The Shapes of the Circumstellar 'Silicate' Features,
Abstract
Around oxygen-rich stars we find that the spectra of most long-period variables (LPV) show an excess infrared emission which is attributed to circumstellar silicate dust grains. These grains produce emission features at about 10 and 18 micrometers 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 micrometers emission shows variations from star to star. With the availability of many IRAS Low Resolution Spectra (LRS) in the 9-22 micrometers region of M stars, we can now study the 10-micrometers feature to determine its uniformity (or lack thereof). For this analysis we assume that the 8-22 micrometers 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, we are left with a remaining strongly wavelength dependent emission feature which we call the excess silicate or 10 micrometers emission.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 08, 1986
- Accession Number
- ADA172017
Entities
People
- Irene R. Little-marenin
- Stephen D. Price
Organizations
- Air Force Research Laboratory