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| Paper: |
Polychromatic Interferometry of Mira Variables |
| Volume: |
378, Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes |
| Page: |
262 |
| Authors: |
Wittkowski, M.; Boboltz, D.A.; Driebe, T.; Ohnaka, K. |
| Abstract: |
We report on our project to study the atmospheric structure and circumstellar environment of evolved stars using optical and radio long-baseline interferometry. VLTI observations of the cool giants ψ Phe, γ Sge, and α Cet have previously been used to calibrate stellar model atmospheres of regular non-pulsating cool giants as well as to derive high-precision fundamental parameters. Previous VLTI observations of the Mira variable R Leo are consistent with self-excited dynamic Mira model atmospheres that include molecular shells close to the continuum-forming layers. Coordinated observations of evolved stars at near-infrared, mid-infrared, and radio wavelengths have been conducted, aiming at a better understanding of the stellar pulsation, the mass-loss process, and the triggering and formation of asymmetric structures. Results from our pilot study on the Mira variable S Ori show that the SiO masers reside at a distance of about 2 photospheric radii, a result that is virtually free of the usual uncertainty inherent in comparing observations of variable stars often widely separated in time. Preliminary results of new coordinated VLTI/midi and VLBA observations of S Ori at concurrent epochs are shown. |
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