A TEMPORAL STUDY OF THE OXYGEN-RICH PULSATING VARIABLE ASYMPTOTIC GIANT BRANCH STAR, T Cep: INVESTIGATION ON DUST FORMATION AND DUST PROPERTIES

Pulsation is believed to be the leading cause of dusty mass loss from asymptotic giant branch stars. We present a temporal study of T Cep, a long-period Mira variable, using seven Infrared Space Observatory Short Wavelength Spectrometer spectra, covering a 16 month period over a single pulsation cycle. The observed spectral dust features change over the pulsation cycle of this Mira. In general, the overall apparent changes in spectral features can be attributed to changes in the dust temperature, resulting from the intrinsic pulsation cycle of the central star. However, not all feature changes are so easily explained. Based on direct comparison with laboratory spectra of several potential minerals, the dust is best explained by crystalline iron-rich silicates. These findings contradict the currently favored dust formation hypotheses.