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

This thesis presentation delves into the circumstellar medium of AGB stars, focusing on scattered stellar light and molecular radio line emission. Part I discusses episodic mass loss and detached shells in AGB stars, while Part II involves modeling radio line emission from M-type AGB variables. The study utilizes direct imaging, imaging polarimetry, and spectroscopy techniques, with observations conducted using telescopes like ESO 3.6m. The targets include carbon stars with detached gas shells and AGB stars with detached dust shells, examining CO line profiles and achievement feasibility. The thesis sets a background with a schematic view of an AGB star and explores circumstellar molecules in various envelopes, including oxygen-rich and carbon-rich compositions. The sample and detection rates, mass loss rates, gas expansion velocities, and abundances are analyzed, supported by a Montecarlo code for modeling. Achievements include interferometric maps and multi-line spectra, providing valuable insights into the AGB stars' circumstellar environment.

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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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