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  • 1
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    The Carbon-Rich Dust Sequence: Infrared Spectral Classification of Carbon Stars (1997)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We have developed a classification system for the infrared spectral emission from carbon stars, using a sample of 96 bright carbon-rich variables associated with the asymptotic giant branch. In addition to the stellar contribution, most spectra include the 11.2 micron emission feature from SiC and either a smooth cool continuum from amorphous carbon or a secondary emission feature at 9.0 microns. We have identified a carbon-rich dust sequence along which the amorphous carbon component grows while the 9.0 micron feature declines in strength. Along this spectral sequence, the fraction of Miras increases, as does the period of variability, the mass-loss rate, and the thickness of the circumstellar shell. Thus the carbon-rich dust sequence appears to be an evolutionary sequence. One class of spectra shows a particularly strong 9.0 micron feature, Enhanced C/O ratio, and several other unusual properties that suggest a different sequence, perhaps related to J stars.
    Keywords: Space Radiation
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    A Search for Structure in PAH Emission in Extended Sources at 3.3 and 3.4 Microns (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We have observed three extended sources of the infrared emission features associated with polycyclic aromatic hydrocarbons (PAHs), using a 128x128 InSb array mounted on the 1.5 m NASA/Steward telescope on Mt. Lemmon. We used a CVF (1.5% bandpass) to isolate the emission from the 3.29 and 3.40 microns PAH features in NGC 1333 #3, Sharpless 106, and the Orion Bar. In all three sources, the 3.29 and 3.40 microns emission features arise from the same regions, but show decidedly different structure. We are analyzing the images to determine the relationship of the 3.40 microns feature to the main feature at 3.29 microns. The 3.40 microns feature may be a vibrational overtone of the 3.29 microns feature, or it may arise from attached molecular sidegroups.
    Keywords: Space Radiation
    Type: 185th AAS Meeting; Jan 08, 1995 - Jan 13, 1995; Tucson, AZ; United States
    Format: text
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    NASA TECHNICAL REPORTS
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