SILICATES IN EVOLVED STARS - THE LRS-MASER CHRONOLOGY REVISITED

Since the publication of our correlation (1990 Ap.J. 350, L45) suggest ing a temporal relationship among: (a) shapes of 10 micron silicates s een in IRAS Low Resolution Spectra (LRS); (b) IRAS broad band colors; (c) light curve asymmetries, and (d) the types of masers associated wi th Various Mira variable stars, the question has arisen whether the im plied chronology refelcts the interval between thermal pulses, or the more lengthy ascent of the AGE. There is evidence in favor of the form er interpretation. A strong implication of this idea is that variabili ty among pre-silicate spectra should be significant. Several examples of this have been found in the extended LRS database, and are presente d. Finally, plans are presented to continue monitoring of selected Var iables in the 10 micron region, to verify the variability suggested in the limited phase coverage provided in the LRS database. Monitoring w ill include use of our facilities at the Mt.Evans-Womble Observatory - highest in the world at 4313 meters altitude.