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  • Cell & Developmental Biology  (1.611)
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  • ASTRONOMY
  • 1985-1989  (1.799)
  • 1980-1984  (1.217)
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  • 1987  (1.799)
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  • 1985-1989  (1.799)
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  • 1
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    Palomar-Leiden minor planets - Proper elements, frequency distributions, belt boundaries, and family memberships (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Tabulations are presented for the proper elements of 1227 higher accuracy orbits of faint minor planets encompassing earth and deep Mars crossers, Trojans, and Hildas. The distribution of the closest approach distance to Mars drops off sharply near zero, while that for Jupiter vanishes near 1.1 AU; it is suggested that Mars and Jupiter have caused these boundaries, so that the asteroid belt must have been larger early in the solar system's history. Some 3.5 percent of the sample, primarily shallow crossers, can impact Mars; the fortuitous alignments required for impact occur with near-simultaneity for these objects, so that they will episodically bombard Mars.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 72; 276-303
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  • 2
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    Ground-based infrared observations of variable IRAS sources as candidates for late asymptotic giant branch stars (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Analysis of the color distribution of OH/IR stars and IRAS low-resolution spectra class 30 objects suggests the presence of a well-defined evolutionary sequence which is populated by late asymptotic giant branch (LAGB) stars. The paper reports ground-based identification and infrared photometry of 10 candidates of news LAGB stars. None of the selected sources are found to have optical counterparts, and eight of the 10 show a strong 10-micron silicate absorption feature. It is suggested that these stars represent an invisible extension of extreme Mira variables and are some of the most evolved stars observed to date.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 321; 975-983
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  • 3
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    Fourier removal of stripe artifacts in IRAS images (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: By working in the Fourier plane, approximate removal of stripe artifacts in IRAS images can be effected. The image of interest is smoothed and subtracted from the original, giving the high-spatial-frequency part. This 'filtered' image is then clipped to remove point sources and then Fourier transformed. Subtracting the Fourier components contributing to the stripes in this image from the Fourier transform of the original and transforming back to the image plane yields substantial removal of the stripes.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 94; 1092-109
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  • 4
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    Identification of a constellation from a position (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A table is presented which permits rapid determination of the constellation in which an object is located from its 1875.0 position. Directions for accessing and using the table are given. The historical background to the table's development is briefly stated.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99
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  • 5
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    Radar astrometry of near-earth asteroids (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An uncertainty analysis is conducted for four asteroids with different optical and radar observation histories in order to ascertain the degree to which near-earth asteroid ephemerides can be improved by means of radar observations. For any given set of optical and radar observations and their associated errors, the angular and earth-asteroid distance uncertainties are calculated as functions of time through 2001. The radar data furnished only a small absolute improvement in such cases as that of 1627 Ivar, where a long history of optical astrometric data exists, but dramatic reductions in ephemeris uncertainties are obtainable for asteroids having only short optical data histories.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 94; 189-200
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  • 6
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    The multichannel astrometric photometer and atmospheric limitations in the measurement of relative positions (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The operational Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric program is the culmination of a decade of design and development effort. A detailed description of the system and its related software is followed by analysis of data acquired in four stellar regions. The study indicates an accuracy (in the sense of conformity to the best model), per night, for stars of the eighth magnitude or brighter, of 0.003 arcsec or better. These data points each have approximately twice the precision of the annual normal points obtained in our photographic program. Accuracy is shown to depend on: (1) the photon-count rate of the target star (it follows that the number of photons from the reference frame is also in important factor), (2) the duration of the observation, (3) the angular size of the reference frame, and (4) the quality of the astronomical seeing. Since (4) and, to a lesser extent, (1) involve the atmospheric characteristics at the time of observation, the probable performance at more favorable sites is discussed briefly.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 94; 213-224
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  • 7
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    GUST86 - An analytical ephemeris of the Uranian satellites (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The General Uranus Satellite Theory GUST (Laskar, 1986) is used for the construction of an analytical ephemeris for the Uranian satellites. The theory is fitted against earth-based observations from 1911 to 1986, and all radio and optical data obtained during Voyager encounter with Uranus. Earth-based observations alone allow the determination of masses which are within 15 percent of the values determined by the Uranus flyby. The analysis of all the observations confirm the values of the masses obtained during the encounter (Stone and Miner, 1986) and give a complete set of dynamical parameters for the analytical theory. An analytical ephemeris, GUST86, with an estimated precision of about 100 km with respect to Uranus is obtained.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 188; 1, De
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  • 8
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    All-sky monitors for X-ray astronomy (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The rationale for a semipermanent all-sky X-ray monitor and a variety of options for its implementation are discussed. It is concluded that the Space Station offers an excellent opportunity for hosting such a monitor, and that a set of pinhole cameras can be configured to provide an effective and economical monitor system. A baseline of six independent pinhole modules, each of which requires approximately 1 cu ft, 30 pounds, 2 W and 100 bits per second, can provide full sky coverage with scientifically interesting sensitivities. No other resources or special accommodation (such as detailed alignment registration, time-tagging, or on-orbit servicing) would be required. The baseline system can locate bright sources to a few arcmin and can simultaneously measure each of the several hundred sources in the sky brighter than a few thousandths the intensity of the Crab nebula every day for decades.
    Schlagwort(e): ASTRONOMY
    Materialart: Space Science Reviews (ISSN 0038-6308); 45; 3-4,
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  • 9
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    The MIT spectroscopy investigations on AXAF and the study of supernova remnants (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The MIT High Resolution X-Ray Spectroscopy experiment on the AXAF, which will study physical conditions in celestial sources by means of detailed measurements of emission and absorption features in their spectra, involves two complementary dispersive instruments: Bragg Crystal Spectrometer (BCS) and High Energy Transmission Grating (HETG). This paper discusses the principles of operation of BCS and HETG and the results that will be obtained by these instruments. Measurements of individual line strengths obtained by the AXAF spectrometers will allow the application of plasma diagnostic techniques to a study of the detailed physical conditions in celestial objects, particularly in the optically thin plasma of supernova remnants, which is particularly well suited to the application of plasma diagnostics.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Letters and Communications (ISSN 0888-6512); 26; 1-2,
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  • 10
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    The advanced X-ray astrophysics facility - An overview (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: This paper presents an overview of NASA's Advanced X-Ray Astrophysics Facility (AXAF), which is planned for launch in the 1990s and is expected to operate in space for at least 15 years. The design of the X-ray telescope is discussed and the instruments that may fly at the start of the AXAF mission, the principal investigator of each instrument, and the instrument performance parameters are listed. The AXAF instruments will include low-energy and high-energy transimission gratings, a Bragg crystal spectrometer, CCD imagers, an X-ray calorimeter, and a microchannel plate imager. The long lifetime of the AXAF will make it possible to follow up on the HEAO-2/Einstein results, the more recent X-ray observations performed by European and Japanese satellites, and the future ROSAT all-sky survey. The long lifetime of the AXAF, together with the servicing capability that will be offered by the Space Station, will also provide the opportunity of incorporating other instruments into the observatory.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Letters and Communications (ISSN 0888-6512); 26; 1-2,
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  • 11
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    Plasma structures in comets P/Halley and Giacobini-Zinner (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An overview of large-scale plasma phenomena is presented based on results of spacecraft probing of comets Halley and Giacobini-Zinner and on worldwide submissions to the Large-Scale Phenomena Discipline Specialist Team of the International Halley Watch. Examples of tail phenomena and science are presented with emphasis on observed disconnection events. The archive of this material will clearly be very valuable for studying the comet/solar-wind interaction during the 1985-1986 apparition of Halley's comet.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 187; 1-2,
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  • 12
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    IRAS known asteroid prediction and association (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Techniques and procedures employed to obtain data concerning the known asteroids from IRAS observations are discussed. The IRAS observations covered 95 percent of the sky with at least four scans of the telescope field of view. A search was first carried out for geometrical intersections of the trajectories of a given asteroid and the telescope boresight, following which a matched sighting was sought for each such intersection among the actual IRAS point source detections. By using ground based measurements of visual magnitudes, IRAS observations of IR brightness, and a thermal model, albedos and diameters have been computed for 1,822 known asteroids, increasing the amount of this kind of information by about an order of magnitude.
    Schlagwort(e): ASTRONOMY
    Materialart: Journal of the Astronautical Sciences (ISSN 0021-9142); 35; 287-299
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  • 13
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    On the simple models for the interpretation of centimeter-wavelength radio observations of asteroids (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The predictions of the two-layer models used to interpret radio spectra of the asteroids have been examined. It is clear that one must treat the models with caution as the physics is highly simplifed. Although the predictions are in accord with physical expectations, careful attention to the circumstances of the observations is essential. The lack of short-centimeter wavelength measurements of dielectric properties is especially vexing. Some simple improvements to the models based on studies of the lunar radio emission by Keihm and using radar measurements of asteroid surface characteristics by Ostro and colleagues are suggested. Even so, the calculation of a realistic continuum-emission spectrum for asteroidal bodies from 20 cm wavelength to 20 microns wavelength remains a formidable task.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99; 1009-101
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  • 14
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    Observation by Pioneer 7 of He(+) in the distant coma of Halley's comet (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Plasma analyzer data obtained by Pioneer 7 during its approach to about 12.1 million km from the nucleus of Comet P/Halley are presently interpreted as He(+) generated by charge exchange of the solar wind He(2+) with neutral cometary material. The maximum He(+) flux was detected several hours after the closest March 20, 1986 approach of the spacecraft, and is noted to be not only larger than expected, but also to exhibit large, discontinuous flux changes.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 71; 192-197
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  • 15
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    The feasibility of periodicity searches in gamma-ray astronomy (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is presently noted that, in some cases, the usually infeasible conduct of searches in gamma-ray astronomy can be rendered feasible by means of a time-smoothing technique that yields only a moderate sensitivity loss. The total observing time is subdivided into a convenient number m of subintervals, and summing the values of H of each of the subintervals. This will reduce the number of independent frequency values by a factor m due to the shorter observing time.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 175; 1-2,; 353
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  • 16
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    A Palomar Observatory Sky Survey atlas of selected molecular clouds (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Forty-three cold, dense molecular clouds are digitized from the Palomar Observatory Sky Survey glass plates and presented with epoch 1950.0 equatorial coordinates. Regardless of the cloud's extent, the digitized area is limited to a 23 arcmin square on the sky with pixel size of about 1.3 arcsec. The optical maps presented herein are useful for comparing complementary molecular cloud maps from radio or infrared instruments and can be obtained in FITS format for use on astronomical image-processing systems.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 64; 127-129
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  • 17
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    Orbits of the ten small satellites of Uranus (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Orbital elements are presented for the ten small satellites discovered by Voyager 2 at Uranus. These ten new satellites, whose provisional IAU designations are 1985UI and 1986UI through 1986U9, lie for the most part in equatorial, circular orbits; the most notable exception is 1986U8, the outer epsilon-ring shepherd, whose eccentricity e = 0.0101. Unlike the Voyager discoveries at Saturn, which included two co-orbiting satellites and three librators, the ten small Uranian satellites all have quite different semimajor axes.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 93; 1268-127
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  • 18
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    IRAS surface brightness maps of reflection nebulae in the Pleiades (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 313; 853-858
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  • 19
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    The IHW island network (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Early astronomical photography of comets at perihelion encouraged the establishment of an International Halley Watch (IHW) Team for regularly photographing the Comet. The February 1986 period was particularly troublesome due to the limitations of cometary visibility in the Southern Hemisphere. Schmidt cameras were placed on Tahiti, Easter Island, Faraday Station on the Antarctic Peninsula, Reunion Island and in South Africa. Blue- and red-filter B/W images were obtained every night and color prints were occasionally shot. Each night's images were examined before the next night's photography. Several interesting anecdotes are recounted from shipping, manning and operation of the telescopes.
    Schlagwort(e): ASTRONOMY
    Materialart: Sky and Telescope (ISSN 0037-6604); 73; 258-263
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  • 20
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    Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 56; 393-397
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  • 21
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    Techniques for the analysis of data from coded-mask X-ray telescopes (1987)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Several techniques useful in the analysis of data from coded-mask telescopes are presented. Methods of handling changes in the instrument pointing direction are reviewed and ways of using FFT techniques to do the deconvolution considered. Emphasis is on techniques for optimally-coded systems, but it is shown that the range of systems included in this class can be extended through the new concept of 'partial cycle averaging'.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysics and Space Science (ISSN 0004-640X); 136; 2, Au; 337-349
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  • 22
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    X-ray intensity and spectral variations in the BL Lac sources H2155-304 and PKS0548-322 (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The results from the X-ray observations of two BL Lacertae objects, H2155-304 and PKS0548-322, are presented. The observations were carried out with the HEAO-1 A2 Low Energy Detectors, the High Resolution Imager, and the Monitor Proportional Counter aboard the Einstein Observatory. Correlated X-ray intensity variations of about 20 percent in the 0.15-3.5 keV energy band and about 40 percent in the 1.5-10 keV energy band are observed in H2155-304 over a period of about 8 hr. A factor of two change in the intensity of PKS0548-322 in the 3.5-10 keV energy interval is also detected over a time interval of 1 hr. Variations in the X-ray intensity over a timescale of months and the hardening of the spectrum with increasing intensity are seen in the HEAO-1 A2 data on H2155-304. The shortest observed timescale for the variability is used to derive an upper limit on the mass of the central accreting source in the two BL Lac objects studied here.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 227; 525-534
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  • 23
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    The evolution of the infrared emission from the Type II supernova 1980k in NGC 6946 - The dust formation model (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper presents 1-4 micron photometry of supernova 1980 k in NGC 6946 obtained over a period of 1 year following the outburst. During the period between 1980 November 1 and December 19, the infrared emission probably originated from the extended atmosphere of the expanding star. The JHKL colors and a 1.3-2.6-micron spectrum observed during this period correspond to those of a blackbody with an average temperature of about 5000 K. Observations around 1981 May 31 showed that the supernova developed an infrared excess after 1980 December. This infrared excess persisted through 1981 October and is consistent with the appearance of thermal emission from about 700 to 900 K dust in addition to a hotter photosphere. The similarity of this behavior to that of the infrared evolution of some novae suggests that dust formation may be occurring in the supernova ejecta. The hypothesis, that the emission arises from preexisting grains in a circumstellar shell which are heated by the supernova outburst, is also consistent with the data.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 168-174
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  • 24
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    Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. III - Reticon radial velocities (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Radial velocities for 72 stars, most of them known or suspected binaries with F - K giant-supergiant primaries, are derived from Reticon spectra in the region 6005-6235 A at a scale of 7 km/s per diode. Cross-correlation of the spectra normally produces results accurate to better than 1.0 km/s. Eight new radial velocity variables are found (HR 2786, R Pup, HR 3291, HR 4451, HD 114520, HR 5667, HR 7014, and Nu1 Sgr). Improved orbits are determined for 15 known spectroscopic binaries, and provisional orbits are obtained for seven new spectroscopic binaries.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 53; 553-571
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  • 25
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    Infrared observations of RS CVn stars (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper presents infrared photometry of the RS CVn binary stars AR Lac (1.2-10 microns) and MM Her (1.2-3.5 microns) as they egressed from their primary and secondary eclipses; of the eclipsing systems RS CVn and Z Her at maximum light (1.2-10 microns) and of the non-eclipsing systems UX Ari and HR 1099 (1.2-10 microns). An analysis of these and published V data based on flux ratio diagrams (linear analogues of color-color diagrams) shows that G and K stars supply the infrared light of these systems. In AR Lac, the combined light of a G5-K0 subgiant and either a late F dwarf or an early F subgiant can account for the observed visual and infrared light curves. None of these systems shows infrared emission from circumstellar matter. This result is simply understood: dust grains would not be expected to form in the physical conditions surrounding the subgiant, and the corona and chromosphere (whose properties have been deduced from spectroscopic X-ray observations) should not produce appreciable infrared emission.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 205; 859-873
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  • 26
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    Ultraviolet high-resolution spectroscopy from the Space Telescope (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The High Resolution Spectrograph is one of five scientific instruments which will be part of the Space Telescope observatory. The spectrograph was designed to take advantage of the imaging and pointing capabilities of the telescope to obtain ultraviolet spectra with spectral resolution comparable to large, ground-based coudeinstruments. Some of the results of the ground-based testing program will be described, along with applications of these properties to future science programs.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 543-549
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    Theoretical studies of the effects of grain noise on photographic stellar astrometry and photometry (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A method of incorporating the effects of photographic emulsion grain noise into digital image centering algorithms is presented which improves the accuracy of the derived stellar positions and magnitudes. Theoretical formulae are then derived for the limiting error of the center, and the photometric parameters. For IIIa-J, this error is 0.2-0.3 mu for bright unsaturated images, which agrees quite well with measurements made with the Yale PDS microdensitometer. It is expected that, with further improvements in the positional accuracy of the PDS, it should be possible to reach the emulsion grain noise limit, providing that emulsion shifts or other large scale errors do not dominate. It is also shown that, with appropriate trimming, marginal distribution image centering algorithms can yield an accuracy only slightly poorer than that obtained with two-dimensional distributions.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; 1683-168
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  • 28
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    An improved celestial radio reference frame: JPL 1982-4 (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: In the development of a celestial radio reference frame, there are now over 100 sources whose relative positions are known with an average uncertainty less than 5 milliarcseconds. These sources are fairly uniformly distributed over the celestial sphere north of -40 deg declination. Their positions are expressed in the new IAU system. This presentation describes the analysis involved in obtaining these results, as well as future plans for linking this system to the JPL planetary ephemerides.
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  • 29
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    Comet Halley ephemeris uncertainties in 1985-1986 (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): ASTRONOMY
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    Dust particles in the anomalous tail of Comet Kohoutek (1973 XII) (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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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    Cometary nucleus and active regions (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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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  • 32
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    Regions of stability of asteroids (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
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  • 33
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    The JPL 'long ephemeris', DE102/LE51 (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): ASTRONOMY
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  • 34
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    Dynamical evolution of the Oort cometary cloud (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
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  • 35
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    Properties of young clusters near reflection nebulae (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Near infrared observations in the reflection nebulae NGC 703, 2023, and 2068 are used to study clusters of young stars found associated with these nebulae. At least 30 percent to 60 percent of these stars are pre-main sequence objects, as indicated by their infrared excesses, hydrogen line emission, or irregular variability. The spatial distributions and observed luminosity functions of these young open clusters are derived, and the inferred mass function and star formation efficiencies are discussed. Previously announced in STAR as N83-25628
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; July 198
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  • 36
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    Cometary impacts with the sun - Physical and dynamical considerations (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Michels et al. (1982) observed the apparent impacting of the sun by a comet, and Sekanina (1982) showed that the comet, 1979XI, was probably a member of the Kreutz group of sun-grazing comets, although its perihelion of 0.35 solar radii was much smaller than the 1.2-1.9 solar radii common for this comet class. The perihelion change cannot be explained by planetary, stellar, or nongravitational perturbations. The most plausible explanation is collision with another body, probably a comet, at large heliocentric distance. The probability of such an event is, however, extremely small. The sublimation of the comet's nucleus before impact is discussed, and it is suggested that its ultimate destruction probably resulted from the shock of entry into the denser regions of the solar atmosphere, just above the photosphere.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 55; Sept
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  • 37
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    An infrared study of the eclipsing dwarf nova U Geminorum (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: One series of data comprising the present J, H, K broadband IR photometry of the cataclysmic binary system U Geminorum over the course of two orbital cycles was obtained several days before an outburst, while a second was gathered when the system had almost completely returned to quiescence from that outburst. In quiescence, the M4-M5.5 red dwarf star supplies most of the IR luminosity of the system, while the light curves at this time are tidally induced ellipsoidal variations of the red dwarf which exhibit an amplitude such that the red dwarf must fill, or nearly fill, its Roche lobe. This shows directly that Roche lobe overflow is important in cataclysmic variable stars. The range of the disk IR colors after outbursts suggest that cool and optically thick gas, together with optically thin gas, supply most of the IR light of the disk.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 204; Sept
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  • 38
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    Very large spiral galaxies (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: As a first step in the systematic study of large spirals, which may be useful in cosmological tests and studies of galaxy evolution, a catalog of the 107 largest known spiral galaxies is presented. Catalog galaxies have isophotal diameters greater than 90 kpc, assuming an H(zero) value of 50 km/sec per Mpc. UBVR photoelectric photometry is presented for 20 of these galaxies, and absolute magnitudes are derived for all galaxies in the catalog by transforming Zwicky magnitudes to the B(T) system.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 204; Sept
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  • 39
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    Further studies on criteria for the onset of dynamical instability in general three-body systems (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Numerical experiments designed for the elucidation of the conditions under which self-gravitating, three-body systems become dynamically unstable are examined of the cases of four orbital configuration types: circular, prograde, and coplanar; circular, retrograde, and coplanar; circular, direct, and inclined; and eccentric, direct, and coplanar. Results indicate that orbital inclination does not significantly affect stability in 'outer planet' configurations, while the stability of 'inner planet' configurations, where the tertiary is in close orbit about one member of the binary, is markedly less affected, once the relative orbital inclination is greater than 50 deg. It is found that the onset of dynamical instability is only weakly dependent on the eccentricity of either the binary or tertiary orbit, as long as the mass of the tertiary is comparable to the reduced mass of the binary.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; Sept
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  • 40
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    DE 102 - A numerically integrated ephemeris of the moon and planets spanning forty-four centuries (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is pointed out that the 1960's were the turning point for the generation of lunar and planetary ephemerides. All previous measurements of the positions of solar system bodies were optical angular measurements. New technological improvements leading to immense changes in observational accuracy are related to developments concerning radar, Viking landers on Mars, and laser ranges to lunar corner cube retroreflectors. Suitable numerical integration techniques and more comprehensive physical models were developed to match the accuracy of the modern data types. The present investigation is concerned with the first integrated ephemeris, DE 102, which covers the entire span of the historical astronomical observations of usable accuracy which are known. The fit is made to modern data. The integration spans the time period from 1411 BC to 3002 AD.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 125; 1, Au; Aug. 198
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  • 41
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    The IRAS telescope (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The IRAS telescope is described in terms of its system configuration and physical characteristics, subsystem functions and descriptions, and performance characteristics. The mission and the configuration are reviewed briefly, and the major functional components of the telescope are described, including the focal plane assembly, the optics, the electronics, the cryogenics, and the thermal control. Exploded and cross-sectional views and block diagrams are presented for the telescope system configuration, focal plane assembly, infrared subarray module, optical subsystem, infrared channel data flow, and main cryogen dewar. The telescope physical characteristics are listed. The performance characteristics are listed and discussed, including the spectral response, sensitivity, optical quality, and photometric accuracy. Relative system spectral response curves for the infrared bands are shown.
    Schlagwort(e): ASTRONOMY
    Materialart: vol. 36; Jan. 198
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  • 42
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    Coordinate systems (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Jovian coordinate systems are different from those employed in the case of the earth. Latitude and longitude coordinates are usually established relative to some solid surface. Because Jupiter does not have a solid surface (at least none which is visible through the clouds), arbitrary, but convenient, coordinate grids have been prescribed. A spin equator is made out from observations of cloud motion, and the direction of the planetary spin axis is, therefore, determined with relatively good accuracy. The problem in establishing a Jupiter longitude system is that the mean rotation period of the clouds is a function of latitude. The solution selected was to define two separate longitude grids. A third longitude system became necessary with the detection of radio signals which gave evidence for a rotating planetary magnetic field. Attention is also given to orbital phase angle and longitude conventions for satellites, and two latitude systems for Jupiter
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    Transformations of the perturbed two-body problem to unperturbed harmonic oscillators (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Singular, nonlinear, and Liapunov unstable equations are made regular and linear through transformations that change the perturbed planar problem of two bodies into unperturbed and undamped harmonic oscillators with constant coefficients, so that the stable solution may be immediately written in terms of the new variables. The use of arbitrary and special functions for the transformations allows the systematic discussion of previously introduced and novel anomalies. For the case of the unperturbed two-body problem, it is proved that if transformations are power functions of the radial variable, only the eccentric and the true anomalies (with the corresponding transformations of the radial variable) will result in harmonic oscillators. The present method significantly reduces computation requirements in autonomous space operations.
    Schlagwort(e): ASTRONOMY
    Materialart: Celestial Mechanics (ISSN 0008-8714); 30; May 1983
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  • 44
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    Revised orbits for 105 Herculis and Pi Cephei A and a model for the Pi Cephei system (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: New orbital elements for the giant primary components of 105 Herculis and Pi Cephei A are derived using radial velocities from Dominion Astrophysical Observatory coude plates. These data are combined with those of Harper (1925) in order to estimate the velocity amplitude of Pi Cephei A in the visual orbit of this triple system. Two models of this system are developed. In the first model, the unseen spectroscopic secondary component is a single main-sequence star, although this seems unlikely, while in the alternative model the unseen secondary component is itself double.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society; vol. 203
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    Maintaining an expert system for the Hubble Space Telescope ground support (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The transformation portion of the Hubble Space Telescope (HST) Proposal Entry Processor System converts astronomer-oriented description of a scientific observing program into a detailed description of the parameters needed for planning and scheduling. The transformation system is one of a very few rulebased expert systems that has ever entered an operational phase. The day to day operations of the system and its rulebase are no longer the responsibility of the original developer. As a result, software engineering properties of the rulebased approach become more important. Maintenance issues associated with the coupling of rules within a rulebased system are discussed and a method is offered for partitioning a rulebase so that the amount of knowledge needed to modify the rulebase is minimized. This method is also used to develop a measure of the coupling strength of the rulebase.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Goddard Space Flight Center, Proceedings of 1987 Goddard Conference on Space Applications of Artificial Intelligence (AI) and Robotics; p 1-1
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    Optical electronics for meteor observations (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Spectral observations of meteors have been carried out for several years using an optical electronics facility. Interest has centered on faint meteors and their trails in the period of intensive meteor showers. Over 800 meteors were registered during the observation period, with spectrograms obtained for 170 of these. A total of 86 meteors were photographed from two sites and for 25 of these spectrograms of the meteors as well as their trails were obtained. All meteors have undergone routine processing in order to determine atmospheric characteristics. Results are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 25; p 410-415
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    Imaging interferometry with non-redundant arrays (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The performance of a set of nonredundant arrays, that convert an existing telescope to an interferometer, was simulated. Each array is a perforated mask, placed at an image of the objective. Each pair of holes in a mask transmits a unique spatial frequency that is present in the target; hence the term nonredundant. Each mask produces a fringe I(f) in the focal plane that is the product of the Fourier transforms of the object and the optical transfer function S(f).
    Schlagwort(e): ASTRONOMY
    Materialart: NASA-Goddard Space Flight Center, Theoretical Problems in High Resolution Solar Physics, 2; p 143-144
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    Spectroscopy and nonthermal processes (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Stellar spectra are analyzed to determine nonthermal processes for cool stars. A shock wave crossing model is supported by a study of the behavior of absorption and emission spectra. The shock waves are attributed to atmospheric kinetics. Circumstellar spectral lines are studied for information about gaseous circumstellar layers. The description of stellar envelopes is carried on through circumstellar dust. Characteristic properties of polarization in the dust are described in the case of specific stars, emphasizing narrowband observations in Mira, semiregular, and supergiant stars. Finally, the direct approach to measuring the angular diameters of stars and mapping the distribution of circumstellar dust and gas by lunar occultation or interferometry is discussed, using two prototype stars, an M supergiant and a dusty carbon star.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington, The M-Type Stars; p 113-207
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  • 49
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    Lunar luminescence measurements (1983)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: Spectra of lunar sites obtained in June 1983 have been analyzed for residual luminescence using the spectral line depth technique. The results or three sites each at three wavelengths are presented. The sites observed were Mare Crisium, Kepler, and Aristarchus. In each case, the value quoted was based not only on the strong Fraunhofer line in the spectral range covered but also on from 11 to 21 weaker lines within 80 A of the strongest feature. These data do not support previous observations. The values given do not indicate a greatly reddened spectrum, and the luminescence spectrum of the mare site is not significantly different from the two young crater sites. These observations cannot be adequately explained by thermal luminescence, theories of direct excitation are also unable to explain the strength of the flux.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
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    Radio Astronomy (1983)
    In:  CASI
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    Publikationsdatum: 2014-09-12
    Beschreibung: Deep Space Network (DSN) 26- and 64-meter antenna stations were utilized in support of Radio Astronomy Experiment Selection Panel experiments. Within a time span of 10 days, in May 1983 (267.75 hours total), nine RAES experiments were supported. Most of these experiments involved multifacility interferometry using Mark 3 data recording terminals and as many as six non-DSN observatories. Investigations of black holes, quasars, galaxies, and radio sources are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: The Telecommun. and Data Acquisition Rept.; p 112-113
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    Upper Limits to the Annihilation Radiation Luminosity of Centaurus a (1983)
    In:  CASI
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    Publikationsdatum: 2014-09-10
    Beschreibung: A high resolution observation of the active nucleus galaxy Centaurus A (NGC 5128) was made by the GSFC low energy gamma-ray spectrometer (LEGS) during a balloon flight on 1981 November 19. The measured spectrum between 70 and 500 keV is well represented by a power law of the form 1.05 x 10 (-4) (E/100 keV) (-1.59) ph/sq cm /s with no breaks or line features observed. The 98% confidence (2 sigma) flux upper limit for a narrow ( 3 keV) 511-keV positron annihilation line is 9.9 x 10 (-4) ph/ sq cm /s. Using this upper limit, the ratio of the narrow-line annihilation radiation luminosity to the integral or = 511 keV luminosity is estimated to be 0.09 (2 sigma upper limit). This is compared with the measured value for our galactic center in the Fall of 1979 of 0.10 to 0.13, indicating a difference in he emission regions in the nuclei of the two galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 39-44
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    Ultraviolet spectral morphology of the O stars. IV - The OB supergiant sequence (1987)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An atlas of 25 O3-B8 supergiant spectra in the wavelength ranges 1320-1580 A and 1620-1880 A is presented, based on high-resolution data from the IUE archives. The remarkably detailed relationship between the stellar-wind profiles and the optical spectral classifications throughout this sequence is emphasized. For instance, the (Si IV)/(C IV) ratio reverses between O4 and O6.5; and the B0, B0.5, and B0.7 Ia wind characteristics are each qualitatively unique and distinct from one another. The systematic behavior of nine stellar-wind features with ionization potentials ranging from 114 to 19 eV is summarized as a function of advancing spectral type.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 99; 40-53
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    HD 207739 - A strange composite star (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: This star, classified F8 IIe + B:, has a very unusual ultraviolet spectrum, with abnormally strong and numerous absorption features in the far-UV and exceptionally strong Mg II emission. There is some resemblance to shell and pre-main-sequence B stars, but it more closely matches the strange spectra of the eclipsing systems VV Cep and SX Cas, and it probably has considerable circumstellar material at fairly high temperature. HD 207739 is probably an interacting binary and needs to be monitored for light and velocity variations.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal; vol. 264
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    Infrared-ultraviolet spectra of active galactic nuclei (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Data from IRAS and IUE were combined with ground based optical and infrared spectrophotometry to derive emission line free spectral energy distributions (SEDs) for 29 active galactic nuclei (AGNs) between 0.1 and 100 microns. The IRAS data were scaled down to account for extended emission. These correction factors, determined by comparing small aperture ground based 10.6 micron data with large aperture IRAS 12 micron fluxes, were usually less than 25%. These corrected SEDs are shown.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 727-729
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    Spectrophotometery of Brackett lines in very luminous IRAS galaxies (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Observation of the Brackett-alpha and Brackett-gamma hydrogen recombination lines were made in a sample of galaxies chosen from the IRAS catalog to have high luminosities at infrared wavelengths. Most have strong Brackett line emission indicating large numbers of high mass stars; the formation of these stars may hence be the underlying source for the galaxies' luminosities. However, there are at least two exceptions that may not be explained in this manner: NGC 6240 and Arp 220. Additional evidence indicates that each of these exceptions may be more closely related to Seyfert-type galaxies or other active galactic nuclei.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 701-705
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  • 56
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    A very deep IRAS survey at l(II) = 97 deg, b(II) = +30 deg (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A deep far-infrared survey is presented using over 1000 scans made of a 4 to 6 sq. deg. field at the north ecliptic pole by the IRAS. Point sources from this survey are up to 100 times fainter than the IRAS point source catalog at 12 and 25 micrometers, and up to 10 times fainter at 60 and 100 micrometers. The 12 and 25 micrometer maps are instrumental noise-limited, and the 60 and 100 micrometer maps are confusion noise-limited. The majority of the 12 micrometer point sources are stars within the Milky Way. The 25 micrometer sources are composed almost equally of stars and galaxies. About 80% of the 60 micrometer sources correspond to galaxies on Palomar Observatory Sky Survey (POSS) enlargements. The remaining 20% are probably galaxies below the POSS detection limit. The differential source counts are presented and compared with what is predicted by the Bahcall and Soneira Standard Galaxy Model using the B-V-12 micrometer colors of stars without circumstellar dust shells given by Waters, Cote and Aumann. The 60 micrometer source counts are inconsistent with those predicted for a uniformly distributed, nonevolving universe. The implications are briefly discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 547-552
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  • 57
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    The initial mass function in HII galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Observation of a large sample of HII galaxies shows that the emission line ratios of the youngest objects change systematically with gaseous oxygen abundance, which was interpreted as resulting from changes in the initial mass function (IMF) of the ionizing cluster. Comparison with cluster/nebula models shows that both the slope and the upper mass limit of the cluster IMF vary with abundance. In HII galaxies with oxygen abundance about 1/10 that of Orion, the IMF for massive stars must have a slope which is about a factor of 2 smaller than in the Solar Neighborhood.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 479-482
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  • 58
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    Extragalactic infrared spectroscopy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The spectra of galaxies in the near infrared atmospheric transmission windows are explored. Emission lines were detected due to molecular hydrogen, atomic hydrogen recombination lines, a line attributed to FEII, and a broad CO absorption feature. Lines due to H2 and FEII are especially strong in interacting and merging galaxies, but they were also detected in Seyferts and normal spirals. These lines appear to be shock excited. Multi-aperture measurements show that they emanate from regions as large as 15 kpc. It is argued that starbursts provide the most plausible and consistent model for the excitation of these lines, but the changes of relative line intensity of various species with aperture suggest that other excitation mechanisms are also operating in the outer regions of these galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 421-433
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  • 59
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    CO observations of galaxies with the Nobeyama 45-M telescope (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: High-resolution (15 inch), filled aperture maps of the CO (J = 1-0) line emission were obtained for several nearby, CO-bright galaxies like M82, M83, IC342, and NGC891 in order to study star forming activity in these galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 179-196
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  • 60
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    A correlation between the IRAS infrared cirrus at 60 or 100 microns and neutral atomic hydrogen in the outer galaxy (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: A linear correlation was found between the infrared cirrus at 100 or 60 microns and neutral atomic hydrogen near the galactic plane. Infrared Astronomy Satellite (IRAS) Sky Brightness images were compared to the 0.5 deg resolution Weaver-Williams HI survey in two regions of the outer Galaxy near l = 125 deg and l = 215 deg. The dust temperature inferred is nearly uniform and in reasonable agreement with theoretical predictions of thermal dust emission.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 103-105
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    The Arp Ring: Galactic or extragalactic? (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The Arp Ring is a faint, loop-like structure around the northern end of M81 which becomes apparent only on deep optical photographs of the galaxy. The nature of the Ring and its proximity to M81 are uncertain. Is it simply foreground structure, part of this galaxy, or is it within the M81 system? Infrared Astronomy Satellite (IRAS) maps of the region show a far-infrared counterpart of the Ring. The infrared data are compared with previous optical and radio observations to try to ascertain its physical nature. The poor correlation found between the common infrared/optical structure and the distribution of extragalactic neutral hydrogen, and the fact that its infrared properties are indistinguishable from those of nearby galactic cirrus, imply that the Arp Ring is simply a ring structure in the galactic cirrus.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 107-110
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  • 62
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    Erratum: IRAS observations of irregular galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: In Infrared Astronomy Satellite (IRAS) observations of irregular galaxies, galactic blue luminosities were based on standard optical definitions. The blue luminosities (L sub B) were derived from the blue absolute magnitude (M sub B) or form the in band flux. However, the L sub B system for spiral galaxies was based on quasi-bolometric (rather than in band) fluxes. The formulation and resulting statements are corrected.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 257
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  • 63
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    IRAS observations of irregular galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Normal irregular galaxies seem to be unusual in having vigorous star formation yet lacking the many dark nebulae typical of spirals. The Infrared Astronomy Satellite (IRAS) observations of a large sample of irregulars are used to explore the dust contents of these galaxies. Compared to normal spirals, the irregulars generally have higher L sub IR/L sub B ratios, warmer f(100)/f(60) dust color temperatures, and lower globally-averaged dust/gas ratios. The relationship between the infrared data and various global optical properties of the galaxies is discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 253-256
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  • 64
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    Stellar bars and the spatial distribution of infrared luminosity (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Ground-based 10 micron observations of the central region of over 100 infrared luminous galaxies are presented. A first order estimate of the spatial distribution of infrared emission in galaxies is obtained through a combination of ground-based and Infrared Astronomy Satellite (IRAS) data. The galaxies are nearby and primarily noninteracting, permitting an unbiased investigation of correlations with Hubble type. Approximately 40% of the early-type barred galaxies in this sample are associated with enhanced luminosity in the central (approximately 1 kpc diameter) region. The underlying luminosity source is attributed to both Seyfert and star formation activity. Late-type spirals are different in that the spatial distribution of infrared emission and the infrared luminoisty are not strongly dependent on barred morphology.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 219-226
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  • 65
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    IRAS observations of the Pleiades (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The Infrared Astronomy Satellite (IRAS) observations of the Pleiades region are reported. The data show large flux densities at 12 and 25 microns, extended over the optical nebulosity. This strong excess emission, implying temperatures of a few hundred degrees Kelvin, indicates a population of very small grains in the Pleiades. It is suggested that these grains are similar to the small grains needed to explain the surface brightness measurements made in the ultraviolet.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 117-121
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  • 66
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    Infrared properties of dust grains derived from IRAS observations (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The analysis of several diffuse interstellar clouds observed by the Infrared Astronomy Satellite (IRAS) is presented. The 60/100 micron flux ratios appear to be nearly constant in clouds with up to 1 sup m visual extinction at the center. Observations of a highly regular cloud in Chamaeleon show that the 12/100 micron ratio peaks at an intermediate radial distance and declines towards the center of the cloud. These observations indicate that nonequilibrium emission accounts only for the 12 and 25 micron bands; strong emission observed at the 60 micron band is probably due to equilibrium thermal radiation. The correlation of the 12 micron emission with a red excess observed for a high latitude cloud, L1780, is shown to be consistent with the assumption that both features are due to fluorescence by the same molecular species.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 113-116
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  • 67
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    On the redistribution of OB star luminosity and the warming of nearby molecular clouds (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Infrared Astronomy Satellite (IRAS) observations of the neighborhoods of six outer-Galaxy HII regions were combined with CO observations to show that most of the far infrared (FIR) luminosity from within approximately 25 to 75 pc of the ionizing stars is contributed by dust in molecular clouds, not by dust in the low-density ionized gas. Dust associated with the clouds is warmed by absorption of UV and visible light from the cluster of stars responsible for the ionization. Most of the OB cluster starlight is not absorbed locally. A fraction of the order of 10% of the OB cluster luminosity is absorbed by nearby molecular clouds and reradiated as FIR light. The luminosity per unit mass for the heated clouds is approximately 3 to 13 solar luminosity/solar mass, approximately one order of magnitude greater than the corresponding ratio for clouds found near clusters without O stars, and two orders of magnitude greater than the ratio for dark clouds heated primarily by the interstellar radiation field. If the observations of clouds near outer-Galaxy HII regions are used to characterize the molecular clouds heated by HII regions in the inner-Galaxy, then at most 30% of the Galaxy's molecular cloud mass is actively engaged in the formation of massive stars at the present time.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 75-78
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    High energy gamma ray astronomy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.
    Schlagwort(e): ASTRONOMY
    Materialart: Essays in Space Science; p 227-274
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  • 69
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    Space Infrared Telescope Facility (SIRTF) design and thermal analysis (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The design and performance characteristics of an observatory are compared with those of a storage dewar. The critical design technologies required to increase cryogen dewar lifetime are discussed. In particular, outer shell temperature, vapor cooled shields, multilayer insulation performance, and tank support systems are analyzed to assess their impact on cryogen lifetime for both the observatory and the storage dewar. The cryogen lifetime and cryogen mass loss rate of the Space Infrared Telescope Facility (SIRTF) are compared with that of the Infrared Astronomy Satellite and the Cosmic Background Explorer Satellite. A 0.1 percent mass loss per day of superfluid helium dewar can be designed using current state-of-the-art dewar technology. Space-based liquid hydrogen and liquid oxygen tanks can be designed for a 5-year lifetime.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Lewis Research Center, Cleveland, Ohio. Cryogenic Fluid Management Technology Workshop. Volume 1: Presentation Material and Discussion; p 193-220
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  • 70
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    The radio-far infrared correlation: Spiral and blue compact dwarf galaxies opposed (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The recently established correlation between radio continuum and far infrared emission in galaxies was further investigated by comparing normal spiral and blue compact dwarf galaxies. The puzzling result is that the ratio of radio to far infrared luminosity and its dispersion is the same for both samples, although their ratios of blue to far infrared luminosity, their radio spectral indices and their dust temperatures exhibit markedly different mean values and dispersions. This suggests that the amount of energy radiated in the two regimes is enhanced in the same way although the mechanisms responsible for the two components are rather different and complex. The fact that the blue light does not increase at the same proportion shows that both the radio and the far infrared emission are connected with the recent star formation history.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 583-588
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  • 71
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    Radio and infrared observations of (almost) one hundred non-Seyfert Markarian galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The 13 cm flux densities of 96 non-Seyfert Markarian galaxies were measured at Arecibo Observatory. Far infrared flux densities have been published for 78 of these galaxies in the IRAS catalog. The radio, infrared, and optical fluxes of these galaxies and of a magnitude limited sample of normal galaxies were compared to clarify the nature of the radio emission in Markarian galaxies. It was found that Markarian galaxies of a given apparent magnitude and Hubble type generally have radio fluxes several times higher that the fluxes typical of normal galaxies of the same magnitude and type. Remarkably, the ratio of radio flux to far infrared flux is nearly the same for most of these starburst galaxies and for normal spiral disks. However, the compact and peculiar Markarian galaxies consistently have about 60% more radio flux per unit infrared flux than the other Markarian galaxies and the normal spirals. It is not clear whether this difference reflects a difference in the evolution of the starbursts in these galaxies or whether there is excess radio emission of nonstellar origin.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 579-582
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    The infrared morphology of galactic centers (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Initial results are presented of a program to map the centers of galaxies in the mid-infrared using the NASA-MSFC 20 pixel bolometer array. Maps at 10.8 micrometer of the galaxies NGC 5236 (M82), NGC 1808, NGC 4536, and NGC 4527 reveal complex emitting regions ranging in size from 500 pc to 2 kpc. The infrared spatial distributions generally resemble those in the visible and radio. In all cases a large fraction of the IRAS 12 micrometer flux originates in spatial structures prominent in the maps.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 497-500
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  • 73
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    The azimuthal and radial distributions of HI and H2 in NGC 6946 (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A study was completed of the atomic and molecular components of the ISM in NGC 6946. The distribution of molecular clouds was determined from a fully sampled CO map of the inner disk using the 14-meter telescope of the FCRAO. The distribution of atomic gas was derived from VLA observations at 40" resolution in the D configuration. When comparing the global CO and HI properties with other components of the galaxy, it was found that the azimuthally averaged radial distributions of CO, H-alpha, radio continuum and blue light all exhibit similar roughly exponential falloffs, while the azimuthally averaged HI surface densities vary by only a factor of 2 out to R = 16 kpc. This indicates that while the H-alpha/CO ratio is approximately constant with radius, the CO/HI ratio decreases by a factor of 30 from the center of the galaxy to R = 10 kpc.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 491-495
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  • 74
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    VLA continuum observations of barred spiral galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Observations of NGC 613, NGC 1300, NGC 4314 and NGC 5383 using the VLA at frequencies of 1464.9 and 4885.1 MHz are reported. These objects are a subset of galaxies from which radio emission were searched. The selection criteria were: (1) they are barred spiral galaxies preferentially with different Hubble type; (2) they have a peculiar or hot spot nucleus; (3) they have been observed at far infrared wavelengths by IRAS; and (4) they are observable from the northern hemisphere. Their radio and far infrared properties are summarized and their composite spectra are shown.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 483-484
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    IRAS observations of starburst galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Far infrared properties of Starburst galaxies were analyzed using IRAS observations at 25, 60, and 100 micrometers. Seventy-nine of 102 Starburst galaxies from the list of Balzano were detected. These galaxies have high IR luminosities of up to a few 10 to the 12th power L sub 0 and concentrate in a small area of the IR color - color diagram. The IR power law spectral indices, alpha, lie within the ranges -2.5 〈alpha(60,25)〈 -1.5 and -1.5 〈alpha(100,60)〈 0. These observed indices can be interpreted in terms of a cold disk component and a warm component. More than 80% of the 60 micrometer emission comes from the warm component. The fraction of the 60 micrometer emission attributable to the warm component can be used as an activity indicator.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 507-511
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    Ultraluminous infrared galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The IRAS survey of the local universe has revealed the existence of a class of ultraluminous infrared galaxies with L(8 to 1000 micrometer) greater than 10 to the 12th L sub 0 that are slightly more numerous, and as luminous as optically selected quasars at similar redshift. Optical CCD images of these infrared galaxies show that nearly all are advanced mergers. Millimeter wave CO observations indicate that these interacting systems are extremely rich in molecular gas with total H2 masses 1 to 3 x 10 to the 10th power M sub 0. Nearly all of the ultraluminous infrared galaxies show some evidence in their optical spectra for nonthermal nuclear activity. It is proposed that their infrared luminosity is powered by an embedded active nucleus and a nuclear starburst both of which are fueled by the tremendous reservoir of molecular gas. Once these merger nuclei shed their obscuring dust, allowing the AGN to visually dominate the decaying starburst, they become the optically selected quasars.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 411-420
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  • 77
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    Modelling the IRAS colors of galaxies (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A physical interpretation is proposed for the color-color diagram of galaxies which are powered only by star formation. The colors of each galaxy result from the combination of two components: cirrus-like emission from the neutral disk, and warmer emission from regions directly involved in on-going star formation. This approach to modelling the emission is based on dust properties, but independent evidence for it is found in the relation between the color sequence and the luminosity sequence. Implications of data and interpretations are discussed and possible tests mentioned for the model.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 319-322
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  • 78
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    IRAS colors of VLA identified objects in the galaxy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Infrared Astronomy Satellite (IRAS) sources found within 4 degrees of l = 125 deg, b = 2 deg on the 3rd HCON 60 micron Sky Brightness Images were observed at the Very Large Array (VLA). Regions were to be identified where massive stars are forming by looking for small areas of radio continuum emissions. The IRAS sources could be divided into three groups by their IRAS 12 micron/25 micron and 60 micron/100 micron color. The group identified with star forming regions contained essentially all of the objects with extended radio emission. In all of these cases the extended radio emission showed a morphology consistent with the identification of these objects as HII regions. The conclusion drawn is that star formation regions can be distinguished from other objects by their infrared colors.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA, Washington Star Formation in Galaxies; p 63-66
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  • 79
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    Infrared astronomy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The role and contributions of Frank McDonald in extending high energy astrophysics to the sub-eV photon energy range (in putting infrared astronomy into orbit) are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: Essays in Space Science; p 395-401
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    X-ray astronomical spectroscopy (1987)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: The contributions of the Goddard group to the history of X-ray astronomy are numerous and varied. One role that the group has continued to play involves the pursuit of techniques for the measurement and interpretation of the X-ray spectra of cosmic sources. The latest development is the selection of the X-ray microcalorimeter for the Advanced X-ray Astrophysics Facility (AXAF) study payload. This technology is likely to revolutionize the study of cosmic X-ray spectra.
    Schlagwort(e): ASTRONOMY
    Materialart: Essays in Space Science; p 379-394
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    Hubble Space Telescope (1987)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The Hubble Space Telescope will employ magnetic torque controllers, which make use of the Earth's magnetic field augmented by four reaction wheels. DC torques are easily allowed for, but variations, orbit by orbit, can result in excessive wheel speeds which can excite vibratory modes in the telescope structure. If the angular momentum from aerodynamic sources exceeds its allocation of 100 Nms, the excess has to come out of the maneuvering budget since the total capacity of the momentum storage system is fixed at 500 Nms. This would mean that maneuvers could not be made as quickly, and this would reduce the amount of science return. In summary, there is a definite need for a model that accurately portrays short term (within orbit) variations in density for use in angular momentum management analyses. It would be desirable to have a simplified model that could be used for planning purposes; perhaps applicable only over a limited altitude range (400 to 700 km) and limited latitude band.
    Schlagwort(e): ASTRONOMY
    Materialart: Upper and Middle Atmospheric Density Modeling Requirements for Spacecraft Design and Operations; p 73-87
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  • 82
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    U.S. data processing for the IRAS project (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The JPL's Scientific Data Analysis System (SDAS), which will process IRAS data and produce a catalogue of perhaps a million infrared sources in the sky, as well as other information for astronomical records, is described. The purposes of SDAS are discussed, and the major SDAS processors are shown in block diagram. The catalogue processing is addressed, mentioning the basic processing steps which will be applied to raw detector data. Signal reconstruction and conversion to astrophysical units, source detection, source confirmation, data management, and survey data products are considered in detail.
    Schlagwort(e): ASTRONOMY
    Materialart: vol. 36; Jan. 198
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  • 83
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    Experimental test of the variability of G using Viking lander ranging data (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Results are presented from the analysis of solar-system astrometric data, notably the range data to the Viking landers on Mars. A least-squares fit of the parameters of the solar system model to these data limits a simple time variation in the effective Newtonian gravitational constant to (2 + or - 4) x 10 to the -12th/yr and a rate of drift of atomic clocks relative to the implicit clock of relativistic dynamics to (1 + or - 8) x 10 to the -12th/yr. The error limits quoted are the result of uncertainties in the masses of the asteroids.
    Schlagwort(e): ASTRONOMY
    Materialart: Physical Review Letters (ISSN 0031-9007); 51; 1609-161
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  • 84
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    Astrometry (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Progress in astrometry is reviewed. Aspects of photographic astrometry are addressed, including the use and optimization of emulsions as detectors and the application of side-field and long-focus photographic astrometry to the determination of stellar positions, to proper motion surveys, the determination of more accurate parallaxes, the study of binaries, and the examination of the membership and internal motions of star clusters. The advantages and disadvantages of photoelectric astrometry are summarized, and the instruments used in this field is discussed, including scanners, detector arrays, stellar interferometers, space telescopes, and satellites. Promising observational methods for studying binary stars are addressed. Astrometry derived from meridian circle observations is considered, emphasizing the FK4 system. The use of radio astrometry is briefly discussed.
    Schlagwort(e): ASTRONOMY
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  • 85
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    Photoelectric photometry of selected SAO stars. III (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Photometric observations of 131 SAO stars for use in calibrating data obtained from the Near Infrared Photographic Sky Survey (NIPSS) are reported. The serial numbers of the primary NIPSS program fields in which the photometry was done are shown along with the approximate position of each field and the number of stars observed in each field. The observations are listed, showing the SAO numbers of the program stars, their 1950 equatorial coordinates, the V magnitudes, and the (V-R) and (V-I) color indices. The mean errors in magnitudes and color indices obtained by averaging deviations from the mean for each star are on the order of 0.02 mag.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 876
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  • 86
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    The unique cometary nebula Parsamian 13 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Parsamian 13 is found to be a cometary nebula, with a deeply embedded star suffering strong absorption by silicate grains. A feature near 2.7 microns, attributed to absorption by terminal OH groups, may represent the first detection in an astrophysical environment of water ice grains diluted by another molecule, for example by CO. The bolometric luminosity suggests that this star is either an extremely young T Tauri star or an evolved low-mass star, now a red giant, high on its convective track. Most unusual is the presence of cold (50 K) TiO gas in sufficient abundance to show in absorption in the optical and very near-infrared regions; this material probably represents very recently expelled photospheric layers.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 273; 624-632
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  • 87
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    The future of VLBI observatories in space (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The angular resolution of radio maps made by earth-based VLBI observations can be exceeded by placing at least one element of a VLBI array into earth orbit. A VLBI observatory in space can offer the additional advantages of increased sky coverage, higher density sampling of Fourier components, and rapid mapping of objects whose structure changes in less than a day. This paper explores the future of this technique.
    Schlagwort(e): ASTRONOMY
    Format: text
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  • 88
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    Radio stars - A possible link between the Hipparcos optical reference frame and an extra-galactic very long baseline interferometry reference frame (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The concept of typing the Hipparcos optical and the JPL VLBI frames of reference by means of VLBI measurements of the positions and proper motions of the radio components of some bright stars is considered. The properties of the thermal and non-thermal radio-stars are discussed and 22 candidate stars are selected to achieve this tie. A description is given of the first VLBI attempt to detect these stars on the intercontinental baselines of the Deep Space Network with the Mark II recording system.
    Schlagwort(e): ASTRONOMY
    Format: text
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  • 89
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    Earth rotation from lunar laser ranging (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The rotational orientation (Universal Time and the variation of latitude at McDonald Observatory, Texas) of the earth has been determined between mid 1970 and mid 1982 from McDonald Observatory lunar laser ranging (LLR) data. Universal Time, UT1, is calculated and supplied in three forms, the raw daily decomposition values, the Gaussian filtered values and the Fourier smoothed values. Formal error estimates are available for all three types. LLR can calculate corrections to one component of polar motion, the variation of latitude at McDonald Observatory. Modelling improvements have been applied here and a significant drop is seen in the residuals. The rms weighted residual for the entire thirteen year data span (3,326 'normal' points acquired between August 1969 and May 1982) is 18.7 cm.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 54; 519-540
    Format: text
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  • 90
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    A large aperture balloon-borne telescope for a submillimeter wavelength survey of the galactic plane (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: A balloon-borne, 1.2 meter Cassegrain telescope with a servo-controlled chopping secondary mirror has been developed and used to survey the Galactic Plane at submillimeter wavelengths. The telescope pointing system uses a gyroscope as the primary stabilization reference and makes use of microprocessors for pointing control, on-board data collection, and telemetry formatting. A description of the telescope, multi-channel liquid-helium-cooled focal plane and the aspect and orientation subsystems are presented.
    Schlagwort(e): ASTRONOMY
    Materialart: (ISSN 0273-1177)
    Format: text
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  • 91
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    Experimental limits of the extreme ultraviolet background (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Photometric observations of the diffuse extreme ultraviolet background with two photometers having bandpasses of 750-940 A and 1040-1080 A are reported. The payload, which was flown aboard an ARIES sounding rocket in June 1982, is described, including the electron detectors, filters, and calibration. The operation of the probe during the experiment, including its motions, are described. The primary experiment involved spectroscopic observation of the hot white dwarf HZ43. The photometer count rate is shown and the measurements of the diffuse background are compared with theoretical predictions. Despite the lower limits obtained using a narrowband detector, the measurements are not sensitive enough to draw any relevant astrophysical conclusions.
    Schlagwort(e): ASTRONOMY
    Materialart: (ISSN 0374-1958)
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  • 92
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    Five years of photometry of Sigma Geminorum (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Thirteen observatories have collaborated in obtaining five years of photoelectric photometry for the bright, K1 III RS CVn binary Sigma Geminorum. Except for one year, the light curve has exhibited two minima which are separated by approximately half a cycle. At the 1977.2 epoch of discovery one minimum was shallower, but as of 1982.2 they have become comparable in depth. During the 1979-80 season, the light curve changed shape rapidly, with the shallower minimum becoming as deep as the other within a period of no more than 80 days. The overall brightness range during the five years in V has been 4.13-4.29 mag, and it is found that the times of both minima can be fit with a photometric period of 19.423 days.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysics and Space Science (ISSN 0004-640X); 93; 2, Ju; June 198
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  • 93
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    Infrared (JHK) photometry of asteroids. II (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: JHK (1.2, 1.6, and 2.2 micron) photometry for 38 asteroids of various spectral classifications is reported. M asteroids tend to have infrared colors intermediate between the color domains of E and P asteroids. A few D asteroids have redder J - H colors than most C asteroids. The unusually red J - H color of 246 Asporina indicates it is a member of the A class.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; July 198
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  • 94
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    Massive eclipsing binary candidates (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: New UBV data are provided for 63 southern OB stars which are either identified in the survey by Garrison, Hiltner, and Schild as having double lines or are known from Wood et al. to be eclipsing binaries. Twenty of the stars are known eclipsing variables. Four stars, not previously known as eclipsing, have both spectroscopic evidence of duplicity and significant photometric variations. Several additional stars have a marginally significant spread in V magnitude.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 52; May 1983
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  • 95
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    Worldwide photometry and lightcurve observations of 16 Psyche during the 1975-1976 apparition (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Twenty-six lightcurves of Psyche are presented together with UBV photometry and phase functions from 1975 and 1976. Combining photometric data from this opposition with those from previous apparitions resulted in a mean phase coefficient in V of 0.026 + or - 0.002 mag/deg. No significant phase-dependent variation in the U-B color could be determined from the data; the B-V color, however, displayed a reddening with phase of 0.0010 + or - 0.0004 mag/deg. It is concluded that compositional variations over Psyche's surface are minor, and that Psyche's opposition effect is typical of that for other well-observed asteroids. Psyche's behavior is accounted for if, to the first order, its shape is that of a triaxial ellipsoid with axial ratios near 5:4:3.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 54; April 19
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    Worldwide photometry and lightcurve observations of 1 Ceres during the 1975-1976 apparition (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Lightcurves and UBV photometry of Ceres from the 1975-1976 apparition are presented. The synodic period is 0.37812 + or 0.00004 day, the mean absolute V magnitude is 3.61 + or 0.03, and the phase coefficient is 0.040 + or - 0.001 mag/deg. The U-B and B-V phase coefficients are +0.0015 + or - 0.0007 and +0.0006 + or - 0.0003 mag/deg, respectively. The colors at zero phase are B-V = +0.70 + or - 0.01 and U-B = +0.41 + or 0.01.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 54; April 19
    Format: text
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  • 97
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    Pole orientation of asteroid 44 Nysa via photometric astrometry, including a discussion of the method's application and its limitations (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The results of photometric astrometry, a method of determining the orientation of a rotation axis, as applied to asteroid 44 Nysa, are presented. The pole orientation of Nysa was found to be lambda(zero) = 100 deg, beta(zero) = +60 deg with an uncertainty of 10 deg. The sidereal period is 0.26755902 days + or - 0.00000006, and the rotation prograde. Refinements to, and limitations of, the application of the method of photometric astrometry are discussed. In light of the results presented herein, it is believed that all photometric astrometry pole determinations of the past should be redone.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 54; April 19
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  • 98
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    Lightcurves and phase function of asteroid 44 Nysa during its 1979 apparition (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Lightcurves of asteroid 44 Nysa obtained during 20 nights in 1979 as part of a global compaign are presented. The synodic period was 6 hours and 25.3 minutes. The phase coefficient of the primary maximum was 0.026 mag/deg and the absolute V magnitude 7.05. The phase function is linear from 2 to 25 deg, no opposition effect is present.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 54; April 19
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  • 99
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    Aperture synthesis observations of Orion B at 2.695 and 8.085 GHz (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Interferometer observations of Orion B at 2.695 and 8.085 GHz are presented. Orion B appears to be a double source: one H II region associated with the star NGC 2024 No. 2 and an extended H II region surrounding the star NGC 2024 No. 1. This structure gives support to the model that the stars NGC 2024 No. 2 and No. 1 (of spectral type O 9.5 and B 0.5, respectively) ionize the nebula.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 120; 2, Ap; April 19
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    Speckle imaging for planetary research (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The present study of speckle imaging technique effectiveness encompasses image reconstruction by means of a division algorithm for Fourier amplitudes, and the Knox-Thompson (1974) algorithm for Fourier phases. Results which have been obtained for Io, Titan, Pallas, Jupiter and Uranus indicate that spatial resolutions lower than the seeing limit by a factor of four are obtainable for objects brighter than Uranus. The resolutions obtained are well above the diffraction limit, due to inadequacies of the video camera employed. A photon-counting camera has been developed to overcome these difficulties, making possible the diffraction-limited resolution of objects as faint as Charon.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 53; March 19
    Format: text
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