IRAS low-resolution spectral observations of the 10 and 18 micron silicate emission feature

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/169721· OSTI ID:5702414

Simpson, J P ^[1]

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1. California Univ., Berkeley (USA)

The IRAS LRS Atlas contains 8-23 micron spectra of 1816 stars with silicate emission features. In order to study the shapes of the silicate dust features, the 117 stars whose emission features appear to be optically thin and which have the best signal-to-noise ratio at the longest wavelengths were analyzed. Simple spherical dust shell models were calculated in both the optically thin and the slightly optical thick approximations. From the comparison of the predicted spectra of the dust and stellar continuum, the emissivity function Kappa(lambda) was derived. In the different stars, the shape of the 10-micron feature is either narrow or broad and it is peaked either at about 9.7 microns or at 10 microns. Either particle size effects (particles above 0.75 microns in radius) or optical depth effects (central optical depth about 1) could broaden the 10-micron feature. Chemical composition differences no doubt are also important, particularly as regards the position of the peak of the 10-micron feature. The stars with the peak at 10 microns are more closely confined to the Galactic plane than the stars with the peak at 9.7 microns. The shape of the 18-micron feature is essentially the same in all stars, and can be used to extend the interstellar extinction curve past 13 to 22 microns. 51 refs.

• OSTI ID: 5702414
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 368; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
COSMIC DUST
DUSTS
EMISSION SPECTRA
INFRARED SPECTRA
INTERSTELLAR SPACE
LINE WIDTHS
MATHEMATICAL MODELS
OXYGEN COMPOUNDS
PARTICLE SIZE
SATELLITES
SIGNAL-TO-NOISE RATIO
SILICATES
SILICON COMPOUNDS
SIZE
SPACE
SPECTRA
STAR MODELS
STARS