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  • Other Sources  (1,733)
  • ASTRONOMY  (1,733)
  • 1980-1984  (1,733)
  • 1930-1934
  • 101
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    The observation, detection and research on satellites of asteroids (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Evidence is presented for the existence of asteroidal satellites. Instances wherein the occultation of a star occurred when a known asteroid was close to the line of sight of the star are discussed, and the implication that the eclipses were caused by satellites of the asteroids is considered. The role of amateur astronomers in these observations is reviewed, and possible applications of the technique of indirect occultation with regard to the solar system are discussed.
    Keywords: ASTRONOMY
    Type: L'Astronomie; 94; July-Aug
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  • 102
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    Effect of solar radiation on a swarm of meteoric particles (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The theory of the Poynting-Robertson effect is used to study the motion of meteors relative to a parent comet describing an undisturbed elliptical orbit. It is shown that any emitted particle proceeds to move retrogressively away from the comet to a certain maximum angular distance (as seen from the sun) depending on its sigma-s value, and then undergoes relative motion in the opposite forward direction. The time taken to reach this greatest elongation behind the comet is the same for all particles, and after twice this time the particles will have returned to zero angular displacement relative to the comet. For comet Encke the time for the elongation to return to zero is about 6600 y; for Halley it is about 200,000 y; for Temple-Tuttle (1965 IV) it is just over 100,000 y.
    Keywords: ASTRONOMY
    Type: Moon and the Planets; 23; Aug. 198
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  • 103
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    VLBI observations at 18 and 2.8 cm - 0133 + 47, 0735 + 178, OH 471, OQ 172, 1633 + 38, and NRAO 667 /2147 + 145/ (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 85; June 198
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  • 104
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    Molecular line observations of AFGL sources (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: HCN and (with three exceptions) CH emission lines have been detected from 14 molecular clouds associated with AFGL sources and/or Sharpless regions. Eleven are molecular cloud-H II region complexes. The remaining three appear to be similar (perhaps younger) objects; they are strong in the far infrared, but have no visible H II regions. Enhancement of the lower satellite transition of CH is seen in most cases. CH was also detected in association with the Herbig B8-A2e star V380 Ori. This emission was the most intense of all the CH detections. An effort was made to find a maser transition for a carbon-bearing molecule in late-type stars. A search was made for rotational transitions in the HCN bending mode (first overtone at 89.1 GHz) and stretching mode (fundamental at 88.0 GHz) as well as the CH ground state lambda-doublet in carbon stars.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 91
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  • 105
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    Spectroscopy of the B-gamma line in the Galactic center (1981)
    In:  Other Sources
    Details
    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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  • 106
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    The 1980 June X-ray high state of Cygnus X-1 - Optical changes (1981)
    In:  Other Sources
    Details
    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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  • 107
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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.
    Keywords: ASTRONOMY
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  • 108
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    The Goddard program of gamma-ray transient astronomy (1981)
    In:  Other Sources
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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.
    Keywords: ASTRONOMY
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  • 109
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    Infrared spectrometer for Voyager (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Voyager IR investigation is described, which uses a Michelson interferometer in the 180-2500/cm range, and a single-channel radiometer for the visible and near-IR, sharing a 50-cm diameter telescope. Emphasis is placed on the differences between the Voyager and the previous designs, including reductions in the field of view and in the noise equivalent spectral radiance of the instrument. Attention is given to the optical layout, the electronics module, power supply placement, thermal control heaters and flash heaters, data reduction, and calibration. A sample spectrum of Jupiter is also discussed.
    Keywords: ASTRONOMY
    Type: Applied Optics; 19; May 1
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  • 110
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    Optical redshifts of 59 galaxies (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper presents the results of an observing program carried out to measure galaxy redshifts with the Cassegrain Digicon Spectrograph system on the McDonald Observatory 2.1 m Struve telescope. New redshift determinations are presented for 59 galaxies, obtained for emission line spectra by conventional wavelength determination techniques and for absorption line spectra by Fourier transform filtering and cross correlation techniques with respect to velocity standard spectra of NGC 3115 and NGC 4736. With respect to published redshifts for 29 galaxies, the new redshifts show a mean residual of -1 km/sec and rms residual of 49 km/sec, without apparent systematic trends, from -300 to +13,700 km/sec.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 85; Feb. 198
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  • 111
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    Mass loss from the central star of the planetary nebulae IC 3568 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Low resolution IUE spectra of IC 3568 show several stellar P Cygni features. A high resolution spectrum was obtained which shows a saturated N V lambda 1240 profile from which we find the terminal velocity of the tellar wind to be v = 1840 km/s. The P Cygni features due to C IV lambda 1549, O V lambda 1371 and N IV lambda 1719 are also observed. The unsaturated O V lambda 1371 line seems best for determination of the mass loss rate. It is found that the level of ionization in the stellar wind appears to increase outwards. The possible effects of such stellar winds from central stars on surrounding nebulae are discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 610-614
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  • 112
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    The peculiar, luminous early-type emission line stars of the Magellanic clouds: A preliminary taxonomy (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A sample of some 20 early type emission supergiants in the Magellanic clouds was observed with both the SWP and LWR low resolution mode of IUE. All stars have strong H-emission, some showing P-Cygni structure as well with HeI, HeII, FeII and other ions also showing strong emission. It is found that the stars fall into three distinct groups on the basis of the HeII/HeI and HeI/HI strengths: (1) HeII strong, HeI, HI; (2) HeII absent, HeI, HI strong; (3) HeI absent, HI, FeII, FeII, strong in addition to low excitation ions. The two most extreme emission line stars found in the Clouds S 134/LMC and S 18/SMC are discussed. Results for the 2200A feature in these supergiants, and evidence for shells around the most luminous stars in the clouds are also described.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 602-605
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  • 113
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    Magnetospheres and winds of the helium strong stars: Dependence on rotation (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Large aperture, low resolution spectra of 24 stars of types 05, 04, and 03 were obtained, and from these the energy distribution between 1200 and 3200 angstrom was derived in absolute units. The energies were combined with energies deduced from uvby and UBV photometry and corrected for interstellar extinction. Angular diameters and effective temperatures are also derived. The effective temperatures range from 24800K to 63000K. There is no correlation between effective temperature and spectral type or luminosity class for the early 0 stars. The size of the expected errors are also studied.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 589-592
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  • 114
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    The chromospheric rotation activity relation in late type close binary systems (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The IUE data on 36 late type close binary stars are presented. It is shown that the chromospheric and TR line fluxes increase with decreasing stellar rotation period, though not as rapidly as does the X-ray flux. There is an increasing dependence upon rotation with increasing line temperature. The data are consistent with the hypothesis that there exists a critical rotation rate, which depends on temperature, below which the emission flux is independent of rotation and above which it increases linearly with increasing angular velocity omega.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 566-569
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  • 115
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    Observations of the May 1979 outburst of Centaurus X-4 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The IUE spectra of the X-ray transient/X-ray burst source Cen X-4 at three intervals during the peak and decline of the May 1979 transient event were studied. The spectrum is characterized by a blue continuum and strong emission lines of N V lambda 1240, Si IV lambda 1398 and C IV lambda 1550. The origin of these emission components in the context of an X-ray dwarf nova model is investigated. It is suggested that an accretion disk plays a prominent role in the generation of the continuum emission and that X-ray heating of the accretion disk and the companion star may be important in the formation of the emission lines.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 558-562
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  • 116
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    Model fitting of the Algol binaries (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Energy distribution of the component stars of the Algol type semidetached binaries were studied by combining IUE low dispersion spectra with optical scans made with the same resolution. In most cases the flux distributions are matched by Kuruz model atmospheres with normal solar composition. Deviations from normal atmospheres which indicate a higher level of activity and interaction in the binaries are examined. Eclipse observations in U Cep and V356 Sgr reveal emission lines of the W serpentis type.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 538-541
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  • 117
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    Observations of mass accretion in binary stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results from high resolution observations of eight close binary stars (TX UMa, U CrB, CX Dra, TT Hya, AU Mon, KX And, HR 2142, and phi Per) are presented. Variable absorption lines, indicative of mass flow, are observed in all systems expect phi Per. Emission lines are seen in KX And and phi Per. Variable high ionization features (NV, SiIV, and CIV) are seen in TX UMa, UCrB, CX Dra, and AU Mon. The observations are modeled using the calculations of Lubow and Shu.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 534-537
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  • 118
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    Line-profile and continuum variations of the contact binary SV Centauri (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A total of five high and ten low dispersion UV spectra of the interacting contact binary SV Centauri obtained between 1979 and 1982 are analyzed. The low resolution observations cover the whole phase range, while a few selected phases were observed in high dispersion. The UV data were complemented with optical photometric and spectroscopic observations, in order to determine the tructure and absolute dimensions of the system. The profiles of prominent UV resonance and metastable lines undergo drastic changes with phase angle and time. Their overall appearance indicates relatively strong mass loss from the system, exhibiting pronounced variations of the stellar wind. The far UV continuum distribution suggests the presence of a luminous hot radiation source with maximum emission in the soft X-ray range, which is most apparently seen during the first quadrature phase, while it is weakest close to primary minimum. The case exchange and mass loss process as well as the evolutionary stage of SV Centauri are discussed.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 521-525
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  • 119
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    IUE spectroscopy, visible-band polarimetry, and radiometry of V641 Mon (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: This hot, double line, ellipsoidal variable member of NGC 2264 has been shown previously to be either a semi-detached or contact close binary. Low-resolution IUE spectra are best fitted to a Kurucz model atmosphere for very small (approximately 0.08 mag) E(B-V). The familiar interstellar absorption dip near lambda 2200 is apparently absent. A suitable model atmosphere can be fitted to the IUE fluxes, but flux excesses (compared to the model) appear for all the published U through L magnitudes. The spectrum of the B through L excess appears to follow a .0001 lambda dependence. It is shown that this cannot be interpreted as arising from another star fortuitously observed in the visible band or IR. Ground based polarization measures indicate V641 Mon to be a polarization variable. Previous and new V light curves show the amplitude of light variability itself to be variable by about a factor of 2. It is suggested that all these observed characteristics are best explained by postulating "third light" and identifying part of it with Rayleigh scattered starlight very near to the stars. From this same region there arise circumstellar absorptions which give rise to nontheoretical strengths for Si II and Si III lines.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 513-516
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  • 120
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    IUE observations of the 1981 outburst of nova Cr A (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Low dispersion spectrum observations are analyzed. The light curve of nova Cr A, indicating a moderately fast nova, is presented. Flux calibrated, merged spectrum graphs of April 21, 1981 and September 13, 1981 are presented, demonstrating very strong lines of Al and Si. Additional strong C, Ni, O, and Ne emission lines were identified. Emission lines due to highly ionized species such as Mg VII and Al Vl were observed for short times in May and June 1981. Preliminary analysis of spectra obtained 200 days after maximum indicate that the nebula is still in transition and has not yet reached the nebula state. An over abundance of N and Ne are suggested.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 478-481
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  • 121
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    Observations and analysis of the R Aquarii jet (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Ultraviolet, optical and radio observations of the symbiotic star R Aquarii are discussed in the light of the discovery of a bright radio and optical jet from this star. The star is probably a binary with a period of 44 years. The VLA maps of the jet reveal a protruding structure extending approximately 10 arc sec from the central radio source with a position angle virtually identical to that of the optical jet observed at Lick. The observations of R Aqr are interpreted as indicating the existence of an accretion disk around an unseen companion. The hot subdwarf has effective temperature approximately 65,000 K. It is suggested that the Mira primary and the hot secondary are in orbit around each other with a high eccentricity. At periastron the hot subdwarf accretes at super critical rates and a jet forms. It is difficult to understand how an accretion disk would have eclipsed the Mira in 1928-1935 and 1974-1980. The suppression of maximum light in these two periods is interpreted as due to a distortion of the Mira envelope at periastron by the tidal interaction with the secondary. The jet may help to explain the excitation of the R Aqr nebula. It is possible that R Aqr flared up as a nova approximately 1000 years ago forming the nebula.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 452-455
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  • 122
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    The high velocity symbiotic star AG Draconis after its 1980 outburst (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: High and low resolution spectra of AG Dra taken in 1981 are analyzed. The UV spectrum of AG Dra is characterized by prominent high ionization emission lines superimposed on a strong continuum. At high resolution, several intense absorption lines of interstellar origin are seen, in spite of the low interstellar extinction. A similar situation is displayed by the high galactic latitude sd0 stars. The radial velocity difference between the emission lines and the i.s. lines is about -105 Km/sec in agreement with the optical observations. The He II 1640 A line appears much stronger than in other symbiotic stars and suggests the presence of a hot source which is variable according to the activity of the star. The line also exhibits broad emission wings which could be formed in a rotating disk. The NV resonance doublet displays a P Cygni profile and is probably formed in a warm wind. Two components in the UV continuum are identified: a steep component dominating the far UV probably associated with the hot source, and a flatter continuum in the near UV which cannot be accounted for by f-f and f-b emission alone, but which is probably emitted by an optically thick region or disk.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 446-447
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  • 123
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    Ultraviolet spectra of R Coronae Borealis stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An analysis of the International Ultraviolet Explorer spectra of the R CrB-type variables R CrB, RY Sgr, XX Cam, and MV Sgr suggests that: (1) it should be possible to construct useful models for the atmospheres of these hydrogen deficient, carbon rich stars if present standards of metallic line blanketing are used; and (2) the observed wavelength dependence of the circumstellar extinction is primarily due to circumstellar grains.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 429-432
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  • 124
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    The UV emission line spectrum of NGC 6572 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Ultraviolet spectra of the medium excitation planetary nebula NGC 6572 were obtained with IUE both in the low and in the high resolution mode. These spectra reveal a superposition of emission lines arising in the expanding atmosphere of the central star, evidenced e.g., by their P Cygni profiles, and features arising in the planetary nebula proper. The latter were analyzed in order to determine C, N, O abundances.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 389-392
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  • 125
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    The violet interstellar medium associated with the Carina Nebula (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interstellar spectrum of HD 93205, an 03V star in the cluster Tr16, located inside the most active part of the Great Carina Nebula was analyzed using data extracted directly from raw IUE images. From the analysis of 67 lines of 25 atoms, ions and molecules, up to six discrete absorption components spanning a maximum velocity range of approximately 375 km 5/1 were identified. The component structure for different species is tabulated and sample absorption lines, indicating at the top the positions of the six components, labelled A to F are shown. Ion column densities appropriate to each component which can be resolved in at least one line were derived by constructing empirical curves of growth and by fitting the observations with corresponding theoretical absorption line profiles. The most important results concerning each component are discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 38-384
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  • 126
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    Small scale structure in the interstellar medium: Orion's threadbare cloak (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interstellar medium in the central portion of the Orion Cloak dynamical feature was examined for evidence of fine structure. Four stars in the Ori OB I association, HD 37017, 37468, 37479, and 37776 bracket the stars in the lower belt region that were studied previously. Two are members of the sigma Ori subcluster. A lower limit to the scale inhomogeneity can be set using these at 0.1 pc, while on a scale of about 10 pc, the high velocity component of the second spectrum ions shows optical depth variation of more than a factor of 5. Neutral lines do not display the high velocity component. Some preliminary abundances are also given.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 370-373
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  • 127
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    MAGELLAN: High resolution spectroscopy at FUV and EUV wavelengths (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The aim of ESA's MAGELLAN mission is to provide high resolution spectra of celestial sources down to sixteenth magnitude over the extreme ultraviolet wavelength range (between 50 and 140 nm). This range extends from studies of interstellar matter in the disc and halo of this and other galaxies, to stellar envelopes, hot and evolved stars, clusters, intergalactic matter, nuclei of galaxies, quasars, and, finally, planets and satellites. The instrument has a nonconventional optical design using only one reflecting surface; a high groove density concave grating collects the star light, diffracts it and focuses its spectrum into a bidimensional windowless detector operated in a photon counting mode. The slitless configuration provides the spectra of all the sources (point like and extended) in the field of view of the grating. This field of view is limited by a grid collimator to reduce the diffuse background, the stray light and the probability of overlapping spectra in crowded fields.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 347-354
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  • 128
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    Spectral anomalies in low dispersion SWP images (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Physical interpretation of IUE spectra obtained with the SWP camera may be significantly affected by artificial spectral features of several types. In low dispersion large aperture SWP exposures of sources with nominally featureless spectra, a spectral imprint which alters the shape of the continuum, several spurious "emission features" which recur at fixed locations on the camera target, and fixed pattern noise which can result in illusory emission and absorption features were identified. The anomalies appear in spectra extracted from line by line files generated by IUESIPS at all epochs, regardless of the ITF or rectification scheme used for processing.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 335-338
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  • 129
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    Faint object studies with IUE (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: To push IUE to the limit on faint sources, detector background contributions from the night sky, energetic particle events, detector flaws and calibration errors must be established. Multiple spectra of faint nebular filaments were intercompared with multiple spectra of sky background in a study of the Crab Nebula. Radiation hits dominate the background of any long exposure spectrum but bright spots of the detector can be misconstrued to be radiation hits, or spectral information. The spectra were normalized and then, on a pixel by pixel basis, average and median spectra were constructed. Four data sets (six SWP nebular, six SWP sky, six LWR nebular, and six LWR sky) were processed in parallel. A number of bright and faint background features remain, especially for SWP images. Several features could be misconstrued to be emission from a faint object.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 331-334
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  • 130
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    Global picture of a Be star (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An attempt is made to synthesize the observational material on Be stars into a empirical pattern of atmospheric structure. The sequence of atmospheric regions is developed and empirical-numerical estimates of location and structure of the regions are described. Inferences are drawn concerning the general stellar structure required to generate the nonthermal fluxes which produce the observed atmospheric pattern. In particular the atmospheric and subatmospheric origins of mass flux are addressed.
    Keywords: ASTRONOMY
    Type: NASA, Washington B Stars With and Without Emission Lines, Parts 1 and 2; p 409-451
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    An investigation of the neutral and ionized gas in M16 (1981)
    In:  Other Sources
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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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  • 132
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    On the variability of LSI+61 deg 303 (identical with GT 0236) (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Out of six long and six short wavelength observations, one spectrum exhibits a significant photometric variation: or approximately 20%. Interpreting the continuum as due to superposition of an early B main sequence star plus a gaseous component contributing at lambda 2000 A, the wavelength dependence of the variation suggests that it derives from the latter component. The data indicate that if the observed variation is phase dependent, a minimum should occur between phases 0.8 and 0.2. However, since the variation is observed in only one spectrum, it may well be erratic.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 615-618
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  • 133
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    Empirical atmospheric velocity patterns from combined IUE and visual observations: The Be similar stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The velocity pattern which panspectral observations of the Be stars suggest, and an outline of its extension via similar panspectral observations of the Be similar stars are summarized. The time dependent interaction between the stellar mass flux and the local environment produced jointly by the star itself and its original environment are emphasized.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 584-588
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  • 134
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    Mass loss at discrete velocities in Be stars: Evidence for non-radiatively driven wind (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The temporal behavior of the high velocity, relatively narrow absorption components in C IV, Si III, IV observed in the pole-one Be stars psi Ori, 66 Oph, and HR 4009 and what these observations contribute toward our understanding of the Be phenomenon are discussed. Ground based and X-ray data on these stars are compared as well as their UV differences with similarly active Be stars with larger projected rotational velocities.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 575-578
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  • 135
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    continuum and emission lines in eta Lyrae (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Integral photometric characteristics of beta Lyrae were redetermined using its brightest visual companion, the star HD 174664. It was attempted to separate the fluxes coming from the two components. The flux distributions are badly contaminated by the radiation of the circumstellar hydrogen. Peculiarities seem to be present in both components; in particular, the secondary star cannot be represented by an atmosphere with a unique effective temperature, and best represented by a thick disk.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 550-553
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  • 136
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    A recent time of minimum for and atmospheric-eclipse in the ultraviolet spectrum of the Wolf-Rayet eclipsing binary V444 Cygni (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The 1200-1900 angstrom region and fine error sensor observations in the optical for V444 Cyg were continuously observed. More than half of a primary minimum and almost a complete secondary minimum were observed. It is found that the time of minimum for the secondary eclipse is consistent with that for primary eclipse, and the ultraviolet times of minimum are consistent with the optical ones. The spectrum shows a considerable amount of phase dependence. The general shaps and depths of the light curves for the FES signal and the 1565-1900 angstrom continuum are similar to those for the blue continuum. The FES, however, detected an atmospheric eclipse in line absorption at about the phase the NIV absorption was strongest. It is suggested that there is a source of continuum absorption shortward of 1460 angstrom which exists throughout a large part of the extended atmosphere and which, by implication, must redden considerably the ultraviolet continuua of WN stars. A fairly high degree of ionization for the inner part of the WN star a atmosphere is implied.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 542-545
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  • 137
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    A search for cataclysmic binaries containing strongly magnetic white dwarfs (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The AM Herculis type binaries which contain accreting white dwarfs with surface magnetic fields of a few times 10 to the seventh power gauss were studied. If white dwarfs in cataclysmic binaries have a range of field strengths similar to that among single white dwarfs. AM Her like systems should exist with fields as high as 3 x 10 to the eighth power gauss. It is suggested that such objects will not have the strong optical polarization of the AM Her variables; however, they exhibit high harmonic cyclotron emission, making them spectacular UV sources. We made IUE observations of seven candidate cataclysmic variables selected for optical similarity to AM Her binaries. Although all seven objects were detected in the UV, none display unusually strong UV continua. It is suggested that the distribution of magnetic field strengths among single white dwarfs may be different from that among binaries.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 530-533
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  • 138
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    An ultraviolet investigation of the unusual eclipsing binary system FF AQR (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A series of seven low dispersion IUE exposures in ultraviolet and wavelength regions obtained on December 6, 1981 during the eclipse of the subdwarf, during egress, and out of eclipse is analyzed. These observations and the binary phase at which they were made are shown on a schematic representation of the V-band light curve obtained in 1975. The depth in V is 0.15 mag. The circles are IUE V magnitudes from FES measures obtained during the observing run. They indicate an eclipse depth some 0.05 mag lower than expected, possibly due to difficulties with the color term in the FES calibration. The eclipse depths of Dworetsky in U, B and V were assumed in the calculations.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 577-520
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  • 139
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    Pre-eclipse ultraviolet spectra of Epsilon Aurigae (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Existing high dispersion, long wavelength IUE, high dispersion long and short wavelength, and Balloon borne ultraviolet stellar spectrograph (BUSS) spectra providing a baseline measurement of the ultraviolet spectrum of the Epsilon Aurigae system before eclipse are reviewed. Plans for ultraviolet spectrum IUE observations during the 1982 to 1984 eclipse of Epsilon Aurigae are presented.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 505-508
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  • 140
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    The ultraviolet variability of T Cr B (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Preliminary results of the ultraviolet variability monitoring of the recurrent nova T Cr B are presented. The star has shown striking changes of the continuum (both shape and integrated luminosity) and of the emission lines since 1979, with a maximum activity in early 1981. In the same period the visual luminosity remained practically constant. The data being studied that the UV variability is due to changes in the physical structure of the accretion disk around the secondary.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 482-485
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  • 141
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    Cataclysmic variables: Disk characteristics from UV observations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Low dispersion IUE spectra of 3 cataclysmic variables (V442 Oph, V794 Aq1 and H2215-086) are discussed in terms of current disk models. The range of continuum fluxes, line emission and disk parameters of these three novalike systems are compared with past observations of dwarf novae at outburst and quiescence. Evidence of variability on orbital time scales is presented for V442 Oph and H2215-086.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 474-477
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  • 142
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    High velocity gas outflow from the nova-like variable LSI 55 deg -8 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Low and high dispersion International Ultraviolet Explorer observations and measurements of the optical brightness of LSI 55-8 taken on 5 December, 1981 are analyzed. The presence of the C IV resonance doublet showing a variable P Cygni type of profile with a blue shifted absorption component along with the blue shifted absorption features of the high temperature ions indicate the existence of outflowing hot plasma (i.e., a wind). An upper limit of the mass outflow rate was established from the shot wavelength edge of the C IV absorption. The normalized C IV profile is shown o be variable with the largest changes occurring in the relative strength and shape of the emission component. These changes appear to be systematic, and may be associated with the changing projection of the outflowing hot plasma against the disk as a function of orbital motion. LSI 55-8 demonstrates most of the spectral and photometric characteristics exhibited by the nova like, UX UMa type variables, as well as with the dwarf novae in outburst or standstill. The high accretion rate inferred from fitting the Williams theoretical disk model fluxes to IUE data support the hypothesis that LSI 55-8 and related nova like systems are in a state of prolonged outburst.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 465-469
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  • 143
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    IUE observations of dust albedo in nebulae (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The wavelength dependence of the effective albedo of the dust at several positions near the Hourglass region of M8 was determined. Accurate estimates of the contribution of the continuous gas emission can be made using the region 1400A to 1600A. The main uncertainty results from the peculiar extinction of the exciting star, Herschel 36, and the possibility that extinction between the star and the reflecting portions of the nebula exists and needs to be corrected for. The albedo for some planetaries such as NGC 6543 were also investigated. The main uncertainty here is estimating instrumental contributions to the scattering in observing these small objects.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 405-408
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  • 144
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    IUE observations of planetary nebulae and their central stars in the Magellanic Clouds (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The planetary nebulae LMC P40, SMC N2, and SMC N5 and their central stars were observed with IUE. The C abundances in the nebulae, compared with those in galactic planetaries, indicate that convective dredgeup of locally nucleosynthesized C has occurred. The progenitors of the nebulae were C stars at the theoretical upper luminosity threshold, thus such stars do occur as predicted, although none so bright have been found in the Clouds. The central stars of the nebulae have masses approximately 1 solar mass, luminosities approximately 40,000 solar luminosity, and radii approximately 0.7 solar radius; they have probably not yet reached their maximum luminosities. With M(subv) 19.1-19.8, they may be the visually faintest stars yet observed by UV spectroscopy. Clearly, it is not true that planetary nebulae nuclei all have masses M = (0.6 + or - 0.1) solar mass.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 397-400
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  • 145
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    High dispersion observations of selected regions in the Orion Nebula (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: High resolution spectral observations were made of several regions of the Orion Nebula near theta (2) Ori A using the IUE. The positions were selected using a moderate spatial resolution map from a previous low dispersion IUE survery of this section of the nebula. With the SWP and LWR cameras, 28 pectra were obtained of the bright bar, three Taylor-Munch cloudlets, and several surrounding locations. Emission lines of He, C, N, O, Mg, and Si allow a characterization of these cloudlets and of the gas in and around the bar. Small aperture observations provide radial velocity information for the ultraviolet emission of these features. These data show ionization variations from region to region and are suggestive of stellar wind interactions between the cloudlets and theta(2) Ori A.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 374-379
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  • 146
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    Highly ionized gas in the galactic halo (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The major results are summarized of a study of interstellar absorption in the halo which makes use primarily of IUE observations of a sample of 24 OB stars at z distances between 0.5 and approximately 3 kpc. These data, which cover a wide range of directions, are analysed together with other available results in order to investigate the distribution and physical conditions of highly ionized gas in the halo.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 363-368
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  • 147
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    The photometric performance of the IUE (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The scientific objectives and performance characteristics of a new astronomy mission referred to as the far ultraviolet spectroscopic explorer, or FUSE are being defined by team involving people experienced in instrumentation, observations, and theory in order to develop. mission and instrumental requirements that best meet the scientific needs. The team is intended to have a lifetime of about one year, ending with the submission of a report to NASA which could be used as the basis for an engineering design study. The principal objective of FUSE is to obtain astronomical spectra at wavelengths shorter than is possible with the Space Telescope.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 339-342
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  • 148
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    Bibliographical index of objects observed by IUE (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Six astronomical journals were searched and 343 papers describing studies using data obtained with the International Ultraviolet Explorer satellite were identified. From a review of these papers, the names of the astronomical objects discussed were recorded and compiled into a list of 2460 entries, along with each reference, and sorted by object name or catalogue number. This index enables a user to tell immediately where to find published papers describing IUE observation of the objects of interest to him.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 322-325
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  • 149
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    The IUE echelle blaze function (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An improved form for the echelle blaze function derived by Ake (1981) was used to study the apparent variation of grating constant K with order m for the long and short wavelength spectrographs. For the LWR camera, early images indicate that K should vary linearly with order. It is suggested that this represents a rotation of the observed blaze centers on the camera compared to a constant K=m lambda line. In four years of use, changes in sensitivity across the camera changed the observed blaze function, inducing a curvature in the K versus m relation. This curvature varies in time with variations in camera response. The SWP camera shows these effects to a lesser degree.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 318-321
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  • 150
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    The relevance of the IUE results on young stars for Earth's paleoatmosphere (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Using the latest IUE results for seven T Tauri stars, which are believed to represent the young Sun and a detailed photochemical chemical model of the paleoatmosphere, the vertical distribution of Oxygen and Ozone in the early atmosphere was calculated. The calculations indicate that the surface Oxygen mixing ratio is as much as six orders of magnitude larger than previously estimated, but appears low enough for the formation of amino acids via the Urey-Miller type of experiments. It is believed that the quantification of the oxygen level in the Earth's paleoatmosphere presented can reconcile the demands of both biological and geological considerations.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 293-296
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  • 151
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    High dispersion far ultraviolet spectra of cool stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Recent far ultraviolet high dispersion spectra of two cool supergiant stars, Beta Dra (G2 Ib) and Alpha Ori (M2 Iab) are examined in the context of current questions regarding stellar chromospheres, coronae and mass loss. These stars show very different outer atmosphere structure. Beta Dra has a geometrically thin transition region with bright emission lines of 100,000 K plasma that are red-shifted, indicating downflow in magnetic flux tubes. By contrast, Alpha Ori has a cool extended chromosphere and circumstellar envelope with large mass loss.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 259-262
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  • 152
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    Ultraviolet spectra of Herbig-Haro objects and of the environment of the Cohen-Schwartz star (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations in both spectral regions were used in order to determine the continuous energy distribution and the emission line fluxes for H-H 2. The continuous spectrum is similar to that in H-H 1 and F lambda increases rapidly towards shorter wavelengths. This statement is found to be qualitatively correct for all obvious choices of the ultraviolet extinction curve if we use the E(B-V) value determined by the use of the S II method. The origin of the continuum remains enigmatic. The emission line spectrum of H-H 2 shows an even somewhat higher degree of ionization than the spectrum of H-H 1, indicating an even larger discrepancy between ionization information from optical data and that contained in the UV spectra. The immediate environment of the Cohen-Schwartz star emits a continuous spectrum similar to that of a H-H-object but increasing even more steeply towards shorter wavelengths.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 223-226
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  • 153
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    Simultaneous multifrequency observations of BL Lac objects and violently variable quasars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Ultraviolet spectra simultaneous with radio, infrared, optical, and X-ray measurements were obtained for three BL Lac objects and one violently variable quasar during several epochs (0735+178, BL Lac, IZw-187, and 3C446). A feature common to these objects is that the radio-mm continuum must steepen in the far-infrared region in order to connect smoothly to the IR-UV continuum. This indicates that synchrotron emission becomes optically thick in the mm or far-infrared region. The continuum of 3C446 and BL Lac steepen quite rapidly between the IR and UV spectra with slopes near unity. The X-ray emission in BL Lac, 3C446, and 0735+178 has a different origin from the IR-UV radiation, probably from the inverse Compton process. However, the synchrotron radiation is the probable source of X-ray emission in the X-ray bright BL Lac object IZw-187. In IZw-187, most of the energy emerges in the UV - X-ray region, while for the other sources, most of the energy emerges in the far infrared region.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 197-200
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  • 154
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    IUE ultraviolet spectral atlas (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Low dispersion trailed spectra for a group of normal stars, with sample plot and flux tables, are presented. Exposure times are computed assuming 21.4 and 20.5 arcsec aperture lengths.
    Keywords: ASTRONOMY
    Type: ESA Ultraviolet Stellar Classification Classification; p 25-54
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  • 155
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    Chromospheres and coronae in the T Tauri stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Tauri stars exhibit strong far ultraviolet emission lines of C II, III, IV; OI; Si II, III; IV; and sometimes N V and He II. Surface fluxes of the lines for several T Tauri stars were computed, drawing upon both International Ultraviolet Explorer observations and published spectra. The surface fluxes are quite high. The FUV lines together account for 0.1% of the stellar luminosity. These results indicate the presence of active relatively dense chromospheres. The Tauri stars showing very strong visual emission spectra exhibit weakened high temperature FUV lines of C IV and N V, as well as He II which may be produced by X-rays. In the same stars, no X-ray emission was detected with Einstein. Among all the T Tauri stars the X-ray luminosities are deficient by factors of 100 to 1000 compared to the FUV lines. It is argued that the X-ray flux has not been heavily absorbed by circumstellar gas, as has been previously suggested, but that the X-rays are truly underluminous, perhaps due to the stellar wind. It is suggested that the birth and development of the chromosphere and corona may be occurring during the T Tauri stage of protostellar evolution.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 456-459
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  • 156
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    Intensity changes in the UV spectrum of Beta Cephei (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Fifty eight short wavelength International Ultraviolet Explorer spectra were taken over a 152 day period. Variations in the absorption lines of C IV (1550 A), Si IV (1393 and 1404 A) and N V (1239 and 1243 A) and a Cr III feature (1208 to 1211 A) were observed. A data reduction technique was developed in order to compare the changes in the equivalent widths of these absorption lines. Periods were determined by least squares fit to a sinusoid using several combinations of the data. In one case eighteen spectra for each ion taken at approximately one day intervals were used; in another, all 58 measurements of each were used; and in a third all measurements from all the ions wee combined. Using both variable metric and interactive algorithms it was determined that for all combinations mentioned a period of 6.10 + or - .06 days is the best fit to the vector of equivalent widths versus time. No other period, with or without the 6.10 day period removed from the data, was found. Analysis of the Cr III feature near 1210 A gives the same period as the others, but in antiphase.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 442-445
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  • 157
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    Chromospheres of classical Cepheids (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The International Ultraviolet Explorer spectra of five classical Cepheids were obtained in the short and the long wavelength regions at low dispersion, curves and emission line strengths were obtained from the low resolution spectra. The amplitudes of the light curves increase with decreasing wavelength except around 1550 A where the amplitude is surprisingly small. The emission line fluxes behave differently in the various stars and it appears that bumps in the ultraviolet light curves are related to the behavior of the chromospheres. However, the strengths of the emission lines are roughly comparable to nonvariable stars of similar temperature and luminosity. The high resolution spectra were used to study the fluxes of the emission from the Mg II h and k lines. It is found that the emission components come and go during the cycles and the behavior differs from one star to another, with generally stronger and more persistent emission at longer periods. This is compared with the times of appearance of the Ca II H and K emission features and provides insight into the way in which the chromosphere reacts to shock waves generated by the pulsation of the star.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 439-441
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  • 158
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    The peculiar UV extinction of Herschel 36 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The differential extinction curve of Herschel 36 was determined from International Ultraviolet Explorer data. It is quite unusual, characterized by a distinct 2200 A peak with a very low far blue end at 5 to 7 mu to the -1 power. The star appears to be an extreme member of the group Savage drew attention to, previously consisting only of theta Ori, NU Ori, sigma Sco, and rho Oph. It appears that multiple scattering effects are needed to explain the observations.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 413-415
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  • 159
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    CNO abundances in H II regions of the Magellanic clouds and the galaxy with implications regarding the nucleosynthesis of the CNO element group (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Final abundance results of IUE observations of the UV spectra of three H II regions in the Small Magellanic Cloud and four H II regions in the Large Magellanic Cloud are presented. Calculated yields of carbon and oxygen derived are y(C)=.00063 and y(O)=.0016. The nucleosynthetic origin of nitrogen was evaluated as being predominantly a secondary element produced from carbon as its seed. Plotting log N/C versus log C/H yielded the rather unexpected result that log N/C decreases with lo C/H over the SMC-LMC-Orion range. The cause of this relationship is discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 385-388
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    The far ultraviolet spectroscopic explorer (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The scientific objectives and performance characteristics of a new astronomy mission referred to as the far ultraviolet spectroscopic explorer, or FUSE are being defined by a team involving people experienced instrumental requirements that best meet the scientific needs. The team is intended to have a lifetime of about one year, ending with the submission of a report to NASA which could be used as the basis for an engineering design study. The principal objective of FUSE is to obtain astronomical spectra at wavelengths shorter than is possible with the Space Telescope.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 345-346
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    Distribution of gas in the halo of the galaxy (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results are presented from a high-resolution, ultraviolet study of interstellar gas situated away from the plane of the Milky Way Galaxy, using the nuclei of Seyfert galaxies Mkn 509 and F9 as background probes. In these directions, low-velocity, galactic gas were detected as well as two extragalactic clouds, one probably associated with the Magellanic Stream and the other with Mkn 509. These data were combined with results from other lines of sight to show that the ultraviolet species extend about 10 kpc from the plane, assuming the high-latitude gas corotates with the galactic disk. Complimentary observations of the optical Ca II and Na I species suggests that these do not extend as far - perhaps 2 to 3 kpc from the plane. Further, the exceedingly complex velocity structure found only in Magellanic Cloud directions suggests that these sight-lines are not typical of high-latitude gas in general.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 359-362
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  • 162
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    IUE data reduction: Wavelength determinations and line identifications using a VAX/750 computer (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A fully automated, interactive system for determining the wavelengths of features in extracted IUE spectra is described. Wavelengths are recorded from video displays of expanded plots of individual orders using a movable cursor, and then corrected for IUE wavelength scale errors. The estimated accuracy of an individual wavelength in the final tabulation is 0.050 A. Such lists are ideally suited for line identification work using the method of wavelength coincidence statistics (WCS). The results of WCS studies of the ultraviolet spectra of the chemically peculiar (CP) stars iota Coronae Borealis and kappa Camcri. Aside from confirming a number of previously reported aspects of the abundance patterns in these stars, the searches produced some interesting, new discoveries, notably the presence of Hf in the spectrum of kappa Camcri. The implications of this work for theories designed to account for anomalous abundances in chemically peculiar stars are discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 326-330
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  • 163
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    On the correlation between chromospheric and coronal emission (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is shown that with increasing stellar activity the emission of the transition region and corona increases faster than the emission of the chromosphere. It is also explained why the pressure of the transition region increases with increasing stellar activity. Further, it is shown that this relation is a necessary requirement for the global stability of the chromosphere/transition region/corona system.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 268-272
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  • 164
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    The ultraviolet spectra of R and N type stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Low dispersion long wave radiation spectra of three early N-type carbon stars (BL Orionis, TX Piscium and T Indi) obtained with the IUE are discussed. N-star spectra were compared with IUE observations of late M-type stars and several differences were noted. The Mg II and C II chromospheric emission lines reported are the first convincing detection of a 10,000-20,000 K chromosphere in the N stars.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 255-258
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  • 165
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    Discrepant asymmetry stars: The role of unsteady magnetic flux loops in the atmospheres of late-type giant stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A number of spectroscopic peculiarities of K giants and other stars which lie in a wedge in the HR diagram are discussed. These peculiarities can be understood in terms of unsteady magnetic flux loops emerging into the stellar atmosphere from beneath the surface.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 235-238
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  • 166
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    An IUE survey of the Hyades star cluster (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: To date 11 of the brightest X-Ray stars (F-K dwarfs) in the Hyades have been observed with the IUE satellite with the short wavelength spectrograph. The IUE results and the X-Ray observations from the Hyades survey with the Einstein Observatory were combined. The differential emission measure function was estimated for each of the 7 stars which showed evidence of emission lines. Constraints on stellar atmospheric parameters (chromospheric pressure, coronal temperature and filling factor were derived. The implications of these results in the context of loop models for the corona and transition region (TR) of these stars are discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 239-242
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  • 167
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    Synoptic studies of chromospheric variability in F - K dwarfs with the IUE (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Time-sequential series of IUE spectra for ten F, G and K dwarfs were obtained in 1980 and 1981 to study the rotational dependence of chromospheric flux in the ultraviolet. An interactive computational method using unbiased estimators was developed to measure emission line fluxes free of arbitrary judgement concerning the behavior of the underlying spectrum and shapes of the line profiles. Due to the limited number of observational samples per star, we have used special techniques to analyze the sparsely and anharmonically sampled emission line flux data. Two different autocorrelation measures were computed for each emission line as a function of temporal frequency. Examples and results of this analysis now in progress are given for several stars.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 227-230
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  • 168
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    Changes in the UV spectrum of HD 4174 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is noted that the symbiotic-like object HD 4174 (EG And) exhibits the optical spectrum of an M2 giant star, but also shows Balmer and nebular line emission. The first UV spectrum showed an intense far UV emission line spectrum typical of many symbiotic stars. A 470 day binary or pulsation period for this system, based on the changing strength and velocity of the H alpha emission. Preliminary indications are that the H alpha and far UV continuum are eclipsed near phase 0.6 (at maximum H alpha redshift), but that the correlation for the emission lines remains unclear and requires additional observations.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 219-222
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    Multifrequency observations of the quasar 1156+295 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The recent outburst in the quasar 1156+295 was discovered in the course of optical monitoring made in preparation for IUE observations in April 1981. Short and long wavelength spectra were obtained on three occasions when the object was very bright, and which were separated in time by intervals of 4 and 60 days. The UV continuum in all cases is a steeply falling power law, with slope close to -2.0. No spectral features are apparent in the UV. Closely simultaneous observations were made by our collaborators at radio, infrared, and optical frequencies. The continuum is less steep at optical and infrared frequencies, and the overall spectra show little change in shape with time.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 201-204
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    Four years of IUE research on clumpy irregular galaxies (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: During the first four years of IUE operations seven shifts were used to observe 4 clumpy irregular galaxies: Markarian 7, 8, 297, and 325. All spectra were obtained at low resolution in both short and long wavelength, with exposure time ranging from half to a full shift. The IUE spectra of clumpy irregular galaxies show that the clumps contain a very large number of early O and B type stars, with a large number of supergiants with respect to the main sequence stars. Possibly Wolf-Rayet stars and massive objects of the type of R 136a could also contribute to the clump luminosity. On the average, each clump radiates in the UV 100 times more than 30 Dor. On the other end the liner dimension of a clump is not much larger than the one of 30 Dor.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 156-159
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  • 171
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    IUE observations of symbiotic stars (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The main photometric and spectroscopic characteristics in the ultraviolet and visual range of the most extensively studied symbiotic stars are reviewed. The main data obtained with IUE concern: (1) the determination of the shape of the UV continuum, which, in some cases, proves without doubt the presence of a hot companion; and the determination of the interstellar extinction by means of the lambda 2200 feature; (2) the measurement of emission lines, which enables us to derive the electron temperature and density of the circumstellar envelope, and, taken together with those lines observed in the visual, give more complete information on which spectroscopic mechanisms operate in the envelope; (3) the observation of absorption lines in the UV, which are present in just a few cases.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 89-101
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  • 172
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    Ultraviolet observations of interstellar dust (1982)
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    Publication Date: 2011-08-18
    Description: A large fraction of astronomical observations in the UV are affected by extinction due to interstellar dust in the line of sight. The shape of the extinction curve varies markedly around the sky, especially in regions of nebulosity such as the Orion Nebula. The variations of the shape provide clues to the nature of the dust. Additional insight into the physical properties of dust can be obtained from reflected UV starlight as observed in NGC7023 by IUE and in the faint arms of M101 as photographed by a sounding rocket.
    Keywords: ASTRONOMY
    Type: Advan. in Ultraviolet Astron.; p 68-79
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  • 173
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    The Sixth Catalogue of galactic Wolf-Rayet stars, their past and present (1981)
    In:  Other Sources
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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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  • 174
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    Observations of faint Haro galaxies (1981)
    In:  Other Sources
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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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  • 175
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    Reduction of astrographic catalogues (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An automatic program for the reduction of overlapping Carte du Ciel plates is described. The projection and transformation equations are given and the RAA subprogram flow is outlined. The program was applied to two different sets of data, namely to nine overlapping plates of the Cape Zone of the CdC, and to fifteen plates taken with the CIDA-refractor of the open cluster Tr10.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 99-104
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  • 176
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    Obtaining accurate comet positions despite some inaccurate catalog stars (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: From an astrographic negative a grid is determined from measurement of all the reference stars and using their catalog positions, and other grids from selections of reference stars. These grids are determined from many stars, and individual stars will have errors with respect to the grid. There are ways to identify stars X that are not at their cataloged position: (1) determine the focal length of the telescope from the measurements of each pair of stars and look for discordant results; (2) stars X are several arcseconds off the grid, and the other stars fit better when stars X do not help determine the grid; and (3) the grid is stretched or distorted to include the stars X. Fifteen to twenty percent of the stars in the S.A.O. catalog are 1.5 seconds or more off their catalog positions. An interactive session with a computer can find and eliminate these errant stars and result in more accurate comet positions.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 96-98
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    Desired characteristics of catalogs for cometary astrometry (1984)
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    Publication Date: 2011-08-19
    Description: Reference star catalogs for cometary astrometry have to provide an all-sky coverage with suitable stellar density and limiting magnitude on a fundamental coordinate system. A general catalog meeting all these requirements will not be available for a foreseen timescale. The suitability of various existing catalogs for cometary astrometry is discussed.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 87-92
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  • 178
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    The astrometry network of observers in USSR (1984)
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    Publication Date: 2011-08-19
    Description: A list of observatories included in the Soviet Astrometry Network is given. Some aspects of Astrometry Network activity are discussed. The Comet Halley star catalog is outlined.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 76-83
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  • 179
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    The IHW reference star catalogs for Comets Halley and Giocobini-Zinner (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The general categories of catalogs are observed and compiled. Observed catalogs are tabulations of positions determined with a single instrument (transit circle or astrograph) at a single location with a single approximate mean epoch. Compiled catalogs are produced from a combination of observed catalogs and have the advantage of many more observations per star. In addition, catalogs may be classified according to their density and type of instrument used to produce them. The specific catalogs that should be used for Halley's Comet and Giaobini-Zinner Comet are described.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 93-95
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  • 180
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    The astrometry network of observers in Japan (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The astrometric network of observers and the main telescopes for professional and amateur astronomers in Japan and their availability for the International Halley Watch (IHW) are described.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astometry; p 74-75
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    The astrometry network of observers in China (1984)
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    Publication Date: 2011-08-19
    Description: In China, the Purple Mountain Observatory (32 deg. 04 min. N and 118 deg. 49 min. E), the Shanghai Observatory (31 deg 06 min N and 121 deg 11 min E), and the Qingdao Station (36 deg 05 min N and 120 deg 19 min E) will take part in the astrometry of Halley's Comet. The astrometric work together with the instrumentation used, is given.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 71-73
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    The astrometry programme at Mt. John Observatory (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The comet (and minor planet) astrometry program uses one of two 0.6 meter (24 in.) Cassegrain telescopes at Mt. John University Observatory. For astrometric photographs of comets and minor planets a simple guide probe camera is attached to the Cassegrain. Frequently the Cassegrain field does not include sufficient cataloged stars for a satisfactory reduction. In these cases the comet position is transferred to an astrograph plate. Ephemeris data are calculated to the tenth of a day nearest the meridian transit of the object or for dusk or dawn twilight for low objects. Star measurement and identification are checked by reducing positions of cataloged stars.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 66-70
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    Problems and procedures of cometary astometry (1984)
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    Publication Date: 2011-08-19
    Description: Photography of comets or asteroids for the purpose of astrometry requires consideration of a few details not met with in other astronomical problems. In the general case the object has a substantial non-sidereal motion and the decision must be made whether to track on the fiducial stars or on the object. The best method for introducing the required image motion compensation to the detector will depend on the focal plane facilities. Measurement of elongated images and the problems involved are discussed.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 58-65
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    Kitt Peak measurements of P/Halley positions (1984)
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    Publication Date: 2011-08-19
    Description: Techniques used for the acquisition and reduction of imaging data for astrometric positions of comet Halley at Kitt Peak National Observatory are described. These techniques are applicable to the comet while it is fainter than magnitude V approximately 21. They yield positions that are uncertain by + or - 0.9 arcsec. The reliability and consistency of the positions already derived could be improved by as much as a factor of four in a more ambitious astrometric program.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 48-57
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  • 185
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    Astrometric plates obtained at the primary focus of large aperture reflectors (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Coma, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 45-47
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    Cometary astrometry with Schmidt cameras (1984)
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    Publication Date: 2011-08-19
    Description: A great many of the professional comet discoveries are made using wide field Schmidt telescopes. In particular the Palomar Schmidt, the ESO Schmidt in Chile and the UK Schmidt at Siding Spring Observatory in Australia. The wide field of view and fast f ratio are two of the distinctive features of this design which make it attractive for comet work. The techniques described refer to those in current use on the UK Schmidt. However in large part the methods described may be applied quite widely.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 34-40
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    Experiments to test theoretical models of the polarization of light by rough surfaces (1984)
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    Publication Date: 2011-08-18
    Description: A number of attempts have been made to provide theoretical models of the physical processes involved in the polarization of light scattered by a rough surface, such as the regolith of an atmosphereless planet. Some laboratory experiments designed to test different aspects of these models are described. It is concluded that double Fresnel reflection is usually the dominant process in producing negative polarization, but that diffraction effects may play a significant part in double events involving small-scale surface features.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 89-112
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  • 188
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    Comet Halley ephemeris uncertainties in 1985-1986 (1983)
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    Publication Date: 2011-08-18
    Description: For the planned flyby missions to Comet Halley in March 1986, the comet's ephemeris uncertainties completely dominate the spacecraft-comet miss distance. In an effort to determine realistic Comet Halley ephemeris uncertainties, a statistical covariance analysis was conducted using the actual data in 1909-1910-1911 and simulated data in 1984-1985-1986. In 1985-1986, Comet Halley's ephemeris uncertainties are very sensitive to the comet's orbital position, the optical data noise, data schedule, and whether or not the old data is included in the orbital solutions. The comet's ephemeris uncertainties in March 1986 are relatively insensitive to reasonable center of light/center of mass offsets and also to possible radar data taken in late November 1985. Accurate Space Telescope observations made in early March 1986 might significantly improve upon the comet's position uncertainties for the various intercepting spacecraft.
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    Dust particles in the anomalous tail of Comet Kohoutek (1973 XII) (1983)
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    Publication Date: 2011-08-18
    Description: Intermediate results from theoretical models of the anomalous spikelike dust distribution observed in the tail of Comet Kohoutek using the Skylab white-light coronograph on December 28.996, 1973, are reported. The time evolution is studied using the model of Finson and Probstein (1968) and assuming power-law variation of the dust-production rate and the particle-size distribution. Brightness profiles are calculated and presented graphically for comparison with those derived from the observation photograph: the model predicts a longer duration of the spike phenomenon than was observed. It is shown qualitatively that this discrepancy can be removed by introducing a finite dust-emission velocity (e.g., 1 m/s) into the model.
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  • 190
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    Cometary nucleus and active regions (1983)
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    Publication Date: 2011-08-18
    Description: On the basis of the icy-conglomerate model of cometary nuclei, various observations demonstrate the 'spotted' nature of many or most nuclei; i.e., regions of unusual activity, either high or low. Rotation periods, spin axes, and even precession of the axes have been determined. Narrow dust jets near the nuclei of some bright comets require that small sources be embedded in larger active areas. Certain evidence suggests that very dusty areas and very dusty comets may be less active, respectively, than surrounding areas or other comets.
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    Cryogenic telescope on the Infrared Astronomical Satellite (IRAS) (1984)
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    Publication Date: 2011-08-18
    Description: The Infrared Astronomical Satellite (IRAS) has completed an unbiased all-sky survey at wavelengths from 10 to 100 microns. The design and performance of the focal plane array is described with emphasis on in-orbit measurements of the sensitivity and stability. In the four broad spectral bands centered at 12, 25, 60, and 100 microns, the system noise equivalent flux density (NEFD) values are in Jy/(Square root of Hz), 0.03, 0.025, 0.046, and 0.21, respectively (Jansky = 10 to the -26th W/sq m/Hz). For point sources, a single scan at the survey rate of 3.8 arcmin/s yields limiting flux densities at the 3-sigma confidence level of 0.36, 0.30, 0.39, and 1.2 Jy. The dc stability of the junction field effect transistor (JFET) amplifiers and the excellent off-axis rejection of the telescope permit total flux measurements of extended infrared emission at levels below 6,000,000 Jy/sr. Response of the extrinsic silicon and germanium photo-detectors to ionizing radiation is described.
    Keywords: ASTRONOMY
    Type: Optical Engineering (ISSN 0091-3286); 23; 122-127
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  • 192
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    Preliminary scientific results from the first six months of the Infrared Astronomical Satellite (IRAS) (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Infrared Astronomical Satellite (IRAS) was successfully launched on January 25, 1983. This paper presents results based on analysis of early scientific data returned from IRAS. Among the early results of IRAS are the discovery of comet IRAS-Araki-Alcock, evidence for a shell of large particles around the nearby bright star Vega, detection of stars in the process of formation, and detection of many infrared bright galaxies. These early results demonstrate that the IRAS data will be a treasure chest for astronomers for years to come.
    Keywords: ASTRONOMY
    Type: Optical Engineering (ISSN 0091-3286); 23; 128-130
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  • 193
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    Regions of stability of asteroids (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Using Hill's modified stability criterion, regions of orbital elements are established for conditions of stability. The model of the three-dimensional restricted problem of three bodies is used with the sun and Jupiter as the primaries. Four different cases are studied: direct and retrograde, outside and inside asteroidal orbits. The directions of the asteroidal orbits refer to the synodical reference frame and the positions refer to Jupiter's orbit. The orbital parameters of the asteroids are the semi-major axis (a), the eccentricity (e), and the inclination from Jupiter's orbital plane (i). The argument of the perihelion and the longitude of the ascending node are fixed at Omega = omega = 90 deg and the time of perihelion passage is T = 0 for all orbits.
    Keywords: ASTRONOMY
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  • 194
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    The photometric method of detecting other planetary systems (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Rosenblatt (1971) has conducted an investigation regarding the use of photometric techniques to detect other planetary systems by searching for changes in starlight caused by the transit of a planet. The obtained results suggest that neither the intrinsic variation of the starlight nor the transmission fluctuations in the terrestrial atmosphere would prevent detection of planets as small as Mars with telescope apertures of 40 to 60 cm. The present investigation shows that Rosenblatt's results are too optimistic even for present-day differential photometric techniques. However, it appears that the detection of planets at least one-third the size of Jupiter is feasible, if a photometer with the required precision can be developed, taking into account the availability of a wide-angle telescope with a 1- to 2-m aperture.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 58; 121-134
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  • 195
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    The JPL 'long ephemeris', DE102/LE51 (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A number of applications exist in astronomical research for planetary and lunar ephemerides covering an extended length of time. This paper discusses such a set of ephemerides, DE102/LE51, produced at JPL, covering the time 1411 B.C. to 3001 A.D. The ephemerides are dynamically self-consistent, in that the equations of motion were integrated simultaneously. They also represent the most accurately known positions covering such a time span. They have already been used by a number of different users in a variety of different applications.
    Keywords: ASTRONOMY
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  • 196
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    The S201 far-ultraviolet imaging survey. III - A field in Sagittarius (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Far-ultraviolet imagery of a 20 deg diameter field in Sagittarius, centered near (1950) R.A. 18 h 34 m, decl. -30 deg 25 arcmin, was obtained by the S201 far-ultraviolet camera during the Apollo 16 mission. In a 10-minute exposure covering the 1250-1600 A wavelength range, 1034 star images are detectable, with a limiting ultraviolet magnitude of about 10. Most of these objects are identified with early-type stars listed in the Smithsonian Astrophysical Observatory Star Catalog, the Catalog of Stellar Identifications, or both, but 203 objects remain unidentified or are identified with late-type stars. The photometric measurements appear to be in reasonable agreement with those of the International Ultraviolet Explorer for stars in common, and with expectations for A0 stars. A detailed photometric study was made of the Messier 8 region, and it is concluded that dust-scattered starlight contributes about half of the total radiation observed from the central region of M8.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 55; 101-125
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  • 197
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    Angular momentum drain - A mechanism for despinning asteroids (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The new mechanism of angular momentum drain is proposed to account for the relatively slow rotation rates of intermediate-sized asteroids. Impact ejecta on a spinning body preferentially escape in the direction of rotation, systematically draining away spin angular momentum and leading to the counterintuitive result that collisions can reduce the spin of midsized objects. The existing theory of asteroid rotation is reviewed, and the escape of ejecta from hypervelocity impacts on bodies of different sizes and physical properties is described. The effect of this mass loss on asteroidal rotation is calculated and shown to be a significant brake on the spins of intermediate-sized asteroids. Finally, this new process is incorporated in a revised theory of collisional evolution, its predictions are compared with observational data, and its applications are discussed.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 57; 464-476
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  • 198
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    The motion of the earth-moon system in modern tabular ephemerides. II - Inertial motion, mean longitude of the sun, and general precession in longitude (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Properties of astronomical time scales (ET and UT) are considered, with particular emphasis on correctly determining of-date longitude as the sum of inertial mean longitude of the sun relative to the mean equinox of a fixed epoch (1950.0), and the general precession in longitude accumulated since the epoch. The inertial mean longitude and motion (relative to the mean equinox) are derived from tabular ephemerides such as the Jet Propulsion Laboratories' DE 102 and DE 96, by comparisons with subroutines based on Newcomb's perturbation theory. An unresolved inconsistency of approximately 1 second per century among the mean inertial motion of DE 102, IAU precession speed (1976), and the classical Newcomb of-date mean motion is found. Interpretation difficulties arising from the use of different systems of Ephemeris Time are also discussed.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 130; 2, Ja
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  • 199
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    Very large array observations of Jupiter's nonthermal radiation (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The VLA has been used at 18 and 20 cm to obtain observational data on Jupiter at all rotational aspects in all four Stokes parameters, yielding maps of the total, linearly polarized and circularly polarized intensity with a resolution of 0.25 Jupiter radii. These maps reveal such previously undetected phenomena as an emission feature close to the planetary surface north and south of each of the two main radiation peaks. The emission from 1.8 to about 3 Jupiter radii from the planet's center is sharply confined to the magnetic equator.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 54; 405-419
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  • 200
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    Dynamical evolution of the Oort cometary cloud (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The dynamical evolution of comets in the Oort cloud under the influence of stellar perturbations has been modeled using Monte Carlo techniques. It is shown that the cloud has been depleted over the history of the solar system. Comets are lost from the cloud by direct ejection due to close stellar encounters, diffusion of aphelia to distances beyond the sun's sphere of influence, or diffusion of perihelia into the planetary region where Jupiter and Saturn perturbations either eject them on hyperbolic trajectories or capture them to short-period orbits. The population of the cloud is estimated to be 1.0 - 1.5 x 10 to the 12th comets and the total mass is on the order of 1.9 earth masses. In addition to random passing stars, less frequent encounters with giant molecular clouds may play a significant role in randomizing the orbits of comets in the cloud and reducing the effective radius of the sun's sphere of influence.
    Keywords: ASTRONOMY
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