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  • 1
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    Detection of silicates in the Beta Pictoris disk (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A broad 10-micron emission feature has been detected within 3 arcsec of the star Beta Pic which is known to have a circumstellar, possibly protoplanetary, disk. The observations were made using four narrow-band filters in the MSFC bolometer array at the IRTF. The emission feature closely resembles silicate features observed in Comets Halley and Kohoutek and in a variety of Galactic sources. The feature is strong, with the total flux density emitted by dust at 10.3 microns being at least twice the estimated continuum at that wavelength, and must be emitted by particles with characteristic radii less than 10 microns.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 372; L29-L31
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  • 2
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    Detection of the 3.4 micron emission feature in comets P/Brorsen-Metcalf and Okazaki-Levy-Rudenko (1989r) and an observational summary (1990)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: A survey was performed of the 3 micron spectral region of comets, including the broad 3.4 micron emission feature due to C-N bonds in organic molecules. One goal is to determine how the strength of the emission band varies with heliocentric distance r in comets. This depends on both the production rate of the organic molecules and the emission mechanism, neither of which is well determined at present. The observations to date are consistent with cometary organics being present in all comets at comparable abundances relative to water. Loss of contrast in the 3.4 micron feature as comets get closer to the sun is then easily explained by dilution by thermal emission from the continuum grains, whose flux rises more steeply with heliocentric distance than that of organics.
    Keywords: ASTROPHYSICS
    Type: Southwest Research Inst., Workshop on Observations of Recent Comets (1990); p 97-101
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  • 3
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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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  • 4
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    Observation of interstellar ammonia ice (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An absorption band probably due to solid ammonia on interstellar grains has been detected in the infrared spectrum at 2.97 microns of the Becklin-Neugebauer object and probably in NGC 2264-IR. An ammonia-water amorphous ice mixture can explain the structure of the new band and of the 3.07 microns interstellar absorption. Laboratory data suggest that a long wavelength wind extending to 3.5 microns in interstellar dust spectra may be absorption by NH3-H2O complexes in the ices. In the molecular cloud obscuring the BN object, about 20 times as much NH3 is frozen in grains as exists in the gas phase, suggesting the gas-grain interactions may be important in the ammonia chemistry of molecular clouds. Arguments are given that interstellar features at 6.0 and 6.8 microns are also ammonia-related absorptions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 260
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  • 5
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    Interstellar dust spectra between 2.5 and 3.3 microns - A search for hydrated silicates (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Spectra in the 2.5-3.3 micron wavelength region of VI Cyg 12, AFGL 2205, and AFGL 2885 were obtained in a search for bound water, hydroxyl groups, and hydrated minerals in interstellar dust. No new absorption bands were found. Comparison of expected strengths of bands of serpentine and chlorite-like minerals with the data suggests that less than 25 percent and 50 percent, respectively, of the silicate in the grains is composed of these materials.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 90; 1828-183
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  • 6
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    On the presence of phyllosilicate minerals in the interstellar grains (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The composition of the interstellar silicate dust is investigated. Condensation or alteration of silicate grains at temperatures of a few hundred degrees, in the presence of H2O, would result in hydrous or phyllosilicates, the silicate type most abundant in the type I carbonaceous chondrites. Infrared spectra of small particles (about 0.1 microns) of the high temperature condensates, olivine and pyroxene, at 300 K and 4 K do not give a good match to the interstellar absorption band near 9.8 microns. Laboratory spectra of several phyllosilicates give better agreement as does the spectrum of a carbonaceous chondrite. We propose that the silicates in the interstellar grains are predominantly phyllosilicates and suggest additional spectral tests for this hypothesis.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science; 35; June 197
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  • 7
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    Evidence for interstellar H2O in the Orion molecular cloud (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A search for interstellar gas phase H2O in the infrared spectrum of the BN object in Orion is reported. There is absorption (S/N = 2-4) at the position of the nu3 1(01)-2(02) line of H2O at 3801.42/cm, the strongest expected H2O line. Statistical analysis of the spectrum provides corroborating evidence for other H2O lines. With an assumed H2O excitation temperature of 150 K, N(H2O) of 2.3 x 10 to the 17th/sq cm or less toward the BN object is derived. The H2O column density implies abundance ratios of (H2O)/(CO) = 0.01-0.08 or less and (HDO)/(H2O) = 0.8-3.0 x 10 to the -3rd or more. The gas-to-ice ratio is (H2O gas)/(H2O ice) = 0.06 with an estimated uncertainty of a factor of 5.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 335; L27-L30
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  • 8
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    Water vapor in the Orion Molecular Cloud (1991)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Infrared observations of interstellar gas-phase H2O in the spectrum of the BN object in Orion are reported. There are absorptions (S/N = 2-5) at the positions of four of the strong lines in the 000-001 nu3 vibration-rotation band. With an estimated excitation temperature of 150 K, the column density of gaseous H2O toward BN in the OMC-1 cloud is (2 + or - 1) x 10 to the 17th/sq cm. The intensities of the lines imply an ortho/para ratio of 1 + or - 0.5 indicating recent sublimation of H2O from low-temperature grains. The results give gas-phase abundance ratios of H2O/CO roughly 0.03 + or - 0.02 and HDO/H2O = 0.001-0.0001 toward BN. The velocities of the H2O absorptions agree with those of the ridge source and CO outflow, but the position along the line of sight is not well constrained. The gas/solid ratio is H2O(gas)/H20(ice) = 0.05 or less. Less than 1 percent of the oxygen is in H2O gas (assuming total cosmic abundance). Most of the H2O in the line of sight to BN, and by inference in quiescent regions of molecular clouds generally, is frozen on grains.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 367; 162-167
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  • 9
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    An upper limit to the acetylene abundance toward BN in the orion molecular cloud (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A search for the acetylene (C2H2) nu3 infrared vibration-rotation absorption near 3 microns toward the Becklin-Neugebauer source in the Orion molecular cloud is reported. The relative abundance of C2H2/CO in the quiescent gas is less than 0.003.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 345; 265-267
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  • 10
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    Detection of the 3.4- and 2.8-micron emission features in Comet Bradfield (1987s) (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Comet Bradfield's 3.4-micron C-H emission feature at 3.4 microns, as well as the emission feature near 2.8 microns, exhibit spectral shapes similar to those noted in Comets Halley and Wilson; the derived abundances of the C-H bonds in all three comets are also comparable (within water production rate uncertainties). These data support the hypothesis that the species responsible for the 3.4- and 2.8-micron features may be common to all comets. Beyond this, the widely differing ages of the three comets suggest that the 3.4-micron feature-emitting organics are not the product of surface irradiation processes after the comets' formation.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 83; 434-440
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