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Interférométrie optique avec le Very Large Telescope - Application aux étoiles Céphéides

Abstract : Installed at the heart of the Very Large Telescope Interferometer (VLTI, located on top of the Cerro Paranal, in northern Chile), the VINCI instrument allows to combine coherently the infrared light coming from two separate telescopes. Therefore, it opens an access to very high angular resolution observations of the sky (down to a few milliarcseconds). Many important astrophysical questions will be adressed by this instrumen t: the physics of stars, protoplanetary disks and extrasolar planets, among other programs. My thesis work on the VINCI instrument has covered its conception, in particular the functionnal definition of its software system, its installation on top of the Cerro Paranal and its first scientific observations. In the first part of this document, I describe the principles of the beam combination with VINCI and its performances both in the laboratory and in real observational conditions.
In a second part, I describe the application of long-baseline optical interferometry to the study of the Cepheid variable stars. These pulsating supergiants play a fundamental role in the measurement of distances in the Universe, since it has been established that their photometric variation period it linked to their intrinsic luminosity through the famous period-luminosity relationship. The calibration of this relation requires that the distance to a number of nearby Cepheids is measured directly, unfortunately, these distances are currently poorly known, even to the closest Cepheids. The very high angular resolution allowed by VINCI and the VLTI will soon enable the refined study of the pulsation of the nearby Cepheids. By combining simultaneous observations of the radial velocity of their photosphere with angular diameter measurements, it will be possible to estimate directly their distance. The goal of this program: the calibration of the period-luminosity relationship with a precision better than 0,01 mag, a factor ten better than our current knowledge.
In addition to this fundamental program, I decribe also the possibilities offered by VINCI for the study of the main sequence dwarfs, in particular solar-type stars (with an application to the binary star Aplha Centauri A and B), and I briefly discuss the case of the extrasolar giant planets.
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Submitted on : Tuesday, February 26, 2008 - 10:03:24 AM
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Pierre Kervella. Interférométrie optique avec le Very Large Telescope - Application aux étoiles Céphéides. Astrophysique [astro-ph]. Université Paris-Diderot - Paris VII, 2001. Français. ⟨tel-00258928⟩

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