A temporal study of oxygen-rich pulsating variable AGB star, T Cep: Investigation on dust formation and dust properties

TL;DR

This study analyzes how dust features in the spectrum of the Mira variable star T Cep change over a pulsation cycle, revealing that crystalline iron-rich silicates dominate dust composition, challenging existing formation theories.

Contribution

It provides the first detailed temporal spectral analysis of T Cep over a pulsation cycle, highlighting unexpected dust mineralogy that contradicts current models.

Findings

Spectral dust features vary with pulsation cycle.

Crystalline iron-rich silicates are the main dust component.

Observed dust properties challenge existing dust formation hypotheses.

Abstract

Pulsation is believed to be the leading cause of dusty mass loss from Asymptotic Giant Branch (AGB) stars. We present a temporal study of T Cep, a long-period Mira variable, using seven ISO SWS 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.