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  • ASTRONOMY  (823)
  • SOLAR PHYSICS
  • 1985-1989  (588)
  • 1980-1984  (813)
  • 1970-1974  (52)
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  • 1
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    Observations of the J = 10 manifold of the pure rotational band of phosphine on Saturn (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Saturn was observed in the vicinity of the J = 10 manifold of the pure rotational band of phosphine on 1984 July 10 and 12 from NASA's Kuiper Airborne Observatory with the facility far-infrared cooled grating spectrometer. On each night observations of the full disk plus rings were made at 4 to 6 discrete wavelengths which selectively sampled the manifold and the adjacent continuum. The previously reported detection of this manifold is confirmed. After subtraction of the flux due to the rings, the data are compared with disk-averaged models of Saturn. It is found that PH3 must be strongly depleted above the thermal inversion (approx. 70 mbar). The best fitting models consistent with other observational constaints indicate that PH3 is significantly depleted at even deeper atmospheric levels ( or = 500 mbar), implying an eddy diffusion coefficient for Saturn of 10 to the 4 cm sq/sec.
    Keywords: ASTRONOMY
    Type: NASA-TM-86851 , REPT-85434 , PREPRINT-SER-042 , NAS 1.15:86851
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  • 2
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    Fast spectroscopic variations on rapidly-rotating, cool dwarfs. 3: Masses of circumstellar absorbing clouds on AB Doradus (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: New time-resolved H alpha, Ca II H and K and Mg II h and k spectra of the rapidly-rotating K0 dwarf star AB Doradus (= HD 36705). The transient absorption features seen in the H alpha line are also present in the Ca II and Mg II resonance lines. New techniques are developed for measuring the average strength of the line absorption along lines of sight intersecting the cloud. These techniques also give a measure of the projected cloud area. The strength of the resonance line absorption provides useful new constraints on the column densities, projected surface areas, temperatures and internal turbulent velocity dispersions of the circumstellar clouds producing the absorption features. At any given time the star appears to be surrounded by at least 6 to 10 clouds with masses in the range 2 to 6 x 10(exp 17) g. The clouds appear to have turbulent internal velocity dispersions of order 3 to 20 km/s, comparable with the random velocities of discrete filamentary structures in solar quiescent prominences. Night-to-night changes in the amount of Ca II resonance line absorption can be explained by changes in the amplitude of turbulent motions in the clouds. The corresponding changes in the total energy of the internal motions are of order 10(exp 29) erg per cloud. Changes of this magnitude could easily be activated by the frequent energetic (approximately 10(exp 34) erg) x ray flares seen on this star.
    Keywords: ASTRONOMY
    Type: NASA-CR-186563 , NAS 1.26:186563
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  • 3
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    A Far Infrared Echelle Spectrometer for the Kuiper Airborne Observatory (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-18
    Description: A liquid-helium-cooled grating spectrometer (CGS) is being developed as a facility instrument for the Kuiper Airborne Observatory (KAO), primarily to study for infrared lines originating in the interstellar medium. A maximum resolving power of approximately 6000 is achieved by means of a 45 cm long Echelle grating and is optically capable of operating in the spectral range from 25 to 300 microns. An array of detectors is used to simultaneously measure a line and the adjacent continuum from astronomical sources. Currently six detectors allow measurements in the 30 to 120 micron spectral band. The instrument, its operation, and its performance are described.
    Keywords: ASTRONOMY
    Type: Airborne Astron. Symp.; p 313-319
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  • 4
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    VLBI observations of a radio flare of Circinus X-1 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: VLBI 2.3 GHz observations of a strong radio flare of the binary star system Circinus X-1 indicate a radio source flaring component angular size of 0.0015-0.015 arcsec. This is equivalent to a linear size of 15-150 AU at the 10 kpc distance of Circinus X-1, although interstellar medium scattering may have enlarged the apparent angular source size. Since the radio source quiescent component, observed prior to the flare, had an angular size greater than 0.2 arcsec (equivalent to more than 2000 AU at 10 kpc), the quiescent radio emission comes from a region much larger than that proposed in recent models for Circinus X-1. The quiescent component appears to be variable on a time scale of years, and is probably fueled by the Circinus X-1 binary system.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 1
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  • 5
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    VLBI observations of the nucleus of Centaurus A (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: VLBI observations of the nucleus of Centaurus A made at 2.3 GHz on baselines with minimum fringe spacings of 0.15 and 0.0027 arcsec are presented. Results show that the nuclear component is elongated with a maximum extent of approximately 0.05 arcsec which is equivalent to a size of approximately 1 pc at the 5 Mpc distance of Centaurus A. The position angle of the nucleus is found to be 30 + or - 20 degrees, while the ratio of nuclear jet length to width is less than or approximately equal to 20. The nuclear flux density is determined to be 6.8 Jy, while no core component is found with an extent less than or approximately equal to 0.001 (less than or approximately equal to 0.02 pc) with a flux density of greater than or approximately equal to 20 mJy. A model of the Centaurus A nucleus composed of at least two components is developed on the basis of these results in conjunction with earlier VLBI and spectral data. The first component is an elongated source of approximately 0.05 arcsec (approximately 1 pc) size which contains most of the 2.3 GHz nuclear flux, while the second component is a source of approximately 0.0005 arcsec (approximately 0.01 pc) size which is nearly completely self-absorbed at 2.3 GHz but strengthens at higher frequencies.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 266
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  • 6
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    Far-IR spectroscopy of the galactic center: Neutral and ionized gas in the central 10 pc of the galaxy (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The 3P1 - 3P2 fine structure line emission from neutral atomic oxygen at 63 microns in the vicinity of the galactic center was mapped. The emission is extended over more than 4' (12 pc) along the galactic plane, centered on the position of Sgr A West. The line center velocities show that the O I gas is rotating around the galactic center with an axis close to that of the general galactic rotation, but there appear also to be noncircular motions. The rotational velocity at R is approximately 1 pc corresponds to a mass within the central pc of about 3 x 10(6) solar mass. Between 1 and 6 pc from the center the mass is approximately proportional to radius. The (O I) line probability arises in a predominantly neutral, atomic region immediately outside of the ionized central parsec of out galaxy. Hydrogen densities in the (O I) emitting region are 10(3) to 10(6) cm(-3) and gas temperatures are or = 100 K. The total integrated luminosity radiated in the line is about 10(5) solar luminosity, and is a substantial contribution to the cooling of the gas. Photoelectric heating or heating by ultraviolet excitation of H2 at high densities (10(5) cm(-3)) are promising mechanisms for heating of the gas, but heating due to dissipation of noncircular motions of the gas may be an alternative possibility. The 3P1 - 3P0 fine structure line of (O III) at 88 microns toward Sgr A West was also detected. The (O III) emission comes from high density ionized gas (n 10(4) cm(-3)), and there is no evidence for a medium density region (n 10(3) cm(-3)), such as the ionized halo in Sgr A West deduced from radio observations. This radio halo may be nonthermal, or may consist of many compact, dense clumps of filaments on the inner edges of neutral condensations at R or = 2 pc.
    Keywords: ASTRONOMY
    Type: NASA-CR-166510 , NAS 1.26:166510
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  • 7
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    Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. II - 207 sources (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Time delay and fringe frequency measurements at 2.29 GHz have been obtained with VLBI on baselines of about 10,000 km, in order to determine the positions of milliarcsec nuclei in 207 extragalactic radio sources. Accuracy ranges are estimated to lie between 0.1 and 1.0 arcsec in both right ascension and declination, with all sources having uncertainties of less than 4 arcsec in both coordinates. These sources constitute part of an all-sky VLBI catalog of milliarcsec radio sources, for 752 of which arcsec positions have thus far been determined.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 88; Aug. 198
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  • 8
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    Research in planetary astronomy and operation of the 2.2-meter telescope (1986)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The turn-around in the secular change in brightness of Pluto was detected, the planet is now beginning to brighten. The spectral signature was found of an ammonia bearing compound in the surface ices of Europa. Specific Io volcanic hotspots were detected from infrared photometry of the mutual events of the Jovian satellites. The polarized emission from the volcanic hotspots on Io was discovered and the locations of those hotspots were determined. The orbit of Charon was refined from speckle observations of the Pluto-Charon system. The spectral properties of liquid nitrogen-methane mixtures with reference to the infrared spectrum of Triton were studied. Major progress was made in modeling asteroid lightcurves from a modern theory of photometric properties of the asteroid surfaces. Several additional olivine-rich asteroids from near-infrared spectrophotometry were discovered. Important photometric, spectroscopic, narrow-band imaging data on Comet P/Halley was acquired, along with Schmidt photographs of Comet P/Halley and its tail.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 28-31
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  • 9
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    The project EGRET (Energetic Gamma-Ray Experiment Telescope) on NASA's Gamma-Ray Observatory (GRO) (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The design, predicted performance, and scientific objectives of the 20-30,000-MeV gamma-ray telescope EGRET for the NASA GRO spacecraft (scheduled for Space Shuttle launch to a 450-km 28.5-deg orbit in 1990) are reviewed. The other GRO instruments are briefly characterized, including the burst and transient-source experiment, the oriented scintillation spectrometer, and the imaging Compton telescope. EGRET comprises an anticoincidence system, a spark chamber, a triggering telescope, an NaI total-absorption spectrometer, a gas supply capable of refilling the chamber four times, and support electronics. EGRET will operate with energy resolution about 15 percent, effective area about 2000 sq cm, sensitivity about 5 x 10 to the -8th/sq cm sec, angular resolution 0.1-0.4 deg, and FOV about 40 deg FWHM. Observations of Galactic point sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, and solar flares are planned.
    Keywords: ASTRONOMY
    Type: Space Science Reviews (ISSN 0038-6308); 49; 1-2,
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  • 10
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    Solar wind-magnetosphere coupling and the distant magnetotail - ISEE-3 observations (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: ISEE-3 Geotail observations are used to investigate the relationship between the interplanetary magnetic field, substorm activity, and the distant magnetotail. Magnetic field and plasma observations are used to present evidence for the existence of a quasi-permanent, curved reconnection neutral line in the distant tail. The distance to the neutral line varies from absolute value of X = 120 to 140 R/sub e near the center of the tail to beyond absolute value of X = 200 R/sub e at the flanks. Downstream of the neutral line the plasma sheet magnetic field is shown to be negative and directly proportional to negative B/sub z in the solar wind as observed by IMP-8. V/sub x in the distant plasma sheet is also found to be proportional to IMF B/sub z with southward IMF producing the highest anti-solar flow velocities. A global dayside reconnection efficiency of 20 + or - 5 percent is derived from the ISEE-3/IMP-8 magnetic field comparisons. Substorm activity, as measured by the AL index, produces enhanced negative B/sub z and tailward V/sub x in the distant plasma sheet in agreement with the basic predictions of the reconnection-based models of substorms. The rate of magnetic flux transfer out of the tail as a function of AL is found to be consistent with previous near-earth studies. Similarly, the mass and energy fluxes carried by plasma sheet flow down the tail are consistent with theoretical mass and energy budgets for an open magnetosphere. In summary, the ISEE-3 Geotail observations appear to provide good support for reconnection models of solar wind-magnetosphere coupling and substorm energy rates.
    Keywords: SOLAR PHYSICS
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