Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005sptz.prop20654c&link_type=abstract
Spitzer Proposal ID #20654
Astronomy and Astrophysics
Astronomy
Scientific paper
The evolution of stars on the Asymptotic Giant Branch (AGB) is characterized by substantial mass loss, producing large amounts of circumstellar dust and a dust-driven outflow, which injects the stellar ejecta into the interstellar medium. The composition of this newly formed dust is known to vary substantially from source to source, which is generally thought to reflect differences in the mass loss rate (e.g., density). During the evolution of the star on the AGB, the mass loss rate is known to vary substantially leading to large density variations and detached shell structures. Observations of bright examples of such shells provide us thus with the opportunity to dig into the past history of the mass loss processes from these objects. We propose to spectroscopically map the extended but bright outflow of the nearby AGB star, EP Aqr, with Spitzer-IRS from 5.2 -- 38 micron. In this way we will be able to trace the composition and mass of the dust formed at different times (e.g., corresponding to thousands of years of mass loss history). The IR spectrum of EP Aqr contains the spectral fingerprints of nearly all minerals (alumina, spinel, magnesium-iron oxides, amorphous and possibly crystalline silicates, gehlenite, ...) found in the dust shells surrounding O-rich AGB stars, which makes it an ideal target for such a dust astro-archeology study. The proposed observations will therefore directly link for the first time the spectral differences in dust composition to the mass loss history of the central star. Such observations will also provide important clues to large-scale structure of AGB star outflows as well as to theoretical models for dust formation and mass-loss mechanisms.
Cami Jan
Peeters Els
Tielens Xander
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