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Imagerie des étoiles évoluées par interférométrie; Réarrangement de pupille

Abstract : Atmospheric turbulence is an important limit to high angular
resolution in astronomy. Interferometry resolved this issue by
filtering the incoming light with single-mode fibers. Thanks to this
technique, we obtained with the IOTA interferometer very precise
measurements of the spatial frequencies of seven evolved stars. From
these measurements, we performed a blind deconvolution to restore an
image of the surface of the stars. Six of the them, Bételgeuse, $\mu$
Cep, R leo, Mira, $\chi$ Cyg and CH Cyg, feature very asymmetrical
brightness distributions. On the other hand, the Arcturus data are
extremely well fitted with a simple limb-darkened photospheric
disc. From the observations of $\chi$ Cyg, we show that the star is
surrounded by a molecular shell undergoing a ballistic motion. By
combining our dataset with spectroscopic measurements, we inferred a
mass of the star of 0.88 $\pm$ 0.04 M$_\odot$.

We propose to use the same technique of spatial filtering with
single-mode fibers to correct for the effect of turbulence in the
pupil of a telescope. Because the pupil is redundant, this technique
does require a remapping of the pupil. We developed a dedicated
algorithm to show that it was possible to reconstruct images at the
diffraction limit of the telescope free of any speckle noise. Our
simulations show that a high dynamic range (over $10^6$) could be
obtained in the visible on an 8 meter telescope. A lab experiment is
under construction to validate the concept of this new instrument.
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https://tel.archives-ouvertes.fr/tel-00128387
Contributor : Sylvestre Lacour <>
Submitted on : Thursday, February 1, 2007 - 6:11:12 AM
Last modification on : Tuesday, December 8, 2020 - 3:40:44 AM
Long-term archiving on: : Tuesday, April 6, 2010 - 8:39:48 PM

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  • HAL Id : tel-00128387, version 1

Citation

Sylvestre Lacour. Imagerie des étoiles évoluées par interférométrie; Réarrangement de pupille. Astrophysique [astro-ph]. Université Pierre et Marie Curie - Paris VI, 2007. Français. ⟨tel-00128387⟩

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