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Atmospheric Dynamics of Red Supergiant Stars

Abstract : Thanks to their high-peak infrared luminosity, red supergiant (RSG) stars are fundamental tracers of galactic structure, efficiently probing regions of high interstellar extinction. To understand their properties is crucial and impacts a broad segment of Astrophysics.
In this thesis, the answer to the principal questions about RSGs is addressed with three-dimensional radiation hydrodynamic (RHD) models. The computer code CO5BOLD, developed by Freytag, Steffen, Ludwig and collaborators, is used.
First, I have developed a three-dimensional radiative transfer code that computes spectra and intensity maps from RHD simulations. With this tool at hand, I characterize the granulation pattern of the RHD models at different wavelengths and I study the impact of the convection on spectral line in term of line shifts and asymmetries, prospecting line bisectors and photocenter variations for future observations.
Then, I measure the characteristic atmospheric velocities. From the comparison with the observations I find that the simulations are in agreement with the observations even if the velocity amplitudes are smaller than what is observed.
Furthermore, the convection-related surface structures show an evident departure from the circular symmetry on the visibility curves and closure phases. I seek constraints of the atmospheric movements analysing these observables and I show where and how the convection pattern can be detected and measured. I conclude that today interferometers are the best way for the characterization of the convection on RSG strars.
Finally, I highlight that the principal problem of RHD simulations is the grey treatment of opacities and I explore the effects on the observables using a first non-grey testing model.
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https://tel.archives-ouvertes.fr/tel-00291074
Contributor : Andrea Chiavassa <>
Submitted on : Friday, June 27, 2008 - 12:12:48 PM
Last modification on : Monday, April 6, 2020 - 9:26:02 AM
Long-term archiving on: : Friday, November 25, 2016 - 11:50:52 PM

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  • HAL Id : tel-00291074, version 1

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Andrea Chiavassa. Atmospheric Dynamics of Red Supergiant Stars. Astrophysics [astro-ph]. Université Montpellier II - Sciences et Techniques du Languedoc, 2008. English. ⟨tel-00291074⟩

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