A model is developed to describe radiative transfer in a spherical dust envelope that is employed to examine IRAS point-source data. A generalized two-stream Eddington-approximation approach is taken, and various combinations of the mass-loss rate, condensation temperatures of the dust grains, and elapsed times from the inception of mass loss are used for calculations. The IRAS data, taken from M stars which emit in the 10-micron silicate band and demonstrate good characteristic 12-, 25-, and 60-micron fluxes, provide the variables for the calculations. The 10-micron emission band is demonstrated to be a direct indicator of the mass-loss rate, and the range of rates is given for M stars. Steady mass loss in these stars lasts about 2000 years, and the condensation temperature of the dirty silicate grains is found to be approximately 900 K. The IRAS data agree with the model predictions particularly well when the opacity of the grains is proportional to lambda exp -1.5 for wavelengths over 28 microns.
From Miras to Planetary Nebulae: Which Path for Stellar Evolution?
- Pub Date:
- Astronomical Models;
- Emission Spectra;
- M Stars;
- Color-Color Diagram;
- Infrared Astronomy Satellite;
- Stellar Mass Ejection;