Title: Olivine mineralogy of young and evolved stars
Other Titles: Olivijn mineralogie van jonge en geëvolueerde sterren
Authors: de Vries, Bernard
Issue Date: 11-Sep-2013
Abstract: The spectral characteristics of crystalline olivine can be used as a probe of thephysical and chemical properties of circumstellar environments. In this thesisare presented the first Herschel Space Telescope observations of the 69 &#956;mband of crystalline olivine in the debris disk of ß Pictoris and the circumstellarenvironment of evolved stars. The observed 69 &#956;m band and other features of crystalline olivine are used todetermine the composition and location of the olivine crystals in the youngplanetary system of ß Pictoris. This analysis shows that the olivine crystals arepart of the collisional debris of relatively small (<10 km) comet-like planetesimalsorbiting in a Kuiper belt-like region of the planetary system. It is shown thatthe composition of the crystals is remarkably similar to those in comets of ourSolar System. A large set of Herschel/PACS observations of the 69 &#956;m band of crystallineolivine in the circumstellar environment of evolved stars is presented. Thissample consists out of many different types of evolved stars, among whichOH/IR stars, post-AGB stars and planetary nebulae. The 69 &#956;m bands of thesestars show that all these different types of evolved sources all produce the samepure magnesium-rich crystalline olivine. The OH/IR subsection of the large sample of Herschel/PACS observations isanalyzed in more detail. It is shown that the current and dense superwindof these objects has started no longer than 1200 years ago and that the dustin their outflows contains 2-14 % crystalline olivine (by mass). Depending onthe progenitor mass of the star the short time-scales that are found for thesuperwind causes a conundrum. The stars with a high mass progenitor starneed to go through several of these superwinds in order to lose enough massto leave the Asymptotic Giant Branch. Until now no such previously emittedsuperwinds have been detected as extended shells around such objects and thefurther evolution of these objects is not known.
Table of Contents: Abstract
1. Introduction
2. Comet-like mineralogy of olivine crystals in an extra-solar proto Kuiper belt
3. Determining the forsterite abundance of the dust around Asymptotic Giant Branch stars
4. Herschel/PACS observations of the 69 μm band of crystalline olivine around evolved stars
5. The problematically short superwind of OH/IR stars
6. Conclusions
7. Future prospects
Curriculum vitae
ISBN: 978-90-8649-646-4
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Institute of Astronomy

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