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THE CIRCUMSTELLAR MEDIUM OF AGB STARS: A study of scattered stellar light and

THE CIRCUMSTELLAR MEDIUM OF AGB STARS: A study of scattered stellar light and molecular radio line emission. PART I : A study of episodic mass loss: The detached shells of some AGB stars seen in scattered stellar light. PART II : Modelling of radio line emission

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THE CIRCUMSTELLAR MEDIUM OF AGB STARS: A study of scattered stellar light and

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  1. THE CIRCUMSTELLAR MEDIUM OF AGB STARS: A study of scattered stellar light and molecular radio line emission PART I : A study of episodic mass loss: The detached shells of some AGB stars seen in scattered stellar light PART II : Modelling of radio line emission from circumstellar molecules in a sample of M-type AGB-variables Thesis Presentation Stockholm, 04-03-03

  2. SETTING A BACKGROUND: A schematic view of an AGB star

  3. Observations of Scattered Stellar Light * Spectroscopy Gustafsson et.al.,1997 Paper I F77 filter R Scl KI line Paper II Stokes U * Direct imaging * Imaging polarimetry

  4. Direct Imaging Observations - Telescopes: ESO 3.6m NOT - Cameras: EFOSC1 EFOSC2 ALFOSC - Coronographic mask - Filters: F59, F77 - Lyot stop Image reduction - Templates stars - Data Calibration

  5. A view of EFOSC2 in polarimetry mode

  6. CO maps: CO 10 The Targets • - Carbon stars with detached gas shells: • R Scl, U Ant, TT Cyg, S Sct, U Cam • AGB stars with detached dust shells: • U Hya, R Hya, X Tra, VX Sgr CO line profiles:

  7. Achievements * Feasibility of this type of observations * The circumstellar medium of R Scl * The circumstellar medium of U Ant

  8. Outlook - New data: U Ant S Sct - New observations with VLT, HST

  9. SETTING A BACKGROUND: A schematic view of an AGB star

  10. Circumstellar Molecules - In all type of Circumstellar Envelopes H2 - In Oxigen-rich Circumstellar Envelopes CO SiO OH H2O - In Carbon-rich Circumstellar Envelopes CO HCN

  11. Original sample: 1442 SRVs Subsample: SRVs IRVs Miras S60 ≥ 2 Jy S60 ≥ 5 Jy IRAS [12] - [25] > 1.2 91 objects 33 objects 12 objects 47 detected in CO 22 detected in CO 12 detected in CO 12 detected in SiO 28 detected in SiO 8 detected in SiO The Sample & Detection Rate

  12. Goal: CO SiO Mass loss rates Gas expansion velocities Abundances Standard CSE envelope:  - Density law: r -2 (constant M and vexp) - CSE inner radius: 1.0x1014 cm (~3R*) - Turbulent velocity: 0.5 km/s • Radiation field: A central blackbody • CMB radiation at 2.7K • Cooling processes: Adiabatic expansion • Line cooling (CO,H2O,H2 ) • Heating processes: Dust drift through gas • Photoelectric heating h-parameter The Model Code: Montecarlo code by F. Schöier

  13. Mass loss rates 12 0 -8.5 -5.5 IRVs SRVs Gas expansion velocities 25 0 20 SiO abundances IRVs SRVs 10-4 10-7 10-8 10-4 Achievements

  14. Observations: - Small sample: Interferometric maps - Large sample: Multi-line spectra Sources in the M range 10-6- 10-5 M/yr  Outlook Models: - CO : Photodissociation models Turbulent velocity - SiO : Dust modelling Cooling in the inner envelope Accelaration Envelope size

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