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  • 1
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    Infrared spectroscopy and photometry of Comet Austin 1990 V (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: 3-micron and 10-micron spectra and IR photometry of the dynamically new Comet Austin 1990 V were obtained for March-May 1990. An unusual 9-11 micron emission feature 15-20 percent above the continuum is evident at 0.78 AU postperihelion. The shape, in particular a peak at 11.06 micron, differs from that seen in Halley and several other comets, suggesting a difference in the mineralogy of the silicate grains. The 3.1-7.7 micron spectrum at 0.35 AU shows no obvious feature; feature/continuum contrast of the 3.36 micron emission feature is less than about 5 percent. Based on the IR photometry and a dust model weighted toward small grains, the dust production rate on 6 May at 0.78 AU was about 3 x 10 exp 5 g/s. The corresponding dust/gas mass ratio was about 0.1, classifying Austin as a dust-poor comet. This designation refers only to the relative dust cross section, not to the total mass.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 101; 1; p. 64-70.
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  • 2
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    8-13 micron spectroscopy and IR photometry of Comet P/Brorsen-Metcalf (1989o) near perihelion (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Thermal IR spectrophotometry of Comet P/Brorsen-Metcalf near perihelion was obtained during August 28-September 6, 1989, by the NASA IRTF; these data are presently compared with results for Comet P/Halley. The spectra, which lacked silicate emission, are consistent with 400-430 K grey body emission. The grains are on these bases inferred to have been larger than typical for either new comets or P/Halley. Attention is given to the composition, mass, temperature, and character of the cometary dust in view of Comet P/Halley study results.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 97; 2, Ju; 269-275
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  • 3
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    8- to 13-micron spectroscopy of Comet Levy 1990 XX (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The results are reported of IR spectroscopy of Comet Levy 1990 XX over a three-day period when the comet was about 1.54 AU from the sun roughly 70 days before perihelion. Comet Levy 1990 XX was bright, and for at least part of its inbound journey toward perihelion, active. At a distance of 1.54 AU from the sun it showed strong structured silicate emission with peaks or shoulders at 9.8 and 11.2 microns. These features resemble those of Comets P/Halley and Bradfield 1987 XXIX. The comet was variable in brightness. Specifically, the contrast of the silicate features changed by a factor of two relative to the continuum level and showed some evidence for a shape change as well.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 100; 1; p. 197-202.
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  • 4
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    Forbidden lines of np(q) ions. II - Line intensities (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ground state forbidden transitions of np(q) ions of C, N, O, Ne, Mg, Si, S, and Fe can provide important information on the state of cosmic ionized gases. The line intensities of 95 transitions of these ions have been tabulated, including those used to calculate the line ratios as well as other strong lines of the ions in the ground state terms in the same temperature and density ranges treated previously. These data can be used for calculations of the absolute line intensities if the ionic abundances are known. These calculations are important for studies of the solar transition region, ionized nebulae, circumstellar nebulae such as found in symbiotic stars, supernova remnants, interstellar bubbles produced by stellar winds, and emission regions in active galactic nuclei.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 76; 1169-119
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  • 5
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    Silicates and variability in comets Okazaki-Levy-Rudenko (1989r) and Austin (1989c1) (1990)
    In:  Other Sources
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    Publication Date: 2013-08-29
    Description: Comet Okazaki-Levy-Rudenko (1989r) was studied over a wide range of wavelengths from the UV to the submillimeter. Using visual magnitude estimates from the IAU Circulars and reported submillimeter fluxes in conjunction with the thermal infrared spectroscopy and filter photometry, the nature of the grains and the behavior of the comet can be assessed and compared to other comets studied under this program. In addition, preliminary results from a collaborative infrared study of Comet Austin are presented which address the nature of the dust in that comet. Progress on a model for cometary properties and brightness behavior is discussed.
    Keywords: ASTROPHYSICS
    Type: Southwest Research Inst., Workshop on Observations of Recent Comets (1990); p 92-96
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  • 6
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    Comparison of P/Brorsen-Metcalf and P/Halley in the thermal infrared (1990)
    In:  Other Sources
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    Publication Date: 2013-08-29
    Description: Of the periodic comets, only comets Halley and Brorsen-Metcalf have periods of the order of 75 years and are bright enough to study spectroscopically in the infrared. Thermal IR spectroscopy of comet P/Brorsen-Metcalf near perihelion are presented and the results are compared to comet P/Halley.
    Keywords: ASTROPHYSICS
    Type: Southwest Research Inst., Workshop on Observations of Recent Comets (1990); p 70-74
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  • 7
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    Comets and the KAO (1995)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Seven comets have been observed from the Kuiper Airborne Observatory (KAO) in its twenty year history. Of these, comets p/Halley (1986 3) and Comet Wilson (1987 7) produced significant scientific results. Comet Halley was a bright and highly predictable comet that allowed a well-planned and coordinated observing program. Comet Wilson, on the other hand, was a dynamically new comet discovered only a few months before perihelion. In this paper we review the scientific discoveries made by the airborne program and the KAO on these comets, including the discovery of water, new structure in the silicate emission band, and a number of as yet unexplained spectral features.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Airborne Astronomy Symposium on the Galactic Ecosystem: From Gas to Stars to Dust, Volume 73; p 297-328
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  • 8
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    The 10 micron spectral structure in comets (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The 10 micron spectra of comets Halley (1982i), Wilson (1986l), Kohoutek (1973f) and Bradfield (1987s) are presented and compared. The silicate emission profiles of Halley and Bradfield are seen to be remarkably similar in that both contain a sharp break in the spectrum at 11.3 microns. Comet Bradfield does not show the same double peak structure seen in olivine and reported in Comet Halley be Campins and Ryan (1988) and Bregman, et al. (1987). The authors interpret the 11.3 micron signature as being due to olivine-type dust grains with at least some degree of crystallinity. Olivine alone is not enough to reproduce the shape of the 10 micron structure. However, in view of the authors' past success in fitting interstellar dust features with the emissivity profile obtained from amorphous grains produced by laser-vaporizing olivine, this is a very appealing identification. They note that there are significant variations in olivine spectra due to compositional differences, grain size distribution and related grain temperature variations to make the olivine identification tentative. They further tentatively identify the 9.8 micron feature in Halley as being due to either amorphorous olivine or a phyllosilicate (layer lattice). Neither the spectra of Halley, Kohoutek, nor Bradfield exhibited the 12.2 micron feature seen in Comet Wilson, which may prove diagnostic of the composition or thermal history differences between these comets. IR spectra of various mineral samples are discussed in terms of their match to cometary spectra.
    Keywords: ASTROPHYSICS
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 417-422
    Format: application/pdf
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  • 9
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    Pre-perihelion observations of Comet Halley at 2-13 microns (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Between Nov. 8, 1985 and Jan. 13, 1986 comet Halley brightness was obtained as a function of time at 2.3, 3.6, 4.6, and 10.3 microns. Brightness outbursts were noted, an especially significant one beginning Jan. 10, 1986 and persisting for several days during which the IR brightness more than doubled. The heliocentric brightness indices for 2.3, 3.6, 4.6, and 10.3 microns are -5.7, -7.1, -8.5, and -6.2, respectively. Comet Halley's absolute magnitudes at these wavelengths are 7.3, 4.4, 2.8, and -1.8. The 4.6 to 10.3 micron color temperature dependence on heliocentric distance (R) is slightly less steep than the Rsup -1/2 expected theoretically. The albedo of the comet is 8% to 9%. Based on spectral differences between outbursts on Nov. 8, 1985 and Jan. 10 to 13, 1986, it is concluded that the comet displays composition inhomogeneities.
    Keywords: ASTROPHYSICS
    Type: ESA, Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 3: Posters; p 479-484
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  • 10
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    Multiple aperture airborne infrared measurements of Comet Halley (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations at 10 microns with a 3.5' diameter beam made from the NASA Lear Jet Observatory during April 7.6 to 11.6, 1986 UT are presented. Data show evidence for a dramatic outburst (factor of 3 in 10 micron flux) with a turn-on time of 1 day and turn-off time of 1 to 2 days. Total mass ejected in the outburst is estimated. When combined with 8 and 10 microns data taken by Campins et al the dependence of the dust density on distance from the nucleus can be evaluated. It is shown that the flux within an aperture of diameter D is directly proportional to D well beyond 60" (2 million m at the comet). At 64 million m diameter (210"), the measurements are only 30% below the level expected for a strict F varies as d dependence. This, combined with the time scales of the event, places constraints on processes of grain destruction. The energy of the outburst is derived and compared to solar heating.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 2: Dust and Nucleus; p 125-128
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