, and it is noted that the photosphere can be modeled adequately using a classical plane-parallel layer model atmosphere. In addition, it is found that the Wolf-Rayet stars of types WN7/WN8 fall in the H-R diagram near the B0 Ia stars, while the others fall near B0.5 III stars. The evolutionary relationship between the Wolf-Rayet and O stars is considered; it is suggested that a Wolf-Rayet spectrum is a short-lived phase in the life of a massive star.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 22
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    Observation of the core of the Perseus cluster with the Einstein solid state spectrometer - Cooling gas and elemental abundances (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Solid State Spectrometer observations of the core of the Perseus cluster have resulted in the detection of X-ray emission lines due to Si, S, and Fe. Analysis of the spectrum indicates that the X-ray emission has at least two characteristic temperatures. This is interpreted in the framework of radiative accretion in the core of the cluster. The derived parameters are a cooling time less than or approximately equal to 2 x 10 to the ninth years for the low-temperature gas, a mass accretion rate of approximately 300 solar masses per year, and a characteristic size of 10-20 kpc for the cool gas. The Fe abundance in the core (approximately 0.4) is similar to the Fe abundance averaged over the whole cluster, indicating that Fe emission is not strongly concentrated about NGC 1275. The Si and S abundances are consistent with solar values.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 23
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    Non-linear stability around the triangular libration points (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The configuration space around the triangular libration points in the Earth-Moon system is partitioned according to the stability of the motion. The regions around L4 and L5 are established where particles placed with zero initial velocity will librate. The complexity of the partitioning is revealed.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 23; Mar. 198
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  • 24
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    High-resolution observations of the QSO 3C 345 at 1.3 centimeters (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: High-resolution VLBI observations made at a frequency of 22.235 GHz of the quasar 3C 345 are discussed. Antennas located at the Crimean Astrophysical Observatory, USSR; Onsala, Sweden; Effelsberg, West Germany; and the Haystack Observatory, Massachusetts were employed at 4-min integration times to provide baselines ranging up to 5.5 x 10 to the 8th wavelengths. About 40% of the total flux density of 7.85 Jy, observed in November 1977, and 8.05 Jy, observed in October 1978, is found to originate in an unresolved component of the quasar core in a region less than 0.1 milliarcsec in diameter. The elongated jet-like component of the quasar is observed to contain several peaks of emission extending up to 6 milliarsec from the core which decreased in extent between the two observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 243
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  • 25
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    Radio astronomy (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The activities of the Deep Space Network in support of radio astronomy operations during the first quarter of 1981 are reported. Results of the use of a low noise maser are presented, as well as updates in DSN support of experiments sanctioned by the Radio Astronomy Experiment Selection Panel.
    Keywords: ASTRONOMY
    Type: The Telecommun. and Data Acquisition Rept.; p 1-2
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  • 26
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    High-resolution IUE observations of the 1981 eclipse of 32 CYG (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: 32 Cyg shows a spectacular pure emission line spectrum during eclipse. Six weeks later, most lines, which were observed in emission during eclipse, are seen as P Cygni type profiles with strong absorption components. The lines are formed through line scattering of B star light in the extended atmosphere (wind) of the K supergiant. During eclipse, the emission parts of the P Cyg lines remain visible since the size of the line scattering sphere around the B star is larger than the red giant. Other emission lines are formed in a shock front near the B star (CIV, SiIV, FeIII) and possibly in an accretion disk. The strong FeII UV Mult. 191 lambda lambda 1785-88 A is shown to be formed through optical pumping via FeII UV Mult. 9 photons. The phase dependence of the P Cyg type profiles is modelled by means of line transfer calculations in nonspherical, 3-dimensional geometry with velocity fields.
    Keywords: ASTRONOMY
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 245-259
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  • 27
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    Optical photometry of SS 433 - 200 nights of data 1979-1980 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results from over 200 nights of optical photoelectric photometry of SS 433 during the period July 1979-October 1980 are presented. The data, taken in unfiltered light, the V band, an interference filter band centered on stationary H-alpha and a far-red band, provide evidence for an underlying 164-day light variation of peak-to-peak amplitudes 0.50 magnitude in V and 0.7 magnitude at 6567 A, and a binary-like variation with period 13.074 days and peak-to-peak amplitudes 0.50 and 0.60 magnitudes, respectively. The 13-day light curves are found to change slightly as a function of phase in the 164-day cycle, while seemingly erratic light fluctuations of up to 1 magnitude in 1 day and about 2 magnitudes in 3-4 days are imposed on both cyclic variations. It is noted that a conventional close-binary model is incapable of accounting for all the observed features, and alternatives involving some sort of luminous, rapidly changing extended low-mass envelope or screen in the binary system must be sought.
    Keywords: ASTRONOMY
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  • 28
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    Infrared photometry of comets Bowell and P/Stephan-Oterma (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Broadband IR photometry in the 1-20 micron range of the comets P/Stephan-Oterma and Bowell shows JHK colors similar to P/Meier and P/Tuttle, which are compatible with the scattering of sunlight by micron-sized grains. In addition, the P/Stephan-Oterma thermal emission was found to have an effective temperature higher than that expected from a blackbody in equilibrium. It is demonstrated that the thermal emission can be fit by models of the dust coma consisting of micron-sized grains, and that most of the flux at all observed wavelengths comes from the dust grains rather than the nucleus.
    Keywords: ASTRONOMY
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  • 29
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    X-ray and VLBI radio observations of the quasars NRAO 140 and NRAO 530 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Einstein X-ray Observatory has confirmed the HEAO 1 detection of the NRAO 140 and NRAO 530 quasars, and found that the low-energy X-ray flux of NRAO 140 is consistent with the high-energy results from the earlier satellite. It is also determined that the X-ray emission from NRAO 530 has either decreased by an order of magnitude, from 1978.0 to 1979.7, or the HEAO 1 field contained a second bright source. The two sources have been observed at 2.8 cm, using a four-station intercontinental VLB array, to find whether the X-ray emission is caused by Compton scattering within the radio components. Dissection of the NRAO 140 into its separate components shows radio parameters that imply a 'Compton problem', in that X-ray emission three orders of magnitude greater than that observed is predicted in one of the components if the source is static. Because the effect is independent of distance, relativistic motion with a Lorentz factor greater than about 40 is required to bring the predicted X-ray flux down to the observed value.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 249
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  • 30
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    Observations of SMC X-1 with the monitor proportional counter on the Einstein /HEAO 2/ X-ray Observatory - The pulse period and its history (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The results of the sixth determination of the pulse period of the X-ray source SMC X-1 are presented. The observations were made in April 1979. The pulse period at this epoch was found to be (0.713683 + or - 0.000032) s referred to phase zero of the binary motion. This result together with all available historical data is utilized to quantify the observed trend toward spin-up. It is found that simple secular trends are not applicable. This finding is interpreted as evidence for additional variations in the pulse period. The obtained results are discussed in the context of present theoretical models for period variations in the binary pulsating X-ray sources. The apparent absence of spin-down episodes in the period history of SMC X-1 is also considered.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 31
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    Two-component X-ray emission from RS Canum Venaticorum binaries (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A summary is presented of results from the Solid State Spectrometer on the Einstein Observatory for seven RS CVn binaries. The spectra of all require two emission components, evidenced by line emission characteristics of plasma at 4-million to 8-million K and bremsstrahlung characteristic of 20-million to 100-million K. The data are interpreted in terms of magnetic coronal loops similar to those seen on the sun, although with different characteristic parameters. The emission regions could be defined by separate magnetic structures. For pressures less than 10 dynes/sq cm the low temperature plasma would be confined within the stellar radii, while the high temperature plasma would, for the synchronous, close binaries, fill the binary orbits. However, for loop pressures exceeding 100 dynes sq cm, the high temperature components would also be confined to within the stellar radii, in loops covering only small fractions of the stellar surfaces. While the radio properties and the occurrence of X-ray flares suggest the larger emission regions, the observations of time variations leave the ambiguity unresolved.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 32
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    Pulsar gamma-rays - Spectra, luminosities, and efficiencies (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The general characteristics of pulsar gamma-ray spectra are presented for a model in which the gamma rays are produced by curvature radiation from energetic particles above the polar cap and attenuated by pair production. It is found that the shape of the spectrum depends on pulsar period, magnetic field strength, and primary particle energy. Comparing numerically calculated spectra with the observed spectra of the Crab and Vela pulsars, it is determined that primary particles must be accelerated to energies of approximately 3 x 10 to the 7th m c-squared. A general formula is determined for pulsar gamma-ray luminosity; it is found to depend on period and field strength.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 245
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  • 33
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    The Uranus occultation of 10 June 1979. I - The rings (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 86; Apr. 198
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  • 34
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    Infrared observations of AE Aquarii (1981)
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    Publication Date: 2011-08-18
    Description: Broadband infrared observations of the cataclysmic variable AE Aquarii are reported. The observations were obtained in the J, H, K and L filters with the InSb photometer attached to the 1-m telescope of the European Southern Observatory. The infrared energy distribution observed from 0.35 to 3.5 microns for phase 0.5 suggests a spectral type of K5 V for the secondary and a distance to the system of approximately 70 pc if an absolute magnitude of 7.3 is assumed. Monitoring of the flux at 2.2 microns reveals a variability with an amplitude of approximately 0.3 magnitude over one third of the orbital period, the nature of which is under investigation.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 93
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  • 35
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    An X-ray survey of nine historical novae (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Einstein Observatory Imaging Proportional Counter has been used to search for X-ray emission from nine nearby historical novae. Six of the novae have been detected with estimated X-ray intensities between 0.1 and 4 keV of 10 to the -13th to 10 to the -11th erg/sq cm-sec, comparable to the intensities of previously detected cataclysmic variables. The X-ray intensity of one of the novae, V603 Aql, varies over times of several hundred seconds. The data suggest a correlation between the decay rate of the historical outburst and the current X-ray luminosity. Alternatively, the X-ray luminosity may be related to the inclination of the binary system.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 36
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    Pulsar and diffuse contributions to observed galactic gamma radiation (1981)
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    Publication Date: 2011-08-18
    Description: The first calculation of a gamma-ray production spectrum from pulsars in the Galaxy, along with a statistical analysis of data on 328 known radio pulsars, are presented. The implications of this point source contribution to the general interpretation of the observed galactic gamma-ray spectrum are indicated. The contributions from diffuse interstellar cosmic-ray induced production mechanisms are then re-examined, concluding that pulsars may be contributing significantly to the galactic gamma-ray emission.
    Keywords: ASTRONOMY
    Type: Nature; 290; Mar. 26
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  • 37
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    Variable X-ray spectra of BL Lacertae objects - HEAO 1 observations of PKS 0548 - 322 and 2A 1219 + 305 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 243
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  • 38
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    Phase-correlated P Cygni profile variations of the C III multiplet in UW Canis Majoris (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interacting close binary system UW CMa has been observed, in the wavelength range from 1161 to 1188 A, continuously during a complete orbital cycle in 1979 with the Copernicus (OAO-3) U2 spectrometer. The C III multiplet at 1175 A, observed as a P Cygni feature, exhbits a clear dependence on the orbital phase of the binary; the radial velocity variation of this feature lags behind that of the O7 primary component by 0.1 orbital phase, which agrees with the anticipations in an earlier study by the same authors. The radiation-driven matter, flowing out of the binary, originates in the primary component.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 94; 2, Fe; Feb. 198
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  • 39
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    VRI photometry of selected SAO stars (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Johnson V, R, and I photoelectric photometry has been obtained for 199 SAO stars in support of the Near Infrared Photographic Sky Survey. These data are utilized in the calibration of survey photographs and are presented here to assist other programs reliant upon access to photometry in the photographic infrared.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 92
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  • 40
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    Deformation of a line-element in the phase space at the triangular libration point (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The flow in the projection of the phase space into the configuration space is presented in the neighborhood of a neutrally (or critically) stable equilibrium point in the restricted problem of three bodies. The projection is a line-element every point of which has zero initial velocity. After the elapse of various times the mapping (the rotations and elongations) of the line-element is described showing chaotic behavior.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 23; Feb. 198
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  • 41
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    Stability of outer planetary systems (1981)
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    Publication Date: 2011-08-18
    Description: The conditions for stability in the Liapunov-Hill sense of outer planetary systems are given in terms of radii of planetary orbits. The outer planets of the solar system are found stable and the possible existence of other than the presently known planets between Jupiter and Pluto are indicated. The existence of other planetary systems with arbitrary mass ratios of the primaries is suggested, and the stability conditions for such systems are derived.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 23; Jan. 198
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  • 42
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    In quest of telescopes (1981)
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    Publication Date: 2011-08-18
    Description: This article deals with the author's decision to study star formation and reviews the early days of infrared astronomy at O'Brien Observatory. The infrared equipment used to observe the T Tauri variable class is described.
    Keywords: ASTRONOMY
    Type: Sky and Telescope; 61; Feb. 198
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  • 43
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    Radio astronomy (1981)
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    Publication Date: 2011-08-18
    Description: The activities of the Deep Space Network in support of Radio Astronomy Operations during April and May 1981 are reported. Work in progres in support of an experiment selected for use of the DSN by the Radio Astronomy Experiment Selection Panel, Twin Quasi-Stellar Object VLBI, is reported.
    Keywords: ASTRONOMY
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 1-9
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  • 44
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    Planetary radar (1981)
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    Publication Date: 2011-08-18
    Description: The radar astronomy activities supported by the Deep Space Network during the first quarter of 1981 are reported. The bodies observed include the asteroids Apollo and Toro, comet Bradfield, and the rings of Saturn.
    Keywords: ASTRONOMY
    Type: The Telecommun. and Data Acquisition Rept.; p 226
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  • 45
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    Radio Astronomy (1981)
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    Publication Date: 2011-08-18
    Description: The activities of the DSN in support of Radio and Radar Astronomy Operations during September through December 1980 are described. Emphasis is on a report of an experiment selected for use of the DSN by the radio Astronomy Experiment Selection Panel: that of VLBI observations of the energetic galactic object SS-433.
    Keywords: ASTRONOMY
    Type: Telecommun. and Data Acquisition; p 1-2
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  • 46
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    Spectroscopy of the B-gamma line in the Galactic center (1981)
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    Publication Date: 2011-08-18
    Description: Spectra of the B-gamma recombination line of hydrogen in the Galactic center show that the line has central velocities and shapes similar to those reported previously for the Ne II line. Observations are made at 10 positions within the infrared cluster of the Galactic center with a circular diaphragm of diameter 5 arcsec and with a spectral resolution of approximately 85 km/sec. The spectra confirm that the ionized gas in the Galactic center is distributed in discrete clouds.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 86; Apr. 198
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  • 47
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    The 1980 June X-ray high state of Cygnus X-1 - Optical changes (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: UBV photometry of Cygnus X-1 is reported from before, during, and after the 1980 June X-ray high state discovered by the Hakucho satellite. A darkening was recorded around orbital phase 0.25, also near phase 0.0, which persisted for over a month after the X-ray episode. The brightness around phase 0.75 remained normal. Light curves from preceding years are compared. Preliminary mention is also made of polarization changes during the high state.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 48
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    The NASA/Marshall Space Flight Center program in gamma-ray burst astronomy (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The research program in gamma-ray burst astronomy at the NASA/Marshall Space Flight Center is described. Large-area scintillation detector arrays have been flown on high-altitude balloons, and an array is being developed for the Gamma-Ray Observatory. The design of these detectors is described along with results obtained from previous balloon flights.
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  • 49
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    The Goddard program of gamma-ray transient astronomy (1981)
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    Publication Date: 2011-08-18
    Description: The Goddard program of gamma-ray burst studies is briefly reviewed. The past results, present status and future expectations are outlined regarding our endeavors using experiments on balloons. IMP-6 and IMP-7, OGO-3, ISEE-1 and ISEE-3, Helios-2, Solar Maximum Mission, the Einstein Observatory, Solar Polar and the Gamma Ray Observatory, and with the interplanetary gamma-ray burst networks, to which some of these spacecraft sensors contribute. Additional emphasis is given to the recent discovery of a new type of gamma-ray transient, detected on 5 March, 1979.
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  • 50
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    An investigation of the neutral and ionized gas in M16 (1981)
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    Publication Date: 2011-08-18
    Description: An attempt is made to understand the physical and kinematic conditions in the M16 active star formation site, by means of mapping observations of neutral and ionized hydrogen and observations of (C-12)O from selected positions within the H II regions. The 21-cm maps suggest that at least two neutral clouds are present in the M16 complex, one of which is likely to be the remains of the cloud in which star formation initially occurred, and the other is probably the cold gas remaining from a disrupted cloud edge where the ionization front has crossed the cloud-intercloud boundary. Multislit echelle spectra of the H-alpha line are obtained to determine the physical conditions within the ionized gas, and H-alpha maps show that the ionized gas is systematically blueshifted in the east and splits into two streams in the southwest.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 248
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  • 51
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    The Sixth Catalogue of galactic Wolf-Rayet stars, their past and present (1981)
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    Publication Date: 2011-08-18
    Description: This paper presents the Sixth Catalogue of galactic Wolf-Rayet stars (Pop. I), a short history on the five earlier WR catalogues, improved spectral classification, finding charts, a discussion on related objects, and a review of the current status of Wolf-Rayet star research. The appendix presents a bibliography on most of the Wolf-Rayet literature published since 1867.
    Keywords: ASTRONOMY
    Type: Space Science Reviews; 28; 3, 19; 1981
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  • 52
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    Observations of faint Haro galaxies (1981)
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    Publication Date: 2011-08-18
    Description: Spectroscopic and photometric data for 23 faint-compact UV-excess galaxy candidates, found by Haro's three-color technique (1956), are presented. Eighteen were found to be emission-line galaxies (magnitudes between 14.4 and 17.9) with redshifts in the range of 1670 to 39,450 km/s; the remaining five appear to be stars. The apparent compactness of the galaxy images is a result of the finite resolution of the Survey plates. Faint Haro galaxies are not distinguishable from the original Haro galaxies in surface brightness or in their range of color and absolute magnitude. The Haro galaxies correspond to roughly two-thirds of Huchra's non-Seyfert Markarian galaxies (1977 a) which have the most negative (U-B) index; the new Haro galaxies have the same V magnitude growth with aperture, the same (B-V) aperture relation, and the same mean surface brightness as the Markarian galaxies.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 93
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  • 53
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    Far-ultraviolet imagery of the Orion Nebula (1977)
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    Publication Date: 2011-08-17
    Description: Two electrographic cameras carried on a sounding rocket have yielded useful-resolution far-ultraviolet (1000-2000 A) imagery of the Orion Nebula. The brightness distribution in the images is consistent with a primary source which is due to scattering of starlight by dust grains, although an emission-line contribution, particularly in the fainter outer regions, is not ruled out. The results are consistent with an albedo of the dust grains that is high in the far-ultraviolet and which increases toward shorter wavelengths below 1230 A.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
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  • 54
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    OSO-8 X-ray observations of AM Herculis (1977)
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    Publication Date: 2011-08-17
    Description: Results are reported for hard X-ray observations of the binary system AM Her, which were coincident with soft X-ray and ground-based optical measurements. In the 2-60-keV band, variability was detected with an eclipse during phases 0.5 to 0.7 with respect to the 0.12892-day optical minima, synchronous with the known soft X-ray eclipse. The 2-60-keV uneclipsed flux was 9.5 by 10 to the -10th power erg/sq cm per sec, of which 86% lies above 10 keV. Thus, AM Her contains a hard source located near the similarly eclipsed soft X-ray source. The X-ray data are interpreted in terms of thermal bremsstrahlung from accretion onto a white dwarf.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 55
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    The far-infrared spectrum of the core of Sagittarius B2 (1977)
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    Publication Date: 2011-08-17
    Description: A Michelson interferometer aboard NASA's Kuiper Airborne Observatory has been used to measure the spectrum of Sgr B2 from 40 to 200 kaysers with 5-kayser resolution in a 1.4-arcmin beam. The measured spectrum is smooth and featureless with a broad maximum at about 85 kaysers. The data can be fitted analytically with a model corresponding to thermal emission by a uniform sla of dust filling the beam, with an average temperature of approximately 32 K, an optical depth at 100 microns of about 1.6, and a spectral index of the dust emissivity about 1.5. The absence of features implies either that the source is optically thick or that the emission spectrum of the individual grains is smooth in the passband. The possible physical significance of this model is discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 56
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    X-ray spectra of Hercules X-1. II - The pulse (1977)
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 57
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    A1540-53, an eclipsing X-ray binary pulsator (1977)
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    Publication Date: 2011-08-17
    Description: An eclipsing X-ray binary pulsator consistent with the location of A1540-53 has been observed. The source pulse period was 528.93 + or - 0.10 s. The binary nature is confirmed by a Doppler curve for the pulsation period. The eclipse angle of 30.5 + or - 3 deg and the 4-hour transition to and from eclipse suggest an early-type giant or supergiant primary star.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 58
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    The spectral development of Nova Cygni 1975 (1977)
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    Publication Date: 2011-08-17
    Description: Optical and near-infrared (0.3-2.5 microns) observations of Nova Cygni 1975 made during the period from August 30 to December 11, 1975, are reported. The persistent strength of O I at 8446 and 11,287 A is shown to be due to L-beta fluorescence in clouds with high (greater than 1000) H-alpha optical depth. A simple model of the nova ejecta is presented and shown to be consistent with the observed evolution of the nova spectrum.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 59
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    Radar detectability of asteroids - A survey of opportunities for 1977 through 1987 (1977)
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    Publication Date: 2011-08-17
    Description: The study of asteroids by earth-based radar during the period 1977 to 1987 is discussed. Detection modeling, including backscattering laws, limits of detectability, and in particular, measurement of center frequency, center-to-limb bandwidth, and areal spectral density, is reviewed. The number of detectable objects and detectable events falling into various 5-decibel radar target loss slots is estimated; a total of 60 different asteroids should be observable on about 130 occasions by either the Goldstone or Arecibo radar systems during the decade considered. Furthermore, the detectability margins for many objects should be large enough to permit more refined analysis of the radar spectrograms. Data acquired during the ten-year period may be used to find the radius, average surface roughness, rotation rate, direction of polar axis, and estimates of the Doppler frequency offsets for many of the asteroids. Also, information about radar albedos and orbital parameters may be obtainable in a number of cases.
    Keywords: ASTRONOMY
    Type: Icarus; 31; Aug. 197
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  • 60
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    UBV photometry of small and distant asteroids (1977)
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    Publication Date: 2011-08-17
    Description: Photoelectric magnitudes and colors on the ultraviolet (UBV) system are presented for 65 minor planets, including four Mars crossers, six Trojans, and main-belt objects down to 6 km in diameter. The Trojans all have very similar colors not characteristic of the main-belt population. A paucity of S-type asteroids at the smallest diameters, predicted from trends seen at larger sizes, is not observed. The newly available color data for small objects ranging from 1.0 to 5.2 astronomic units in heliocentric distance show the main belt to be a transition zone between predominantly silicate and carbonaceous compositions.
    Keywords: ASTRONOMY
    Type: Icarus; 31; Aug. 197
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  • 61
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    Effect of the Shuttle contaminant environment on a sensitive infrared telescope (1977)
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    Publication Date: 2011-08-17
    Description: A sensitive IR telescope on the Space Shuttle Orbiter will be limited in its performance by fluctuations in the IR radiation from the natural environment and the contaminant atmosphere. Models of the Orbiter's contaminant atmosphere were used to predict its spectral radiance from 3 to 300 microns. At 350 km, statistical fluctuations in the radiation from a water vapor column, and a noise equivalent power were measured. This noise is somewhat smaller than the expected contribution from zodiacal light from 5 to 30 microns. The column density of all IR emitting molecules can be kept low only if restrictions on rocket firings and liquid vents are maintained. The relatively low frequency of particle sightings from Skylab, coupled with improvements in Orbiter venting techniques, indicate that sightings of particles 2 microns and larger in radius will not seriously hamper telescope performance provided that liquid vents and rocket firings are properly restricted.
    Keywords: ASTRONOMY
    Type: Applied Optics; 16; Aug. 197
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  • 62
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    A new optical supernova remnant in Cygnus (1977)
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    Publication Date: 2011-08-17
    Description: The letter reports the discovery of a filamentary emission-line structure at right ascension 19 hr 31 min and declination +31 deg 10 min (1950) during an emission-line survey of the Milky Way. This structure is classified as a supernova remnant on the basis of its similarity to several other SNRs, but is shown not to be part of the Gamma Cygni complex. A physical diameter of about 70 pc is obtained for this SNR along with a distance of approximately 1200 pc, a shock velocity of at least 50 km/s, an initial density of about 0.5 per cu cm, and an age of approximately 300,000 yr.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 215
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  • 63
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    The ultraviolet spectra of four binaries observed with the S59 spectrometer (1977)
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    Publication Date: 2011-08-17
    Description: Ultraviolet spectra of Omicron And, Alpha CrB, Eta Ori A, and Alpha Vir, which were obtained with the S59 spectrometer at a resolution of 1.7 A in three 100-A-wide regions centered at 2110, 2454, and 2825 A, have been studied for the presence or absence of effects due to their binary nature. As may have been anticipated from their orbital and other characteristics, no indication of strong binary interactions were seen in these observations. However, there are certain spectral peculiarities suggesting the possibility of modifications of spectral classifications for some of these objects. A rather unusual spectral behavior in Alpha Vir is also noted. In addition, based primarily on a review of available literature, attention is drawn to a remarkable property of the third component in Eta Ori A.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science; 46; Feb. 197
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  • 64
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    Spectroscopic studies of very old hot stars. II - Spectral classification, absolute magnitudes, and distances of O-type planetary nuclei (1977)
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 215
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  • 65
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    Orbital evolution (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The orbital evolution of a large satellite is governed primarily by tidal interactions between the satellite and the planet it orbits. Tides raised on a planet by a satellite transfer energy and angular momentum to the satellite orbit; this changes the semimajor axes of satellite orbits, increasing the size of those orbits where the satellite mean motion is smaller than the planetary angular velocity, and decreasing those where the opposite is true. Substantial changes caused by such tides for satellites of the terrestrial planets may explain the absence of satellites about Mercury and Venus. For Jovian and Saturnian satellites, such tides probably are only important in bringing about some of the observed orbital resonances. Tides raised on satellites generally cause decreasing orbital eccentricities, indicating why close satellites always have nearly circular orbits. Different processes of orbital evolution dominate for small bodies; their effects probably are critical in positioning material in the primordial dust cloud so that satellite coagulation may occur. A qualitative description is given of the orbital results of gas drag, radiation pressure, Poynting-Robertson drag and electromagnetic forces.
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    Black holes and relativitic gravity theories (1977)
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    Publication Date: 2011-08-17
    Description: All presently known relativistic gravitation theories were considered which have a Riemannian background geometry and possess exact static, spherically symmetric solutions which are asymptotically flat. Each theory predicts the existence of trapped surfaces (black holes). For a general static isotropic metric, MACSYMA was used to compute the Newman-Penrose equations, the black hole radius, the impact parameter, and capture radius for photon accretion. These results were then applied to several of the better known gravitation theories.
    Keywords: ASTRONOMY
    Type: NASA. Langley Res. Center Proc. of the 1977 MACSYMA Users' Conf. (NASA); p 97-107
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  • 67
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    Gamma-ray astronomy in the medium energy (10-50 MeV) range (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: To observe the medium energy component of the intense galactic center gamma-ray emission, two balloon flights of a medium energy gamma-ray spark chamber telescope were flown in Brazil in 1975. The results indicate the emission is higher than previously thought and above the predictions of a theoretical model proposed.
    Keywords: ASTRONOMY
    Type: ESA Recent Advan. in Gamma-Ray Astronomy; p 117-124
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  • 68
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    Survey of the BY Draconis syndrome among dMe stars (1977)
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    Publication Date: 2011-08-17
    Description: Results are reported for a BVr photometric survey of 22 dK, dKe, dM, and dMe stars conducted to search for slow quasi-sinusoidal fluctuations in V (the BY Draconis syndrome). The (B-V) and (V-r) color indices are determined in an attempt to detect wavelength-dependent color changes produced by starspots and to infer starspot temperatures. It is found that nine of the stars exhibit variations in V of the order of 0.05 to 0.10 magnitude on a time scale of days or weeks, that at least three more display changes in mean light level over a period of years, that the stars generally tend to become redder at minimum light, and that some of the stars show no detectable color changes over their photometric cycle. The color data are taken to suggest a probable temperature difference of about 200 to 500 K between the stellar photospheres and starspots if the V variations are attributed to dark spots. It is concluded that the BY Draconis syndrome is clearly a very common occurrence among dMe stars.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; Nov. 197
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  • 69
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    Antenna concepts for interstellar search systems (1977)
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    Publication Date: 2011-08-17
    Description: An evaluation is made of microwave receiving systems designed to search for signals from extraterrestrial intelligence. Specific design concepts are analyzed parametrically to determine whether the optimum antenna system location is on earth, in space, or on the moon. Parameters considered include the hypothesized number of transmitting civilizations, the number of stars that must be searched to give any desired probability of receiving a signal, the antenna collecting area, the search time, the search range, and the cost. This analysis suggests that (1) search systems based on the moon are not cost-competitive, (2) if the search is extended only a few hundred light years from the earth, a Cyclops-type array on earth may be the most cost-effective system, (3) for a search extending to 500 light years or more, a substantial cost and search-time advantage can be achieved with a large spherical reflector in space with multiple feeds, (4) radio frequency interference shields can be provided for space systems, and (5) cost can range from a few hundred million to tens of billions of dollars, depending on the parameter values assumed.
    Keywords: ASTRONOMY
    Type: Radio Science; 12; Sept
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  • 70
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    A solar extreme ultraviolet telescope and spectrograph for Shuttle/Spacelab (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An instrument for advanced studies of the solar corona is described. Its optical system provides nearly stigmatic imaging of selected portions of the sun over the spectral range from 22.5 to 44.0 nm. Both spectroheliograms and emission line profiles of coronal features will be obtained over a wide range of coronal temperatures.
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  • 71
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    The Solar Optical Telescope /SOT/ (1981)
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    Publication Date: 2011-08-18
    Description: The Solar Optical Telescope (SOT) is a 1-m class, high resolution solar telescope which NASA plans to operate on the Shuttle Spacelab during the mid and late 1980's. SOT will provide resolution down to 0.1 arcsec, and can therefore be used to solve many problems of solar atmosphere structure and dynamics. In particular, SOT should provide definite data on (1) the source of the sun's magnetic field, (2) the amount of power in waves generated in the photosphere, (3) the heating of the chromosphere, and (4) the local and global mass and energy balance in the solar transition region. The SOT Scientific Working Group will help plan, develop, and update the overall scientific plan for the SOT, as well as make recommendations with regard to the SOT project, instrumentation optimization, and scientific data management.
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  • 72
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    The planetary nebula NGC 6826 (1981)
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    Publication Date: 2011-08-18
    Description: Monochromatic photographs have established the NGC 6826 nebula as the third member of a group of very rare triple-shell planetaries (Feibelman, 1971, 1974). Kaler (1974) also characterized NGC 6826 as a giant halo planetary. Numerous errors and confusing statements regarding its size, structure and stratification are discussed, and the correct dimensions of the nebula are reported: the inner ring is 12.7 arcsec x 8.7 arcsec (Feibelman, 1971); the outer ring is 27 arcsec x 24 arcsec according to Curtis (1918), 25.7 arcsec x 24.4 arcsec according to Feibelman (1971), and 36 arcsec x 36 arcsec according to Coleman et al. (1975). The halo measurements range in diameter from 110 arcsec (Duncan, 1937) to 130 arcsec (Kaler, 1974) to 142 arcsec (Millikan, 1974). Values for the distance of NGC 6826 range from 0.75-1.16 kpc (Cahn and Kaler, 1971) to 2.265 kpc (Cudworth, 1974).
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 93
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  • 73
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    On the definition of albedo and application to irregular particles (1981)
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    Publication Date: 2011-08-18
    Description: The various definitions of albedo used in planetary astronomy are reviewed. In particular, the Bond albedo, which refers only to the reflected and refracted components, is not applicable to small particles or highly irregular particles, where diffraction is not restricted to a well-defined lobe at small scattering angles. Measured scattering functions for irregular particles are presented in a normalized form and are applied to the case of zodiacal light.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 104; 1, De; Dec. 198
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  • 74
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    Rapid X-ray variability in the Seyfert galaxy NGC 6814 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: In contrast with the Tennant et al (1981) sample of over 30 active galactic nuclei, HEAO 1 A-2 high time resolution X-ray observations of the X-ray emitting Seyfert 1 galaxy NGC 6814 show strong X-ray variability on time scales of less than 3 hr. On a time scale of 90 min, the mean flux varied by a factor of about 2.5, and a characteristic time for variability of 100 + 60 or - 25 sec is obtained by autocorrelation analysis. There is no indication of spectral variability with an upper limit on a change in the power law spectral index of less than about 0.37, for a factor 2 change in intensity. The constraints of such rapid variability on a range of X-ray source mechanisms is discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 251
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  • 75
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    The X-ray structure of Centaurus A (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Einstein X-ray observatory imaging detectors have found X-ray emission associated with several components of the nearby radio galaxy Cen A = NGC 5128: (1) the compact nucleus; (2) an X-ray jet pointed toward the NE radio lobes; (3) the middle NE radio lobe; (4) the disk or dust lane; and (5) diffuse emission extending several arcmin around the nucleus. The intensity of the nucleus changed by a factor of seven over six months. The X-ray jet is considered in terms of thermal, inverse Compton, and synchrotron models. The emission of the NE radio lobe is greater than that expected from inverse Compton or synchrotron processes. Two ridges of emission are found along each edge of the dust lane, within several arcmin of the nucleus. The diffuse X-ray component has a luminosity which is too high to be due to bulge population X-ray sources, but which may be produced by main sequence stars under appropriate circumstances.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 251
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  • 76
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    Positions of three X-ray burst sources (1977)
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    Publication Date: 2011-08-17
    Description: Precise (20-30 arcsec) positions are reported for three steady X-ray sources that have been identified recently as X-ray burst sources: 4U (MXB) 1636-53, 4U 1728-33 (MXB 1728-34), and 4U (MXB) 1735-44. The positions were derived from data obtained with the SAS 3 rotating modulation collimators during a survey of the galactic plane. Possible optical counterparts are noted.
    Keywords: ASTRONOMY
    Type: Nature; 270; Nov. 24
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  • 77
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    Spatial observations of the Orion Nebula in the unidentified 3.28 micron feature (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The unidentified infrared emission at a wavelength of 3.28 microns has been mapped in a 5 x 5 arcmin region of the Orion Nebula at a resolution of 30 arcsec along with continuum thermal emission at 3.5 microns in order to gain information on the probable source of the unidentified feature. The 3.28-micron emission is found to be extended over much of the nebula with a distribution very different from that of the 3.5-micron continuum. The ratio of 3.28-micron to 3.5-micron flux density is observed to range from a value of 7 in the Orion ionization ridge to less than 0.15 towards the Becklin-Neugebauer object, and to generally be larger toward the edges of the emitting region than toward the Trapezium. From the observations, it is concluded that the 3.28-micron emission originates in the ionization front between the foreground ionized gas and background molecular cloud, and may be due to thermal emission from complex, less volatile organic substances in grain mantles.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 245
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  • 78
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    Future prospects for gamma-ray astronomy (1981)
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    Publication Date: 2011-08-18
    Description: As gamma-ray astronomy moves from the discovery to the exploratory phase, the promise of gamma-ray astrophysics noted by theorists in the late 1940s and 1950s is beginning to be realized. In the future, satellites should carry instruments that will have over an order of magnitude greater sensitivity than those flown thus far, and, for at least some portions of the gamma-ray energy range, these detectors will also have substantially improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance our knowledge of several astrophysical phenomena including the very energetic and nuclear processes associated with compact objects, astrophysical nucleosynthesis, solar particle acceleration, the chemical composition of the planets and other bodies of the solar system, the structure of our galaxy, the origin and dynamic pressure effects of the cosmic rays, high energy particles and energetic processes in other galaxies especially active ones, and the degree of matter-antimatter symmetry of the universe. The gamma-ray results of the forthcoming programs such as Gamma-I, the Gamma Ray Observatory, the gamma-ray burst network, Solar Polar, and very high energy gamma-ray telescopes on the ground will almost certainly provide justification for more sophisticated telescopes. These advanced instruments might be placed on the Space Platform currently under study by N.A.S.A.
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    The properties of close multiple stars (1981)
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    Publication Date: 2011-08-18
    Description: A reexamination of the properties of close multiple systems is conducted, taking into account recent numerical, analytical, and observational results. The orbital elements of 43 spectroscopic multiple systems are presented in a table. Tables with photometry data of the systems and data describing their properties are also provided. Attention is given to period ratios, mass ratios, orbital coplanarity, stability, lithium abundances and age estimates, and prospects of future observations. Numerical studies indicate that fragmentation produces binary components with mass ratios usually close to 1.0, while fission usually produces mass ratios in the range 0.1-0.5. Using analytical stability criteria, all 27 close multiple systems considered are stable if they are corotating. If they are counter-rotating, four systems are possibly unstable. However, other factors suggest that even these four are probably stable. The solar-type close multiple systems ranged in age from 100 million years to 2,000 million years.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 80
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    HD 202908 - A young, solar-type triple system (1981)
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    Publication Date: 2011-08-18
    Description: HD 202908 is a solar-type, spectroscopic-visual triple system. High-dispersion spectroscopic observations show that the primary visual component is a double-lined spectroscopic binary with a period of 3.966 days and a mass ratio of 1.0. Velocity changes due to motion in the long-period, 76-year orbit are now perceptible. Over the next 5 years, these changes may amount to 30 km/s for the single star. Continued spectroscopic and visual observations through nodal and periastron passage of the highly eccentric visual orbit, which will occur nearly simultaneously about 1985.5, will permit the accurate determination of the masses and luminosities of the three components. Contrary to expectation, the short-period and long-period orbits are not coplanar. The large lithium abundances, strength of the Ca II emission lines, and rotational velocities all suggest that this multiple system has an age similar to that of the Hyades cluster.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 248
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  • 81
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    Infrared charge-injection-device array performance at low background (1981)
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    Publication Date: 2011-08-18
    Description: Low-background tests of a 1 x 32 Si:Bi charge-injection-device (CID) IR detector are carried out to evaluate its feasibility for space-based astronomical observations. Optimum performance is obtained at a temperature of 11 K. The sensitivity is found to compare well with that of discrete extrinsic silicon photoconductors. The measured sensitivity and the apparent absence of anomalous effects make extrinsic silicon CID arrays very promising for astronomical applications.
    Keywords: ASTRONOMY
    Type: Applied Optics; 20; Sept. 15
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  • 82
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    High-resolution rocket spectra of the 1920-A and 1720-A features in the spectrum of Zeta Tauri (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: High-resolution ultraviolet spectrograms of the B-shell star Zeta Tau reveal two features characteristic of B supergiants, one at 1720 A and the other at 1920 A. The presence of these features in the spectrum of this object shows that they are indicative of an extended atmosphere - either the tenuous atmosphere of a supergiant or the envelope surrounding a rapidly rotating main-sequence star - and are therefore not purely luminosity criteria. The high spectral resolution allows an identification of the contributors to these features. The dominant contributor to the 1920-A feature is Fe III, while the primary contributor to the 1720-A feature is Al II.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
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  • 83
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    Trajectories and orbits from the NASA-NMSU Meteor Observatory. II (1977)
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    Publication Date: 2011-08-17
    Description: Trajectory data and orbital elements for 12 double-station meteors photographed by the NASA-NMSU Meteor Observatory during the winter of 1975-1976 are presented. Three of these are members of the Quadrantid stream. Photoelectric timing of meteors, uncertainties in the derived orbital elements, and monitoring of the night sky with a two-channel photometer are discussed.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; June 197
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  • 84
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    Optical contamination - Its prevention in the XUV spectrographs flown by the U.S. Naval Research Laboratory in the Apollo Telescope Mount (1977)
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    Publication Date: 2011-08-17
    Description: During construction and testing of the XUV spectrographs flown in the ATM by the Naval Research Laboratory, many problems associated with optical contamination were encountered. Solving these problems required setting up a contamination prevention program to select the materials used in constructing the instruments and to delineate procedures in assembling, testing, and storing the instruments. A brief description is given of methods of assessing the effects of contamination and of the procedures used to prevent contamination.
    Keywords: ASTRONOMY
    Type: Applied Optics; 16; Apr. 197
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  • 85
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    The high-energy celestial X-ray instrument on board OSO-8 (1977)
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    Publication Date: 2011-08-17
    Description: The 20 keV-3 MeV celestial X-ray detector on the OSO-8 is described. The primary objectives of this instrument are to measure the energy spectrum of cosmic X-ray sources above 20 keV and to search for time variations, both periodic and irregular, in the intensity of the sources detected. The detector consists of two optically isolated central crystals shielded by a large, active collimator. The sensitive area is 27.5 sq cm and the field-of-view is 5 deg FWHM. The instrument is mounted in the wheel section of OSO-8 with the axis of its field of view offset by 5 deg from the negative spin axis of the wheel. The minimum detectable intensity of a point source which is brought to within 5 deg of the negative spin axis for greater than one day is about 10 to the minus fifth power photons/sq cm-sec at 100 keV.
    Keywords: ASTRONOMY
    Type: Space Science Instrumentation; 3; Nov. 197
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  • 86
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    NH3 spectral line measurements on earth and Jupiter using a 10 micron superheterodyne receiver (1977)
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
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  • 87
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    Theory of thin-screen scintillations for a spherical wave (1977)
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    Publication Date: 2011-08-17
    Description: A thin-screen scintillation theory for a spherical wave is presented under the 'quasi-optical' approximation. The 'scattering angle', the 'observed angle', the intensity correlation function, and the temporal pulse broadening are calculated for the random wave. It is found that as the wave propagates outward away from the phase screen, the correlation scale of the intensity fluctuation increases linearly while the 'observed angle' decreases linearly. The calculations are carried out for both Gaussian and power-law spectra of the turbulent medium. The results are applied to an analysis of the scattering data for the Crab Nebula's radiation.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 218
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  • 88
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    Apparent wavelength dependence of v sin i for Zeta Tauri (1977)
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    Publication Date: 2011-08-17
    Description: It was previously reported that the derived projected rotational velocity (v sin i) of the B shell star, Zeta Tau, appeared to depend on the wavelength of the line used in the analysis. This letter documents the apparent wavelength dependence of v sin i for Zeta Tau in order to provide an observational basis against which quantitative explanations can be tested. A value of 300 km/s is adopted for v sin i on the basis of an examination of the visual line spectrum, particularly the lines of He I at 4026 and 4471 A and Mg II at 4481 A. Analysis of the far-UV resonance lines of Si III at 1206 A and Si IV at 1393 and 1463 A in Copernicus spectrograms of Zeta Tau yields a representative value of no more than 150 km/s for v sin i. Gravity darkening of the star's atmosphere and distention of the atmosphere by rapid differential rotation are considered as possible explanations for the discrepancy between the v sin i values determined from the UV and visual lines.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 218
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  • 89
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    Positions of galactic X-ray sources Cir X-1, TrA X-1 and 3U1626-67 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Nature; 269; Oct. 6
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  • 90
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    An element formulation for perturbed motion about the center of mass (1977)
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    Publication Date: 2011-08-17
    Description: The perturbed motion of a rigid body about its center of mass, is formulated in terms of the six elements: l, the magnitude of the angular momentum vector; h, the total energy; delta and epsilon, two linear functions of the independent variable; and psi(1) and theta (1), two Euler angles that orientate the inertial frame with respect to the unperturbed solution. Solutions from the element formulation and the original Euler equations are numerically compared using shuttle-type data. For applied torques smaller than a given magnitude, the element formulation produced the following results: (1) larger step sizes in the numerical integration of the differential equations, resulting in an overall computational time-saving, and (2) more significant figures of accuracy in the computation of the variables describing the state of the rigid body.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 16; Nov. 197
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  • 91
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    The Tidbinbilla interferometer (1977)
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    Publication Date: 2011-08-17
    Description: This paper describes a technique to detect and identify weak, small-diameter radio sources with flux densities in the millijansky range. An interferometer system is proposed which will use existing 64 m and 24 m antennas of the Tidbinbilla Deep Space Network near Canberra. Design parameters of the system are described, and a schematic is presented with attention to low-noise traveling wave masers, and phase oscillation devices.
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  • 92
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    Optical monitoring of 15 quasars (1981)
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    Publication Date: 2011-08-18
    Description: The data of fifteen quasars are analyzed to determine how well a short-term program of observation can characterize the general optical behavior as compared to a long-term program. Three major research objectives were pursued, namely, to measure archival brightness of the quasars, to compare the brightness observed (mid-1970) to that of the Harvard historical plate collection 1900-1950, and to compare the general behavior during a short-time (two years) to that found over 50 years. Results show that in eight of the 15 quasars the mean magnitude derived from the present short-epoch program differed by 0.11 mag or less from the mean determined in the long-epoch program. The mean difference for all 15 quasars was 0.20 mag. However, in two cases, the short program failed by 0.83 and 0.66 mag, respectively, in predicting the mean brightness. The largest rate of increase in brightness observed was 0.9 mag/day (3C263) and of decrease was 0.44 (3C345), and it is concluded that the rates of decrease and increase in brightness are essentially the same.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 86; May 1981
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  • 93
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    Determination of the potential in a synodic system (1981)
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    Publication Date: 2011-08-18
    Description: Determination of the potential field in a fixed (inertial) system may be accomplished by the solution of a homogeneous linear partial differential equation when a family of orbits of a body moving in the field is given. This partial differential equation was presented and thoroughly analyzed earlier. The present paper discusses the same problem in a rotating system where the centrifugal and Coriolis effects render the pertinent partial differential equation in general non-homogeneous and non-linear. A linear, though non-homogeneous, partial differential equation for the determination of the synodic potential is obtained only in the special case of iso-energetic families of orbits.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 24; May 1981
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  • 94
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    Measurements of forbidden line radiation of Ar II /6.99 microns/ in W3 IRS 1 (1981)
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 95
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    Morphological study of the time histories of gamma-ray bursts (1981)
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    Publication Date: 2011-08-18
    Description: Time histories of gamma-ray bursts have revealed a great diversity, both in total duration and in the details of fine time structure. Results of the gamma-ray experiment on the Helios-2 spacecraft have suggested some similarities in time profiles of events. The possibility of some characteristic 'separation times' in events may also be indicated.
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  • 96
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    High-speed photometry of the 11 December 1979 Juno occultation (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The occultation of SAO 115946 by Juno on 11 December 1979 was observed from two sites in southern California with portable two-color, high-speed photometers. A composite light curve was constructed from the data by suitable scaling of individual observations, using an astrometric solution for the location of the contact points on Juno's limb. The preliminary astrometric solution used here has a semiminor axis of 118 km and a semimajor axis of 145 km at position angle 75.5 deg. The composite light curve is compatible with a stellar radius of (1.6 + or - 0.8) x 10 to the -4th arcsec, consistent with the radius estimated from the color and visual magnitude. There is no evidence for any companions to SAO 115946 or Juno. The prospects for use of asteroid occultations to determine stellar radii and asteroid surface slopes are discussed as compared with the lunar occultation technique.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 86; Jan. 198
    Format: text
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  • 97
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    A 5.57 hour modulation of the X-ray flux from 4U 1822-37 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The X-ray flux of 4U 1822-37 is shown to be modulated with the 5.57 hr period of its optical counterpart. The X-ray light curve is two component, with a smooth sinusoidal-like 25% semiamplitude modulation and a 30 minute dip of approximately 0.2 in phase following the other minimum; the dip center occurs 0.04 in phase after the optical minimum. The X-ray spectrum is a relatively flat power law up to 17 keV, above which it steepens; iron emission is detected at 6.7 keV with a 4 keV FWHM and an equivalent width of 1100 eV. An excess below 2 keV is consistent with either a 0.25 keV thermal component of 350 eV equivalent width iron L emission. Modeling the eclipse for a 0.5-0.7 solar radius companion gives a system inclination of 70-79 deg and a spherical cloud radius of 0.2-0.3 solar radius. Models for the long-term modulation are considered, and a comparison of the properties of 4U 1822-37 with those of Cyg X-3 shows that they are similar systems.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 247
    Format: text
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  • 98
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    Extremely red compact radio sources - The empty field objects (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Radiation of 10 microns has been detected from 1413+135, one of the very red objects discovered by Rieke, Lebofsky, and Kinman (1979) at near-infrared wavelengths. The spectrum of this object flattens at wavelengths longer than 2.2 microns. Upper limits are also given for the 10-micron emission from 2255+14, 0026+34, and 0406+121. Photometry between 1.25 and 2.2 microns confirms the variability of 1413+135, 2255+41, and 0406+121. Five percent resolution spectra of 1413+135 and 0406+121 between 1.5 and 2.4 microns show no emission or absorption lines. The spectral data rule out the possibility that 1413+135 is a quasar with normal line strengths and a redshift less than 1.3 and greater than 4. The lack of features of the 1.5-2.4-micron spectra, the rapid variability, and the overall shape of the radio, infrared, and X-ray energy distributions are consistent with a BL Lac nature for these objects.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 247
    Format: text
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  • 99
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    Are we beginning to understand T Tauri stars (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An international meeting of astronomers in April 1981 in Portugal to discuss recent data on T Tauri stars is described. It is pointed out that T Tauri stars all vary irregularly in brightness, occur in intimate association with dusty molecular clouds, and exhibit bright optical emission lines, principally of hydrogen, helium, and iron. Stars with masses roughly 0.2 to three times the sun's and with ages from 100,000 to 1,000,000 years are typical of the T Tauri regime. It is thought that the often rich emission-line spectra seen at visible wavelengths indicate the presence of a stellar chromosphere, where the temperature rises steeply from the usual cool photospheric values around 4,000 to 5,000 K. Even though a recent extensive survey of T Tauri stars has been completed, no clear role for rotation in producing radio emission or stellar winds has yet emerged.
    Keywords: ASTRONOMY
    Type: Sky and Telescope; 62; Oct. 198
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  • 100
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    The Space Telescope (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Space Telescope, still under construction, is discussed in light of the constraints imposed on ground-based telescopes. The history of the Space Telescope is traced from its conceptual origin to its actual construction, and design considerations used to determine the Space Telescope construction are described. The optical system of the telescope will have an aperture of 2.4 m, a focal ratio of 24, and a front of primary to focus of 1.5 m. The fine guidance system will use astigmatic images at the edge of the field of view to provide the guidance signal for maintaining stability to 0.007 arcseconds. The guidestars are required for 85% of random fields located at the galactic poles, and the system sensitivity must meet performance specifications for stars brighter than 13.5 magnitude. The scientific instruments - the wide field camera, the faint object camera, the faint object spectrograph, the high resolution spectrograph, the high speed photometer, and the fine guidance sensors - are discussed in detail. Finally, the operations system, including schedule contraints and the Science Institute, is presented.
    Keywords: ASTRONOMY
    Format: text
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