Shapes of the circumstellar silicate features

Technical Report · Mon Sep 08 04:00:00 EDT 1986

OSTI ID:7106431

Little-Marenin, I R; Price, S D

Around oxygen-rich stars, spectra of most long-period variables (LPV) show an excess infrared emission that is attributed to circumstellar silicate dust grains. These grains produce emission features at about 10 and 18-..mu..m due to bending and stretching modes of Si0, respectively. It has been known (Forrest, Gillett and Stein 1975) that the spectral energy distribution of the 10-..mu..m emission shows variations from star to star. With the availability of many IRAS Low Resolution Spectra (LRS) in the 9-22-..mu..m region of M stars, the 10-..mu..m feature was studied to determine its uniformity (or lack thereof). For this analysis, it was assumed that the 8-22-..mu..m emission from these stars is produced by a) the stellar photosphere, b) a continuum emission from the dust grains, and c) a strongly wavelength-dependent dust grain emission term. By representing the first two terms with blackbody energy distributions and subtracting them from the observed spectrum, remaining is a strongly wavelength-dependent emission feature called the excess silicate or 10-..mu..m emission.

• Research Organization: Air Force Geophysics Lab., Hanscom AFB, MA (USA)
• OSTI ID: 7106431
• Report Number(s): AD-A-172017/6/XAB; AFGL-TR-86-0183
• 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
ATMOSPHERES
BLACKBODY RADIATION
COSMIC DUST
DUSTS
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION SPECTRA
INFRARED SPECTRA
INTERSTELLAR GRAINS
NONMETALS
OXYGEN
OXYGEN COMPOUNDS
PARTICLES
PHOTOSPHERE
RADIATIONS
SILICATES
SILICON COMPOUNDS
SOLAR ATMOSPHERE
SPECTRA
STARS