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thesis - IRS, The Infrared Spectrograph

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Contents1 Introduction 11.1 Evolution of low and intermediate mass stars . . . . . . . . . . . . . . . . 21.1.1 From the cradle to the grave . . . . . . . . . . . . . . . . . . . . . 21.1.2 Nucleosyn<strong>thesis</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1.3 Mixing episodes during the evolution . . . . . . . . . . . . . . . . 31.2 Planetary Nebulae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.2.1 PNe and the chemical enrichment of the ISM . . . . . . . . . . . . 41.2.2 Importance of PNe . . . . . . . . . . . . . . . . . . . . . . . . . 51.2.3 Neutral material around PNe . . . . . . . . . . . . . . . . . . . . 51.2.4 PNe in a general context . . . . . . . . . . . . . . . . . . . . . . . 61.3 Physics in PNe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3.1 <strong>The</strong> spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3.2 Electron density and temperature, and abundances . . . . . . . . . 81.4 Studying PNe in the infrared . . . . . . . . . . . . . . . . . . . . . . . . . 101.5 In this <strong>thesis</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 <strong>The</strong> ISO–SWS Spectrum of Planetary Nebula NGC 7027 132.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.2 ISO observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.3 Data reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.4 Line flux discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.5 <strong>The</strong> visual and the ultraviolet spectrum . . . . . . . . . . . . . . . . . . . 182.6 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.6.1 Electron density . . . . . . . . . . . . . . . . . . . . . . . . . . . 212.6.2 Electron temperature . . . . . . . . . . . . . . . . . . . . . . . . 222.6.3 Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.7.1 Missing stages of ionization . . . . . . . . . . . . . . . . . . . . . 262.7.2 Physical parameters . . . . . . . . . . . . . . . . . . . . . . . . . 272.7.3 Abundances with recombination lines . . . . . . . . . . . . . . . . 272.7.4 Abundances and progenitor . . . . . . . . . . . . . . . . . . . . . 282.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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