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  • 1
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    Infrared observations of Comet Austin (1990 V) by the COBE/Diffuse Infrared Background Experiment (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Comet Austin was observed by the Cosmic Background Explorer (COBE)/Diffuse Infrared Background Experiment (DIRBE) with broadband photometry at 1-240 micrometers during the comet's close passage by Earth in 1990 May. A 6 deg long (6 x 10(exp 6) km) dust tail was found at 12 and 25 micrometers, with detailed structure due to variations in particle properties and mass-loss rate. The spectrum of the central 42 x 42 sq arcmin pixel was found to agree with that of a graybody of temperature 309 +/- 5 K and optical depth 7.3 +/- 10(exp -8). Comparison with IUE and ground-based obervations indicates that particles of radius greater than 20 micrometers predominate by surface area. A mass-loss rate of 510 (+510/-205) kg/s and a total tail mass of 7 +/- 2 x 10(exp 10) kg was found for a model dust tail composed of Mie spheres with a differential particle mass distribution dn/d log m approx. m(exp -0.63) and 2:1 silicate:amorphous carbon composition by mass.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 432; 1; p L71-L74
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  • 2
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    Characteristics of the persistent emission of SGR 1806-20 (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Earlier, using the X-ray satellite ASCA, we had identified the soft gamma-ray burst repeater (SGR) 1806-20 with a persistent X-ray source, AX 1805.7-2025 which is located close to the center of the radio supernova remnant G10.0-0.3. A burst seen by Burst and Transient Source Experiment (BATSE) was shown to be centered on G10.0-0.3. Here we report detailed temporal and spectral analysis of the persistent source. We find that AX 1805.7-2025 is a very compact source, size less than 30 sec in diameter, with a power-law spectrum. The count rate from AX 1805.7-2025 is steady on timescales of minutes, days, and 1 week. Most supernova remnants have extended X-ray emission ascribed to shocked gas. We set an upper limit to an extended X-ray emission both in continuum and line emission. We conclude that an isolated neutron star, most likely a pulsar, powers the radio remnant G10.0-0.3. Finally, we note that the persistent spectrum appears to be less absorbed than the burst spectrum.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 436; 1; p. L23-L25
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  • 3
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    A sensitive upper limit on the methane abundance in Comet Levy (1990c) (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are presented on a ground-based search for fluorescent emission from CH4 at 3.3 microns in a newly discovered long-period comet, Comet Levy (1990c). It was found that the upper limit to the CH4 abundance in Comet Levy is similar to the Comet Halley CH4 abundance estimated from lower resolution IR spectra by Kawara et al. (1988). The Comet Levy CH4 abundance is significantly lower than the abundance derived by Larson et al. (1989) from a possible detection of CH4 in Comet Wilson.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 372; L113-L11
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  • 4
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    Comparison of magnetosonic wave and water group ion energy densities at Comet Giacobini-Zinner (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the Comet Giacobini-Zinner (GZ) are presented to determine to what extent wave-particle scattering redistributed the initial pick-up energy of the ion population. Also examined is the difference between the ion thermal energy and the energy in the magnetic fields of the waves. In spite of uncertainty of about a factor of 2 noted in the pick-up and mass-loaded regions, it is shown that less than approximately 50 percent of the pick-up energy is converted into wave magnetic energy in the inbound pick-up region.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 11; 9, 19; 83-86
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  • 5
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    A strong 3.4 micron emission feature in comet Austin 1989c1 (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High resolution 2.8-4.0 micron spectra of the 'new' comet Austin 1989c1, taken on 15-16 May 1990 confirm the presence of the broad emission features around 3.4 and 3.52 micron seen in a number of bright comets and ascribed to organic material. Both the 3.4 micron band strength and the 3.52/3.36 micron flux ratios are among the largest so far observed. The data are consistent with the relationship between band strength and water production rate that was recently derived. Excess emission at 3.28 and 3.6 micron cannot be unambiguously identified as features due to the poor signal-to-noise ratio.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Asteroids, Comets, Meteors 1991; p 211-214
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  • 6
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    Limit on the CH4/CO ratio in Comet Levy (1990c) and comparisons with other comets (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Near-infrared observations of comet Levy (1900c) were made on UT 4.3 and 5.3 Sep. 1990 from the United Kingdom Infrared Telescope on Mauna Kea. A scanning Fabry-Perot interferometer in combination with a cooled grating spectrometer was used to make a sensitive search for fluorescent emission from the v zub 3 band of CH4 near lambda approx. 3.3 microns. If CH4 is a parent molecule released directly from the nucleus, then the 3 sigma limit on its abundance is CH4/H2O approx. less than 0.0031, assuming that the kinetic temperature of the inner coma is approx. 50 K and that the CH4 spin species are equilibrated at a temperature approx. greater than 50 K. Since International Ultraviolet Explorer (IUE) observations of CO in Levy indicate that CO/H2O approx. 0.04 (Feldman et al.), researchers find that CH4/CO approx. less than 0.1. Infrared spectroscopic searches for CH4 in Comet Halley also yielded no positive detections; the more sensitive upper limit from the latter observations is CH4/H2O approx. less than 0.002. Since CO/H2O approx. 0.05 in Halley (not including the extended source of CO), the upper limits on the CH4/CO ratios are almost identical for comets Levy and Halley. A marginal infrared detection of the CH4 v sub 3 band in comet Wilson yielded CH4/H2O approx. 0.01 to 0.05 (Larson et al.), but there was no positive detection of CO. If the identification of the feature in the infrared spectrum of comet Wilson is correct, then that would indicate a very high CH4/CO ratio in this comet.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Abstracts for the International Conference on Asteroids, Comets, Meteors 1991; p 233
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  • 7
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    New observations of the cyclotron absorption feature in Hercules X-1 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Ginga satellite observatory has been used to measure a cyclotron feature in the hard X-ray spectrum of the 1.24-s binary pulsar Hercules X-1 with a much greater energy resolution than in previous observations. The spectrum from 10-60 keV can be described with a simple analytical formula which indicates an absorption feature at about 34 keV rather than an emission feature at about 50 keV. From this, the surface magnetic field strength of Her X-1 is estimated to be (2.9 + or - 0.3) x 10 to the 12th G.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 346; 250-252
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  • 8
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    More interstellar emission features at 3.3-3.6 micrometers! (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The present data set consists of 3.20 to 3.55 micron spectra of HD44179, NGC 7027, BD+30 3639, and Elias 1 obtained with a cooled-grating array spectrometer (CGAS) at the NASA Infrared Telescope Facility. Emission features and details of the emission feature profiles are presented for high resolution spectra. Greater complexity is shown than might be expected. It is significant that the 3.29 micron feature has an invariant central wavelength, even at high resolution, and this strongly supports the case for a very specific substance or mixture of substances which is giving rise to this feature.
    Keywords: ASTROPHYSICS
    Type: NASA. Ames Research Center Summer School on Interstellar Processes: Abstracts of Contributed Papers; p 115-116
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  • 9
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    Ground-based detection of water in Comet Halley (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Gaseous water was detected in the coma of comet Halley. Emission was observed in the upsilon 1 + upsilon 3 band at 1.4 microns, and the upsilon 2 + upsilon 3 band at 1.9 microns. Based on the upsilon 1 + upsilon 3 band intensity, the mass loss rate is 2 times 10 to the 29th power molecules/sec (with an uncertainty of a factor of 2) on 29 Oct. 1985, marginally consistent with other detections. The method is applicable to observations of H2O in other fast-moving comets.
    Keywords: ASTROPHYSICS
    Type: ESA, Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 3: Posters; p 99-101
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  • 10
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    A high resolution far-infrared survey of a section of the galactic plane. II - Far-infrared, CO, and radio continuum results (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An area of 7.5 sq deg of the galactic plane at 70 microns have been surveyed with a 1-arcmin beam. The region lies between lII equals 10 deg and lII equals 16 deg and includes the M17 and W33 complexes. The weakest of the 42 sources detected had a flux density of 350 Jy at 70 microns. Detailed far-infrared, (C-12)O, (C-13)O, and radio continuum observations of the sources are presented. The derivation of the important physical parameters of the sources and their surrounding molecular clouds are discussed. The properties of the individual regions are also discussed and maps of selected sources are presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 48; Jan. 198
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