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  • 1
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    Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Overview and spectral characteristics (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Large-amplitude electromagnetic plasma waves are one of the dominant features of the solar wind-comet interaction. Wave characteristics strongly depend on parameters such as the solar wind flow and Alfven velocities and the angle between flow and interplanetary magnetic field as well as the production rate. With respect to the latter the flyby of the spacecraft Giotto at comet P/Griff-Skjellerup provides a unique possibility to study such waves in further detail. Pickup ion-related wave signatures have been observed up to a distance of 600,000 km from the nucleus. Peak spectral power in the spacecraft frame of reference occurs at frequencies mainly somewhat below the water group ion gyrofrequency. From this the waves are determined to be mainly left-hand polarized waves, causing one-sided pitch angle diffusion outbound. The wave activity strongly increases close to the comet; upstream it exhibits a quadratic dependence on the water group pickup ion free energy. Furthermore, a phenomenological study of the wave characteristics provides a unique description of the fine-structure of the interaction region. Indications of steepened magnetosonic waves have been found in the outbound magnetosheath region.
    Keywords: ASTRONOMY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A12; p. 20,921-20,935
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  • 2
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    A radiation belt monitor for the High Energy Transient Experiment Satellite (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: A Radiation Belt Monitor (RBM) sensitive to protons and electrons with energy approximately greater than 0.5 MeV has been designed for the High Energy Transient Experiment (HETE) satellite in order to: first, control the on-off configuration of the experiments (i.e. those susceptible to proton damage); and second, to indicate the presence of proton and/or electron events that could masquerade as legitimate high energy photon events. One of the two RBM channels has an enhanced sensitivity to electrons. Each channel of the RBM, based on a PIN silicon diode, requires a typical power of 6 milliwatts. Tests have been performed with protons with energies from approximately 0.1 to 2.5 MeV (generated by a Cockcroft-Walton linear accelerator via the d(d,p)t reaction), and with electrons with energies up to 1 MeV (from a 1.0 microcurie Bi-207 source).
    Keywords: ASTRONOMY
    Type: Experimental Astronomy (ISSN 0922-6435); 4; 1; p. 59-75
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  • 3
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    Cataclysmic variables and related objects (1993)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: This volume begins with an introductory chapter on general properties of cataclysmic variables. Chapters 2 through 5 of Part 1 are devoted to observations and interpretation of dwarf novae and nova-like stars. Chapters 6 through 10, Part 2, discuss the general observational properties of classical and recurrent novae, the theoretical models, and the characteristics and models for some well observed classical novae and recurrent novae. Chapters 11 through 14 of Part 3 are devoted to an overview of the observations of symbiotic stars, to a description of the various models proposed for explaining the symbiotic phenomenon, and to a discussion of a few selected objects, respectively. Chapter 15 briefly examines the many unsolved problems posed by the observations of the different classes of cataclysmic variables and symbiotic stars.
    Keywords: ASTRONOMY
    Type: NASA-SP-507 , NAS 1.21:507 , LC-92-7619 , QB835.H27
    Format: application/pdf
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  • 4
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    The quality of photometric information in the Hipparcos Input Catalog (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Comparison with independent photoelectric photometry is used to assess the quality of magnitudes and colors in the Hipparcos Input Catalog. These magnitudes and colors will play an important role in the luminosity calibration of Hipparcos stars. We conclude that photoelectric photometry, available for about 37 percent of the catalog, is of uniformly good quality, and the error estimates in the Catalog are very accurate. On the other hand, colors determined from poor spectral classes suffer from very significant errors, also correctly estimated in the Catalog, which make them essentially unsuited for the purpose of luminosity calibration. Only stars with either photoelectric colors or good 2D spectral classes can be used in a high-accuracy luminosity calibration.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 105; 6; p. 2344-2352.
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  • 5
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    Discovery of the candidate Kuiper belt object 1992 QB1 (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The discovery of a new faint object in the outer solar system, 1992 QB1, moving beyond the orbit of Neptune is reported. It is suggested that the 1992 QB1 may represent the first detection of a member of the Kuiper belt (Edgworth, 1949; Kuiper, 1951), the hypothesized population of objects beyond Neptune and a possible source of the short-period comets, as suggested by Whipple (1964), Fernandez (1980), and Duncan et al. (1988).
    Keywords: ASTRONOMY
    Type: Nature (ISSN 0028-0836); 362; 6422; p. 730-732.
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  • 6
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    The laboratory spectrum of acetaldehyde at 1 millimeter (230-325 GHz) (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The rotational spectrum of acetaldehyde (CH3CHO) in the frequency range 230-325 GHz has been measured in the laboratory using millimeter/submillimeter direct absorption spectroscopy. Over 250 transition frequencies are presented for this molecule for both A and E symmetry species in its ground (upsilon(sub t) = 0) and first excited (upsilon(sub t) = 1) torsional state, with experimental uncertainties of +/- 50 kHz. The data were fitted with a model involving an internal rotation potential function, which typically reproduces the measured frequencies to nu(sub obs) - nu(sub calc) less than or approximately 50 kHz for both ground and upsilon(sub t) = 1 state. These newly measured rest frequencies should aid in the identification of interstellar CH3CHO and in spectral line assignments for millimeter-band scans.
    Keywords: ASTRONOMY
    Type: The Astrophysical Journal Supplement Series (ISSN 0067-0049); 89; 1; p. 221-226
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  • 7
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    A degree scale anisotropy measurement of the cosmic microwave background near the star Gamma Ursae Minoris (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Results from a search for anisotropy in the cosmic microwave background (CMB) are presented from the third flight of the Millimeter-wave Anisotropy experiment. The CMB observation occurred over 1.37 hours and covered a 6.24 sq deg area of the sky where very little foreground emission is expected. Significant correlated structure is observed at 6 and 9/cm. At 12/cm we place an upper limit on the structure. The relative amplitudes at 6, 9, and 12/cm are consistent with a CMB spectrum. The spectrum of the structure is inconsistent with thermal emission from known forms of interstellar dust. Synchrotron and free-free emission would both require unusually flat spectral indices at cm wavelengths in order to account for the amplitude of the observed structure. Although known systematic errors are not expected to contribute significantly to any of the three optical channels, excess sidelobe contamination cannot be definitively ruled out. If all the structure is attributed to CMB anisotropy, a value of the weighted rms of the 6 and 9/cm channels of Delta T/T(CMB) = 4.7 +/- 0.8 x 10 exp -5 (+/- 1 sigma) was measured. If the CMB anisotropy is assumed to have a Gaussian autocorrelation function with a coherence angle of 25 arcmin, then the most probable value is Delta T/T(CMB) = 4.2 +1.7 or -1.1 x 10 exp -5, where the +/- refers to the 95 percent confidence limits.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 413; 1; p. L1-L5.
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  • 8
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    Radio observations of the remnant of the supernova of AD 1006. II - Polarization observations (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Polarized flux observations of the SNR of AD 1006 made with the NRAO VLA are presented. The gross morphology in polarized intensity reveals two bright limbs across from each other. The SE quadrant, faintest in total intensity, shows significant polarized flux, while the extension of the NE, fairly bright in total intensity, appears almost unpolarized. Significant polarized flux is also seen in the SNR center. An integrated polarized fraction of about 13 percent is found; ratios as high as 30 percent may occur locally. The observations can be used to infer an intrinsic polarization position angle, and it is deduced that the ordered component of the magnetic field is primarily radial. The polarized fraction upper limits imply that the magnetic field is dominantly disordered, and it is estimated that the radial component contains only about 20 percent of the total magnetic energy density.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 106; 1; p. 272-283.
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  • 9
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    The OB associations of 30 Doradus in the Large Magellanic Cloud. I - Stellar observations and data reductions (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: UBV photometry is presented for 2400 stars in the OB associations of 30 Doradus in the Large Magellanic Cloud, and I discuss new spectroscopic observations of 54 stars including 24 O stars. The CCD fields cover an area of 50 square arcminutes in the central region. The entire catalog (exclusive of the dense core cluster R 136) is photometrically complete to V = B = 18 mag and U = 17 mag, although the completeness magnitudes are fainter for regions with less nebular contamination.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 106; 2; p. 560-577, 821-823.
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  • 10
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    An improved ultraviolet spectral line list for the symbiotic star RR Telescopii (1993)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: We have remeasured wavelengths and intensities of International Ultraviolet Explorer (IUE) spectra of the symbiotic star, RR Tel. The main work is centered on the long 820 minute exposure high-resolution spectrum obtained on 1983 June 18. The list is intended to serve as a source of improved intensities and wavelengths for the ultraviolet spectrum of this star. A complete line list with intensities based on this exposure has not been published previously. The strongest spectral lines are saturated in the 820 minute exposure, and intensities for these lines are mostly obtained from a 20 minute exposure obtained on the same day. A few intensities are obtained from other exposures if neither the 820 nor the 20 minute exposure is satisfactory. There are 111 lines in our list between 1168 and 1980 A. Some of the very weakest lines may not be real. These are indicated by question marks. We also discuss some of the plasma diagnostics available using spectral lines of O v and O iv.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 87; 1; p. 331-336.
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