UvA-DARE (Digital Academic Repository) Crystalline silicates in circumstellar dust shells Molster, F.J. Link to publication

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1 UvA-DARE (Digital Academic Repository) Crystalline silicates in circumstellar dust shells Molster, F.J. Link to publication Citation for published version (APA): Molster, F. J. (2000). Crystalline silicates in circumstellar dust shells General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam ( Download date: 14 Feb 2017

2 Contents 1 Introduction General introduction The evolution of solar-type stars The evolution of dust in the interstellar medium The study of dust The infrared spectroscopy of dust Amorphous versus crystalline Laboratory measurements of cosmic dust analogues Infrared Space Observatory Crystalline silicates Crystalline silicates and the evolution of dust Outline of this thesis 16 2 Steps toward interstellar silicate mineralogy: IV. The crystalline revolution Introduction Structure of crystalline silicates Synthesis and analytical characterization of the samples Spectroscopy Olivines Pyroxenes Correlation between band shifts and Fe content Optical data of enstatite Non-homogeneous samples Discussion 35 3 The composition and nature of the dust shell surrounding the binary AFGL Introduction The observations and data reduction ISO observations fxm imaging at the ESO 3.6m telescope The /jm part of the spectrum; A binary revealed Interstellar and circumstellar extinction 53 v

3 3.4 The firn part of the spectrum; The dust shell The continuum subtraction of the SWS and LWS spectra Identifications Radiative transfer modelling Dust species The best fit model parameters Discussion of the model fit Discussion The distance and luminosity The dust shell Formation of crystalline silicates Conclusions 75 4 The complete ISO spectrum of NGC Introduction The observations and data reduction The dust features The fjm region; C-rich dust The fim region; an uncertain area of the spectrum The /vm region; O-rich dust Modelling Discussion 88 5 IRAS : A carbon star surrounded by highly crystalline silicate dust Introduction The Observations Modelling Discussion The underlying carbon star The cool silicate dust The evolutionary status of IRAS The crystalline dust Conclusions Low-temperature crystallization of silicate dust in circumstellar disks Introduction Crystalline silicates around evolved stars Crystallinity versus large grains The origin of the high crystallinity Low temperature crystallization Overview of crystalline silicate dust around stars Introduction The observations and data reduction The sample 115 VI

4 7.2.2 Data reduction H Thecontinua Mean spectra Method of measurement Results for the complexes micron complex (7-13 /im) micron complex (15-20 >im) micron complex ( /im) micron complex ( pm) micron complex ( /mi) micron complex ( pm) micron complex (50-72/im) Remaining features Identification Laboratory measurements of crystalline silicates micron complex (7-13 fim) micron complex (15-20/im) micron complex ( /im) micron complex ( /im) micron complex ( /zm) micron complex ( /im) micron complex (50-72/im) Remaining features The sample stars Disk-sources Outflow sources Discussion and conclusions Appendix; Notes on individual stars A correlations study of crystalline silicate features Introduction Trends in the bandwidth and position The peak position The bandwidth The modelling The sample stars Correlations Temperature dependence of lab spectra: peak width and position Other temperature trends Abundance trends Crystallinity versus stellar flux ratio Discussion Conclusions 257 vii

5 9 Summary and Outlook General summary Outlook Nederlandse samenvatting Een stoffige studie Algemene inleiding Verschillende soorten stof Gestructureerd stof De bestudering van stof De ontdekking van ISO Het onderzoek beschreven in dit proefschrift 270 Abbreviations 275 Dankwoord 277 vin